Series HF custom designed flange and insert heaters.

Transcription

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2 Page 1 - GENERAL INFORMATION A - INTRODUCTION 1 - GENERAL DESCRIPTION A Duct Heater is a self contained heater designed to be installed in the field in an air stream of a duct system, external to the air moving unit. It is designed to be installed in a duct where an adequate flow of air from a separate, interlocked fan or blower system is insured. Such a heater may be located in a main supply duct of a warm air heating system, in one of the branch ducts, or used as a room heater, at the end of a branch duct. Electric Duct heaters are an ideal answer for the heating system designer, because of electricity's inherent cleanliness as a fuel, their adaptability for use with other comfort conditioning components, such as humidifiers, de-humidifiers, electronic filters and heat pumps, and their flexibility for use with a variety of control systems to maintain the precise temperature desired. Markel has one series of Inducto Duct Heaters to accommodate all applications. Series HF custom designed flange and insert heaters. This series has built-in primary and alternate types of secondary over-temperature safety protection to meet the 1975 National Electrical Code, and UL requirements. 2-ADVANTAGES Open Coil Inducto Duct Heaters: Patent Module Design Clean Heat Double Safety Protection Low Cost Factor UL Listed Instant Heat Solid Cover for Dust Elimination Custom Design Insulated Control Panel (Standard) Low Static Pressure Drop 3 - OPTIONAL EQUIPMENT HF series are available with the following optional equipment: Built-in or Remote: Magnetic Controlling Contactors Step-down Transformers for control voltage supply Fuses for over-current protection Circuit Breakers for over-current protection Time Delays Mercury Contactors Indicator Lights Disconnect Switch Pilot Switches Pneumatic Electric Switches SCR (Solid State Devices) Three Types Secondary (back-up) Systems In this catalogue, pricing and detailed data are given regarding application and usage of the various required and optional equipment. 4 - FLEXIBLE CUSTOM DESIGN Inducto Duct Heaters are listed by the Underwriter's Laboratories Label Service Department (UL Reference Number E33694) ranging from five hundred watts to one million watts, to fit ducts from a minimum of six inch height x ten inch width to a maximum of eighty inches height x twenty feet in width. This range makes the duct heater the most versatile type of heating system. Inducto Duct Heaters are approved for zero clearance to combustible surfaces, and meet all UL, and 1975 National Electrical Code requirements. Heaters are available for 120, 208, 240, 277, 480, 550, and 600 volt electrical rating, single or three phase with control voltages of 24, , 240 or 277 volts. Inducto Duct Heaters are packaged units, completely wired for simple connection to the power supply system. With the cover removed. line terminals are completely exposed in a large terminal box. Conduit knockouts and detailed wiring diagrams are included in each unit. B - TYPICAL APPLICATIONS 1 - Prime Heating: Inducto Heaters are supplying prime heat in thousands of installations throughout the United States and foreign countries. They are used to heat all types of industrial and commercial buildings, schools, hospitals, churches, residences, and for all types of remodeling. 2 - Air Handling Equipment: Manufacturers of cooling and air handling equipment have found electric heating coils to be a valuable addition to their air handling units. Inducto Heating Coils are built to replace and fit into space provided for other types of heating coils. Usually no re-design or alteration of present equipment is necessary. 3 - Heat Pumps: Inducto Heaters are used as supplementary heat with heat pumps. When outside temperatures drop below the efficiency range of the heat pump, the heating coils provide the necessary additional heat. 4 Zoned Application: Where there is considerable heat gain or loss variation in different locations throughout a building, small blast coil heaters are actuated to compensate and prevent over-cooling. SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE 2

3 Page 2 - CONSTRUCTION A - FRAME NOTE: 'OH' can apply to overhang on either side of heater FIGURE Insert Heaters are the most generally used type because of the ease of installation in the duct system. The heating element enclosure is inserted in the air stream through a hole cut in the side of the duct, and is secured by means of screws applied from within the terminal box. FIGURE 2 The terminal compartment extends beyond the element enclosure at least 1/2 inch on all sides so that it will cover the rough opening in the duct. When additional space is required for built-in components the terminal box is extended on the air inlet side as standard, or leaving air side either up or down if specified. The "A" dimension can be extended as an overhang when specified. ****** ******** FIGURE Flanged Heaters are custom designed to be installed as an integral part of the duct system. The inside of the flanged frame is the same dimensions as the air duct, allowing for mating with, and securing to the duct flanges. A one inch flange is supplied as standard, unless otherwise specified. The flanged element enclosure and the terminal compartment are flush on the air outlet side. When "M" dimension exceeds "B" dimension, the overhang will be on the air inlet side, as standard, or leaving air side either up or down if specified. The "A" dimension can be extended as an overhang to provide space for components when specified. SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE 3

4 3 - Internally Insulated Duct Applications: Internally Insulated Ducts can affect the operation of insert and flanged duct heaters and therefore, must be specified so that the following design factors can be employed which will allow the air stream to pass over the limit controls and all elements. CONSTRUCTION. Page Bottom Terminal Box Heaters: Inducto Heaters are specially designed to accommodate installations where side mounting is not possible. Since the resistance element wire must be strung horizontally the safety controls are located in the side terminal compartment. Other controls except mercury contactors and fusing are located in bottom control box. Heaters limited to 60 KW max. Remote fusing required for all heaters over 48 Amps. Pricing under Optional Pricing Section. INSERT TYPE The element enclosure is reduced in size enough to allow the entire face of the control box to be recessed into the duct to the depth of the insulation. An angle is installed on all four sides of the terminal compartment to seal the opening and provide a mounting means. FLANGE TYPE FIGURE 7 - Bottom Terminal Box 5 - Dust Proof Terminal Box Cover: Inducto Heaters are available with a dust tight control box cover where dirt problems could affect the life expectancy of the controls. Pricing found under Optional Pricing. 6 - Multiple Heaters in a Single Duct: Inducto Duct Heaters are designed as single units in all applications except where height dimension exceeds 80". Heaters above 80" will be furnished in two or more flanged sections for stacking one on top of the other, for simplifying shipping and field installation. A special foot design is furnished with these flange units for easy mounting when stacked. Automatic A deeper flange is required so that the inside of the flanged housing is flush with the surface of the insulation and the face of the terminal compartment is recessed to the depth of the insulation. FIGURE 8 - Multiple Heaters in a single duct. 4

5 Page 4 - CONSTRUCTION resetting temperature limits are furnished in each heater section, with provisions for wiring them in series in the field. Built-in accessories, such as contactors, and fusing, are also available. Separate power lines are required for each section. When preferred, heaters with a long "W" dimension can be divided into two separate units and one installed from each side of the duct. B - DIMENSIONAL DATA The HF series terminal compartment depth "E" is normally 4 1/2", however it may be increased when necessary. The "H" and "W" dimensions are the actual duct height and width. "C" and "M" dimensions depend on several factors and must be calculated by the factory engineering department, however where conditions limit the size this must be specified. The HF series compartment has a solid cover that is hinged on the top or otherwise, also a latch is provided. A support bridge is installed on the bottom of the element enclosure on all heaters when "W" dimension exceeds two (2) feet. (See figure 1, 2 and 3). FIGURE 9-Typical Insert Heater FIGURE 11 - Bottom Terminal Box C - CORROSION PROTECTION Inducto Duct Heaters are constructed of the highest grade galvanized steel (standard), aluminized (optional). All other metal components are either zinc plated or constructed of stainless steel. This type of protection gives longer life and prevents damage by moisture from cooling systems. D-INSULATION Each heater is manufactured with a 1/2" fiberglass board insulation between the control box and the duct area. This type of insulation gives maximum protection against moisture condensation as well as thermal insulation. In installations where noise is a factor, such as high rise apartments, this type of insulation absorbs part of the air movement sound. E- HEATING ELEMENT 1 - Open Coil Type: The open coil element offers many advantages over the sheath type. One of the greatest assets is its longer life. The open coil releases its heat directly into the air stream, transferring its energy faster, and therefore operating at a cooler temperature. The sheath type element must release its energy through an insulation and the metal outside sheath. Due to this slower transfer, life expectancy is reduced and service requirements increased. In some cases, the insulation may contain voids, in which case, the conduction is reduced creating possible burn-outs. The open coil gives greater adaptability in design and lower pressure drop across the unit. This feature can help the systems designer maintain a lower static pressure, and thereby reduce the air handling power requirements, design and system costs. FIGURE 10-Typical Flanged Heater SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE 5

6 The low mass coil releases heat immediately after being energized and cools quickly after being de-energized. The low thermal inertia results in more precise temperature control. 2 - Element Construction: The Inducto Duct Heater elements are constructed of high grade resistance wire. Each element is coiled to the customer's wattage specification in our plant, assuring high quality elements with a closely controlled resistance. Each element is checked when produced, and again upon installation in the heater. Inducto heating element coils are designed for low watt density loading of the surface area of the wire (40 to 60 watts per square inch). A heavier than normal guage wire is used, giving a longer coil to maintain required resistance for a given wattage. This results in lower coil operating temperature which eliminates glow under standard operating conditions because of the greatly increased surface area and also gives a sturdier element for longer life. F - MODULAR FRAME AND CHANNEL RACK The HF series heaters are furnished with a new galvanized, (aluminized optional) modular frame. This design has made it possible for easier servicing in the field should this be necessary. The new HF channel rack has been designed to give added rigidity and also improved heat dissipation due to staggering of the rows of heating elements. (See Below) CONSTRUCTION - Page 5 G - ELEMENT TERMINATION The coil is mechanically connected to the high temperature No. 10 stainless steel terminal screw by means of a loop of element wire being sandwiched between two stainless steel washers. Since a large area of element wire is used in making the connection, burn-outs due to nicked wire at the connection are minimized. The terminal is insulated by a two piece mating male and female ceramic bushing. FIGURE 13 - Element Termination H - INSULATING BUSHINGS The high temperature special ceramic bushings, which insulate the coils from supporting metal, float freely in specially designed element racks. The floating ceramics will not crack or bind due to heating and cooling of the element. I - STEEL WELDED SAFETY SCREEN When the requirements for additional safety from possible contact to the heating elements of a duct heater, either from entering air or leaving air side, a screening material is available factory installed and UL approved as an option. Refer to Optional Pricing Section. J - ELECTRIC DUCT HEATERS FOR MULTI-ZONE APPLICATIONS For many years Inducto has been developing and manufacturing heaters for multi-zone applications. This type of application has been used in office buildings, auditoriums, schools, and many other constructions where different conditioning is required at one time. The air flows in this type of unit are controlled FIGURE 12 - Typical Channel Rack 6

7 Page 6 -CONSTRUCTION by hot deck and cold deck dampers, each having a possible air flow from zero to 100 percent. Therefore a zone calling for 100 percent heat would have its cold damper closed and the hot damper fully open. The opposite is true when 100 percent cold air is required. Two adjacent zones, serving separate sections of a building, could have the dampers in an opposite position mode. This results in a variable air flow pattern across the heating coil. Therefore, special considerations must be made when designing an electric heater for the' multi-zone application. These special design characteristics are as follows: 1 - LOW DENSITY ELEMENTS Low watt density coils are required to reduce surface temperatures to a minimum during low air flow operation. The Inducto elements are derated to one-half or less than the normal watt density. This prolongs element life and decreases radiation. 2 - MINIMUM NUMBER OF STEPS Due to the various amounts of KW required and space available in the hot decks, each application must be considered separately as to the number of steps. In any case, less than three steps are not recommended. The greater the number of steps, the greater the uniformity of temperature control. 3- FREE AREA Each multi-zone unit must have the electric heater specifically designed for its free area of air flow. All restrictions as to air flow must be considered in order to assure that all regulating and safety controls are in the air stream as well as the entire face of the heater. This assures that safety limits are able to function properly giving maximum protection and eliminating undue cycling which would decrease element life. 6 - CAPILLARY TYPE AUTOMATIC AND MANUAL RESETS Each heater contains double protection in the use of the capillary type automatic and manual reset limits. Both types of safety devices have capillaries extending the full length of the. heater and can sense thermal overload at any point along its length. Upon sensing the over temperature the unit is shut down. 7 - DISTANCE TO DAMPERS The distance between zone dampers and the coil should be at least 18 inches. If this distance is not maintained, overheating of the coil may result. 8 - CONTROLLING MEANS The stages of the heating coil should be controlled by a temperature sensing device placed in the leaving air stream. The steps of the heater should be decreased as the rise requirements are decreased. This decreases the density of the coil as less temperature rise is required and air flow decreased. All of the Inducto multi-zone heaters are constructed with open coil elements because of their better operating characteristics over the finned tubular elements. These advantages are discussed on page 10 section II Construction - paragraph E. The combination of Inducto multi-zone heaters and multi-zone units should be made in accordance with NEC and local governing codes. The Inducto multi-zone heaters will be built in accordance with Underwriters Laboratories Standards; however, they will not bear the UL label due to the vast testing required of the many different combinations. 4 - ELIMINATION OF STRATIFICATION In order to prevent stratification and use the maximum amount of air flowing across the coil, each step should have a spread across the full face of the heater. This is necessary especially when only one or two dampers are open. 5-BAFFLE PLATES Perforated baffle plates should be provided on the air inlet side of the heater to assure an even air distribution across the face of the coil. This is an important function in low air flow usage of the coil. SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE 7

8 INSTALLATION DESIGN AND PROCEDURES - Page 7 A-GENERAL DESIGN INFORMATION EXAMPLE B TEMPERATURE RISE VELOCITY (FPM)-WATT DENSITY (KW PER The air temperature rise through the heater is 9 SQ. FT.) To find the watt density (KW per sq. factor of great importance. The chart should be ft.) at a given temperature rise and F.P.M. of air, consulted for the temperature rise expected to use bottom and left scales. result from the air flow and watt density used. EXAMPLE: To find the heat input in a duct handling 700 F.P.M. of air, with a temperature 1 - The Temperature Rise Chart (Fig. 1) aids rise of 60ºF. in calculating requirements or results from the 1. Draw a line vertically up from the 700 known factors of FPM, CFM, Temperature Rise, F.P.M. on the bottom scale to the 60 F. Total KW, or KW per square foot. If two related temperature rise line. factors are known, the others can be 2. From the point of intersection draw a determined. horizontal line to the left side scale giving CFM 13.5 KW per sq. ft. of duct area. 2 - Minimum Velocity Requirements: Electric duct heaters are different from steam or hot water coils, in that the B.T.U. output remains constant as long as the heater is energized. To eliminate over-heating and burn out due to low air velocity, an automatic re-set temperature limiting control is built into each heater. The minimum velocity required to prevent nuisance tripping of the temperature limiting control is determined from the air velocity chart (Fig. 2 on the basis of entering air temperature, and watts per square foot of cross sectional duct area. FIGURE 1 NOTES: (A) For values above or below those on the scale, multiply or divide the known factors by a convenient number. Make the necessary calculations on the chart, then multiply or divide the answer by the original number for the actual value. (B) If any two factors are known the third may be calculated in a similar manner. EXAMPLE A Air (CFM)-(KW) Total Heat Required To find the total heat required at a given temperature rise and CFM, use the top and right scales. EXAMPLE: The heat required to achieve a 40 F temperature rise in a duct handling 12,000 C.F.M. 1. Draw a line vertically down from the 12,000 C.F.M. on the top scale to the 40 F. temperature rise line. 2. From the point of intersection draw a horizontal line to the right side scale. Giving total heat required 150 KW. CAUTION - DO NOT OPERATE WITHOUT PROPER AIR FLOW For efficient and trouble free operation it is important that air flow be adequate over the complete heating area and particularly at element terminals. No electric duct heater should ever be operated with insufficient air flow because overheating and subsequent malfunction may result. The minimum air velocity required at any point should be determined from the graph following. MINIMUM AIR VELOCITY REQUIRED FOR PROPER OPERATION Formula: H X W divided by 144 = sq. ft. /area KW divided by area = KW/sq. ft. duct area (density) H = Element Frame Height W = Element Frame Width 8

9 Page 8 - INSTALLATION DESIGN AND PROCEDURES 3 - Available Watt Density: "HF" series Inducto Duct Heaters are built to the wattage and dimensions as specified by the customer. The "HF" series heaters are available to 1000 KW in all wattages up to 20 KW per square foot of cross sectional duct area and are suitable for installation with zero clearance to combustible surfaces and up to 100 degrees Fahrenheit inlet temperature. These heaters are available through 20 feet in width. C - INSTALLATION RESTRICTIONS The following are stated requirements of UL regarding installation of duct heaters. B - INSTALLATION RECOMMENDATIONS 1 - Should be installed at least 4 feet from a heat pump or central air conditioning unit. FIGURE 3 FIGURE No clearance is required between the duct and combustible surfaces around the duct for Inducto "HF" series duct heaters. FIGURE 4 1 -The heater must be installed to assure equal air flow through the entire face area of the heater. Refer to N EC par FIGURE A duct heater must not be installed so that the heating element coils are strung vertically through the supporting racks. FIGURE A canvas vibration insulation connector should not be located less than 18 inches from a duct heater. If it is located closer, an asbestos connector should be used. DUCT HEATER PRESSURE DROP SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE 9

10 INSTALLATION DESIGN AND PROCEDURES Page 9 Series HF INSTALLATION. OPERATING AND MAINTENANCE INSTRUCTIONS FOR INDUCTO ELECTRIC DUCT HEATERS APPLICATION REQUIREMENTS 1. The duct system must provide uniform air flow over the entire face area of the heating elements. 2. For satisfactory and safe operation the minimum air velocity must be maintained as determined from table. 3. The air duct should be installed in accordance with the standards of the National Fire Protection Association for the installation of air-conditioning and ventilating systems of other than residence-type (Pamphlet No. 90A) and residence-type warm air heating and air-conditioning systems (Pamphlet No. 90B). 4. The heater should be installed at least 48 in. from the duct flanges of a heat pump or central air conditioner. 5. Maximum inlet air temperature is 100 F. 6. Series HF heaters may be installed in duct systems having zero clearance to combustible surfaces. 3. Insert Type (Fig. 1) - Cut a hole in the side of the duct 1/8" larger than the element housing (H-1 x C) and insert the heater. Attach the back of the terminal box to the duct. 4. Flanged Type (Fig. 2) - Provide duct flanges to match heater flanges. Attach the heater to the duct flanges with screws. INSTALLATION PROCEDURES 1. Make sure air flow arrow on heater corresponds to air flow through the duct and heater is properly positioned if marked with "top." 2. The heater terminal compartment should not be enclosed by insulation, etc. HF

11 Page 10 - INSTALLATION DESIGN AND PROCEDURES ELECTRICAL WIRING INSTRUCTIONS WARNING: DISCONNECT ALL POWER SOURCES BEFORE DOING ANY WORK ON THE HEATER INSTALLATION. 1. Use the wiring diagram supplied with the heater as a guide in correlating field wiring with the heater internal wiring. If there is more than one heating step, wire the unit so the steps are energized in the same sequence as numbered in the heater. 2. All field wiring to the heater must meet the requirements of the N.E.C. and applicable local codes. 3. Wiring to the heater must be rated for 75 C. minimum. 4. Supply conductors must be sized to carry at least 125% of the ampere load of the circuit it supplies. 5. For low voltage control circuits, use NEC Class 1 wiring as described in Article 725 of the National Electrical Code. 6. The fan must be interlocked with the heater so that the heater is not energized unless the fan is on. A typical method of accomplishing this is shown on the wiring diagram, if it is not built in. 7. If contactors are field supplied, they must have adequate ratings for the load carried and be UL listed for 100,000 cycles of operation. Do not exceed the control circuit volt-ampere rating marked at the control terminal block. 8. If heater does not have a built-in disconnect switch or main circuit breaker, install a remote disconnect (furnished by others) in accordance with the National Electrical Code, Article Do not bundle, tie or wrap power wiring in groups as this may cause over-heating and eventual breakdown of insulation. 10. For low voltage control circuits using two supply transformers with a heating-cooling thermostat, one for heating and one for cooling, a thermostat with isolating contacts must be used to prevent interconnection of the two different circuits. Caution: For successful service using aluminum wiring, special treatment of all connections is an absolute necessity in order to prevent high resistance and oxidation problems. For recommended practice check with your local electrical utility. OVERCURRENT PROTECTION UL requires compliance with paragraph (b) of the National Electrical Code as follows: "Electric space heating equipment employing resistance type heating elements rated more than 48 amperes shall have the heating elements subdivided. Each subdivided load shall not exceed 48 amperes and shall be protected at not more than 60 amperes." This means that sub-circuit overcurrent protection must be provided if the total heater load exceeds 48 amperes. If overcurrent protection is not built-in, all heaters exceeding 48 amperes total line current are divided into a sufficient number of sub-circuits, each provided with line terminals for connection to remote overcurrent protection. MAXIMUM KW PER CIRCUIT FOR OVER-CURRENT SIZING OF SUPPLY CONDUCTORS The required minimum size of supply conductors is marked at the field wiring terminals within the heater control box, however for reference the following table is included. The wire gauges are calculated for 125% of the heater line current as required by the National Electrical Code, Article (b) based on conductor insulation rated for 75 C (167 F) (1) For 7-24 conductors in a raceway or cable reduce allowable heater line currents to 87 ½ % of those shown above. (2) Based on 30 C (86 F) ambient temperature. For higher ambient temperature, see N.E.C. table and Note 13. (3) Based on 80% of ratings in table N.E.C. for 75 C insulation. (4) Based on 80% of ratings in table N.E.C. for 75 C insulation. CALCULATION OF LINE CURRENTS (AMPS) To determine the line current, use the following formulae: Two or more circuits may be paralleled to make one heating stage. SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE 11

12 ELECTRICAL DESIGN - Page 11 A - GENERAL The requirements and practices described below are based on the National Electrical Code and the Space Heating Standard of the Underwriters Laboratories, Inc. (UL). Although UL requirements are uniform throughout the country, local electrical codes may deviate from the National Electrical Code, therefore local inspection authorities should be consulted regarding local requirements. After final assembly and before shipping each Inducto duct heater must pass a 2000 volt minimum dielectric test. 3 - Ohm's Law 1 - Effect of low voltage on wattage and B.T.U.: The heating elements may be used on voltages lower than the design voltage of the heater, however, the wattage and B.T.U. output will he reduced to the percentage listed in table 1. DE-RATED WATTAGE FOR LOW VOLTAGE Heater Voltage Line Voltage TABLE 1 % of Heater Wattage & B.T.U. 92% 84%, 92% 84% 92% 84% 75% 69% 92% 83% 92% 84% 2 - Standard Voltages: Inducto duct heaters are built in five standard voltage ratings to cover the voltage ranges listed in Table 2. If a specific voltage is required, the order must be marked "specific voltage - V." For heater output on reduced voltage see Table 1. FIGURE 1 Ohm's Law Equation Wheel This "wheel" shows the equation for calculating any one of the basic factors of electricity - Watts (W). Amperes (I), Volts (E) or Ohms (R) - when any two of these factors are known. The elements to be calculated are shown on the rim of the wheel. Each quadrant shows three equations for solving the unknown; select the equation appropriate for the known values. Example: a 2400 Watt Single Phase heater is connected to a 240 Volt circuit. How many Amps does it draw? Solution: Since we are finding Amps, the formula will be found in the I (Amperes) section of the wheel. W/E = 2400 W 240 V = 10 Amps What is the Resistance? E 2 /W = R 240 V x 240 V 2400 W = 24 Ohms STANDARD VOLTAGES If you order: You will get: 110 V 115V., etc. 120 V. 208V 208 V. 220V 230V, 236V, etc. 240 V. 254V 265V, 277V. 277 V. 440V 460V, etc. 480 V. Ratings from 500 V. up as to 600V. will be furnished ordered. TABLE 2 12

13 Page 12- ELECTRICAL DESIGN 4 - ELECTRICAL CODES AND REGULATIONS - The design and installation of electric duct heaters must conform to all codes and regulations apply ing at the job site in addition to meeting the specifications. These include standards and requirements published by Underwriters' Laboratories. Inc. (UL), National Electrical Code (NEC). and other state and local agencies. Ductwork must be installed in accordance with one of the following standards of the National Fire Protection Association: Installation of Air Conditioning and Ventilating Systems (1972 Pamphlet 90A), or Residence Type Warm Air Heating and Air Conditioning Systems (1968Pamphlet 90B). NATIONAL ELECTRICAL CODE Paragraph Approved. Heaters installed in an air duct shall be identified as suitable for the installation. Paragraph Air Flow. Means shall be provided to assure uniform and adequate air flow over the face of the heater. Heaters installed within 4 feet of a fan outlet, elbows, baffle plates, or other obstruction in duct work may require turning vanes, pressure plates, or other devices on the inlet side of the duct heater to assure an even distribution of air over the face of the heater. Paragraph Elevated Inlet Temperature. Duct heaters intended for use with elevated inlet air temperature (such as heat pumps) shall be approved for the purpose and so marked. Paragraph Installation of Duct Heaters with Heat Pumps and Air Conditioners. Heat pumps and air conditioners having duct heaters closer than 4 feet to the heat pump or air conditioner shall have both the duct heater and heat pump or air conditioner approved for such installation and so marked. Paragraph Condensation. Duct heaters used with air conditioners or other air-cooling equipment that may result in condensation of moisture shall be approved for use with air conditioners. Paragraph Fan Circuit Interlock. Means shall be provided to insure that the fan circuit is energized when the first heater circuit is energized. However, time or temperature controlled delay in energizing the fan motor shall be permitted. INDUCTO QUALIFICATIONS Inducto duct heaters are designed to comply with the provisions of the National Electrical Code, UL, and other regulations. Compliance with this requirement is the responsibility of the system designer and installer. Minimum air velocities for Inducto heaters are shown in the installation instructions. Inducto heaters are approved for use with heat pumps. Critical performance data for each heater is clearly indicated on the heater as well as in the installation instructions. Lower watt density heaters may be specified for special applications. This pertains to the design and installation of heat pumps rather than to duct heaters. Inducto does recommend that a duct heater should be installed at least 4 feet downstream from heat pumps and air conditioners and at least 2 feet downstream from air handlers. All Inducto duct heaters are assembled with a 1/2" fiberglass board insulation permanently attached to the duct side of the control compartment as standard. This construction provides maximum protection against condensation. These heaters are UL listed and marked - "For use with heat pumps or central air conditioners." Inducto heaters are available on order with a built-in airflow switch, or fan interlock relay. SPECIFICATIONS SUBJECT TO CHANGE WITHOUR NOTICE 13

14 Paragraph Limit Controls. Each duct heater shall be provided with an approved, integral, automatic-reset temperature-limiting control or controllers to de-energize the circuit or circuits. In addition, an integral independent supplementary control or controllers shall be provided in each duct heater that will disconnect a sufficient number of conductors to interrupt current flow. This device shall be manually resettable or replaceable. Paragraph Location of Disconnecting Means. Duct heater controller equipment shall be accessible with the disconnecting means installed at or within sight from the controller. Paragraph Controllers and Disconnecting Means. (a) Thermostats and thermostatically controlled switching devices that indicate an off position and interrupt line current shall open all ungrounded conductors when the control device is in this off position. (b) Thermostats and thermostatically controlled switching devices that do not have an off position shall not be required to open all ungrounded conductors. (c) Remote-control thermostats shall not be required to meet the requirements of (a) and (b) above. These devices shall not be considered as the disconnecting means. (d) Switching devices consisting of combined thermostats and manually controlled switches that serve both as controllers and disconnecting means shall: (1) Open all ungrounded conductors when manually placed in the off position. (2) Be so designed that the circuit cannot be energized automatically after the device has been manually placed in the off position. Paragraph Overcurrent Protection. (b) Resistance Elements. Electric space heating equipment employing resistance-type heating elements rated more than 48 amperes shall have the heating elements subdivided. Each subdivided load shall not exceed 48 amperes and shall be protected at not more than 60 amperes. (c) Overcurrent Protective Devices. The overcurrent protective devices specified in (b) above shall be: (1) factory-installed within or on the heater enclosure or provided as a separate assembly by the heater manufacturer; (2) accessible, but shall not be required to be readily accessible; and (3) suitable for branch-circuit protection. ELECTRICAL DESIGN - Page 13 All Inducto standard and custom duct heaters include a primary auto-reset high limit switch and a secondary disc type replaceable - all readily accessible in the heater control compartment. Inducto custom heaters may be ordered with a factory installed electrical disconnect switch sized to the total heater capacity (200 amp max. per switch). Inducto heaters are furnished with built-in contactors and other control devices for total disconnect of all ungrounded conductors or for circuit de-energizing. Circuit de-energizing will normally be furnished. To meet this requirement, Inducto heaters are available with built-in fusing and circuit breakers. All heaters exceeding 48 amperes total line current are divided into subcircuits (as allowed by stages) of less than 48 amperes and are protected at not more than 60 amperes. The main conductors supplying these overcurrent protective devices are considered branch circuit conductors and are subject to the 125% ampere rating rule. 14

15 Page 14- ELECTRICAL DESIGN 4 - Electrical Codes and Regulations (Cont.) Underwriters Laboratories Inc. Standards for Safety No UL REQUIREMENTS TRANSFORMER PRIMARY OVERCURRENT PROTECTION Overcurrent protection at not more than 20 amperes shall be provided by a suitable circuit breaker or fuses, as a part of the heater, (1) for each general-use duplex receptacle circuit, (2) for each transformer primary circuit, except as indicated in paragraph 17.14, and (3) for each lampholder circuit, except as indicated in paragraph 17.12, independent of a heating element, unless the heater would be properly connected in accordance with the National Electrical Code to a branch circuit rated at 20 amperes or less. See para graph The overcurrent protection may be omitted from the primary of a Class 2 transformer A heater intended for use of a 15 or 20 ampere circuit, as indicated in paragraph 7.12, shall be marked; Use Only On a Ampere Branch Circuit. a The number 15 or 20 as appropriate. FACTORY INSTALLED CONTROLS INDUCTO QUALIFICATIONS Inducto Heaters are provided with a control transformer when specified or requested. When a control transformer is built-in to a heater or remote control panel the primary of the transformer will be protected per code and the standard requirement is: (a) Class II trans. are integrally protected and will be additionally protected only when specifically requested, (b) All other transformers will be connected within the heater to a circuit of 16 amp. maximum if available, otherwise separate primary fusing will be installed. Though not required the secondary of the transformer will be fused if specified A contactor or similar device, such as a silicon controlled rectifier, required for use with a limit control shall be provided by the manufacturer of the heater, but need not be mounted on the heater. See paragraph If required overcurrent protective devices or contactors are provided as a separate assembly, see paragraphs 17.2 and 23.12, the heater shall be marked to indicate that it is to be used only with this separate assembly The overcurrent protective devices required by paragraph 17.1 shall be provided as an integral part of the heater or shall be provided by the heater manufacturer as a separate assembly, for independent mounting, for use with the heater. See paragraph In some applications the required components cannot be built in the duct heater terminal box because of space limitations, inaccessibility, etc. In this case some, or all, of the components can be mounted and factory wired internally, as applicable, in a panel for remote mounting. All terminals are marked to clearly indicate the field connections between the panel and the heater. The panel is of the same construction as the heater terminal box and the same components will be used as previously described in this catalogue for use in the Inducto duct heater. Both the heater and the remote control panel must be UL listed, so labeled, and completely coordinated. SPECIFICATIONS SUBJECT TO CHANGE Wl TH OUT NOTICE 15

16 CONTROL COMPARTMENT COVER 5.11 Except as indicated in paragraph 5.13, the door or cover of an enclosure shall be hinged (1) if it gives access to any fuse, circuit breaker, or manually resettable temperature control in other than a low-voltage circuit, and (2) if uninsulated live parts are exposed during the normal replacement of the fuse or resetting of the manually resettable device. Such a door or cover shall also be provided with an automatic latch, see paragraph 5.15, or the equivalent and, if live parts other than the screw shell of a plug fuseholder are exposed inside the enclosure, a captive screw or equivalent means, requiring the use of a tool to open, to reliably secure the door or cover in place. See paragraph A spring latch, a magnetic latch, a dimple, or any other mechanical arrangement that will hold the door closed, and would require some effort on the user's part to open it, is considered to be a suitable means for holding the door closed as required in paragraph The captive screw may be omitted from the door or cover over the compartment housing the uninsulated live parts if it is provided in the cover that must be opened to gain access to the door or cover. Arrangements employing two mating hinged doors are acceptable where the automatic latch and captive screw are provided only on one door (1) if that door is designed to be opened first and closed last, and (2) if the latch and screw will hold the other door closed. ZERO CLEARANCE 44.2 If spacings between combustible material and the duct in which a duct heater is installed must be no less than a specified distance to prevent attainment of hazardous temperatures on that material, the heater shall bear a suitable warning marking to convey this information. See paragraph A duct heater rated 50 kilowatts (kw) or less shall be suitable for installation with zero spacing between the duct and combustible surfaces. A duct heater rated more than 50 kw may necessitate that such spacings be larger than zero. ELECTRICAL DESIGN. Page 15 All Inducto duct heater control compartments. whether integral or remote, are provided with a piano type hinge on the longest cover dimension or on any side specified. All covers are provided with an approved latch requiring a tool to open and a pull ring to facilitate opening the cover. All covers over 48" long are provided with two latches and pull rings. Inducto Heaters Series "HF" are UL listed for zero clearance up to 1000 KW. 16

17 Page 16- ELECTRICAL DESIGN 5 - Power Wire Sizing: If a long run of wire is required or more than three wires are run in a conduit the allowable capacity on a given wire size must be reduced as per NEC requirements (see note 13 to NEC Table and ) MAXIMUM AMP LOAD ALLOWED ON VARIOUS WIRE SIZES FOR. FIELD WIRING TO DUCT HEATERS De-Rated 20% TABLE 3 B - HEATER POWER CIRCUITRY See wiring diagrams for details of the various wiring systems mentioned below. All stages of a heater are of equal KW unless specified otherwise. For pricing of unequal stages, see Pricing Section. 1 - Single phase power circuits: Each circuit consists of a heating coil (or coils connected parallel) which cannot exceed 48 amp for over-current protection. A single stage heater may be controlled directly by a line voltage thermostat without using a controlling contactor if the heater rating is within the rating of the thermostat, the over-temperature protection controls and the fan interlock. Larger loads are controlled by contactors, S.C.R. controllers or load carrying step controllers. 2 - Balanced Three Phase Power Circuits: Each circuit cannot exceed 48 amp for over-current protection and consists of three (or a multiple of three) heating coils factory connected in delta or wye system at the factory's option. The load will be balanced (equal) among the three phases and the entire circuit is controlled as a unit and operates identically whether the power source is three or four wire. Therefore a neutral terminal is not furnished on balanced circuits. Each circuit is normally controlled by a contactor which in turn is controlled by a thermostat or step controller in the control circuit. TABLE 4 Except From Table 3A - NEC - Maximum Number of Conductors in Trade Sizes of Conduit or Tubing (Based on Table 1, Chapter 9) SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE 17

18 ELECTRICAL DESIGN - Page 17 TABLE 5 TOTAL AMPERAGE RATING CHART K.W. Rating B.T.U.H. 208 AMP Volts Rating 220 AMP Volts Rating 230 AMP Volts Rating 240 Volts AMP Rating 277 Volts AMP Rating 440 Volts AMP Rating 480 Volts AMP Rating 1 PH 3 PH 1 PH 3 PH 1 PH 3 PH 1 PH 3 PH 1 PH 3 PH 3 PH 3 PH 0.5 1, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Volts AMP Rating 18

19 Page 18. ELECTRICAL DESIGN TOTAL AMPERAGE RATING CHART (CONT'D) K.W. Rating B.T.U.H. 208 Volts AMP Rating 220 Volts AMP Rating 230 Volts AMP Rating 240 Volts AMP Rating 277 Volts AMP Rating 440 Volts AMP Rating 480 Volts AMP Rating 550 Volts AMP Rating 1 PH 3 PH 1 PH 3 PH 1 PH 3 PH 1 PH 3 PH 1 PH 3 PH 3 PH 3 PH , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE 19

20 As standard practice balanced three phase circuits will be furnished for three phase power unless single phase circuits from three phase power are specified. 3 - SINGLE PHASE CIRCUITS FROM THREE PHASE POWER SUPPLY If the power supply to the heater is three phase and the heater circuits are to be controlled by: load carrying switches of a step controller, single phase S.C.R. controllers, or similar load carrying device, single phase circuits from three phase power must be specified. Whether the power supply is three or four wire system must also be / specified. For three wire systems each circuit is connected between alternate pairs of phases using the delta configuration. When any multiple of three circuits are heating, the load will be balanced. For four wire systems each single phase circuit is connected between one phase and the neutral using alternate phases for consecutive circuits. NOTE: Some SCR controllers or load carrying step controllers cannot accept the automatic over-temperature limits in a control circuit to de-energize the heater immediately should an over-temperature condition occur. If this is the case, magnetic contactors, which are controlled by the primary, automatic, over-temperature cutouts, must also be connected in the load circuit to de-energize the heater preventing over-heating. C - BUILT-IN COMPONENTS 1 - Internal Heater Wiring: All factory wiring is UL labeled. 105 C thermoplastic insulated, copper appliance type wire. As a result of UL testing the following has been established as the maximum load per wire size on factory wiring within the heater (does not apply to field wiring): 12 AWG 30 Amp maximum 10 AWG 40 Amp maximum 8 AWG 48 Amp maximum ELECTRICAL DESIGN - Page Overcurrent Protection: The NEC par states: (b) Resistance Elements. Electric space heating equipment employing resistance-type heating elements rated more than 48 amperes shall have the heating elements subdivided. Each subdivided load shall not exceed 48 amperes and shall be protected at not more than 60 amperes. (c) Overcurrent, Protective Devices. The overcurrent protective devices specified in (b) above shall be: (1) factory-installed within or on the heater enclosure or provided as a separate assembly by the heater manufacturer; (2) accessible, but shall not be required to be readily accessible; and (3) suitable for branch-circuit protection. Where cartridge fuses are used to provide this overcurrent protection, a single, disconnecting means shall be permitted to be used for the several subdivided loads. Fuses and circuit breakers are available with the heaters, to meet the above requirements, either built in the terminal box or built in a panel for remote mounting (see "D - Remote Control Panels"). The overcurrent protection (fusing or circuit breakers) must be sized at least 125% of the circuit load it protects. For example, 60 amp fuses are required for a 48 amp load. The maximum KW allowed per various voltages is shown in table 6. For heaters drawing 48 amp or less total load, the branch circuit fusing at the distribution panel usually meets the NEC requirements, however, supplementary fusing for each stage within the heater can be furnished if specified. As standard practice, small stages will be grouped to a maximum of 48 amp and fused as one circuit. This conserves space and is more economical while meeting all NEC requirements, however, each stage will be protected separately when specified. Dual element fuses are available when specified. See Pricing Section. MAXIMUM KW PER CIRCUIT FOR OVER- CURRENT PROTECTION (48 Amp) Two or more circuits may be paralleled to make one heating stage. TABLE 6 FIGURE 2 - Typical Fuse block 20

21 Page 20- ELECTRICAL DESIGN FIGURE 3 -Typical Circuit Breaker 3 - Power Supply Connections: A heavy duty terminal block, or blocks, are provided in Inducto Duct Heaters for each field wiring connection for both control and power circuits. The number of power supply circuits required to a duct heater may depend on the components that are built in. See built-in fusing and contactor sections, IV-C-2 and IV-C-4 for an explanation of our standard practice. All field connection terminal blocks are designed to accommodate either copper or aluminum conductors as required by NEC and UL INSTRUCTIONS RECOMMENDED PROCEDURE FOR ALUMINUM TERMINATIONS GENERAL To help guard against overheating, the following procedure is recommended when connecting aluminum wire. PROCEDURE Step 1. Strip the wire of its insulation to the desired length without ringing or nicking the wire. Step 2. Wire brush the stripped portion of conductor thoroughly. Step 3. Thoroughly coat stripped conductor with oxide inhibiting compound. (Two recognized compounds are Penetrox A and Alnox-UG. There may be others available which will do equally well.) Step 4. Insert the conductor into the connector making certain all strands are contained and tighten the connector screws securely. This operation should result in the compound oozing out from between the individual strands of the conductor. If this does not happen, this is an indication that an insufficient quantity of compound was used. Step 5. Wipe excess compound from area adjacent to connection because some compounds contain metallic particles and could reduce the dielectric strength of the insulating materials employed. FIGURE 4. Typical Power Terminal Block Special Feature - When several sub-circuits are required to be fed from one main power supply terminal, a bus bar type terminal block is used to eliminate the problems associated with having multiple wires under one lug. 4 - Built-in Magnetic Contactors: For use as primary controlling contactors and for secondary (backup) contactors (see secondary protection). Contactors are built-in only when specified. One, two, three and four pole are available with ratings as shown in figures 5, 6, and 7 and with holding coil voltages of 24, 120, 208/240, or 277V. The holding coil data, symbol and part number (where applicable) are also listed with the figure. All are UL listed as control components, having successfully passed the 100,000 cycle test under 150% of full rated amp load. The NEC requires that Duct Heater Controlling Contactors shall be accessible. In the definite purpose line the different voltage coils are easily interchangeable among all the sizes used. When controlling contactors are built in without built-in over-current protection, a power line SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE 21

22 terminal block will be provided for each group of stages (or stage) not exceeding 48 ampere total, keeping to a minimum the number of field installed supply circuits required, while allowing for proper fusing in the field as required by both UL standards and the NEC. This means that heaters 48 amp or less will require only one power supply circuit. However, when specified that. each stage is to be field wired with a separate circuit for individual fusing, a terminal block is provided for each stage for field connections. STANDARD USAGE PRACTICE Our standard practice when contactors are built in, for controlling and/or backup duty, is to de-energize the circuit only. That is, to use contactors that will open only enough power lines to interrupt the flow of current to that stage being controlled. Contactors must be used that will disconnect all ungrounded conductors of the circuit in some cases, such as: (a) local or state requirements, (b) if the control or thermostat is marked with "OFF," (c) by engineering specification. If any of these conditions exist, disconnecting type contactors must be specified when ordering. For contactor pricing refer to Pricing Section. ELECTRICAL DESIGN - Page 21 FIGURE 6 - THE SINGLE POLE CONTACTOR is a totally enclosed unit with a rating of 18 amps resistive and 2 HP inductive at 250 volts. Coil Data: 10 VA inrush - 5 VA holding MERCURY CONTACTORS: This type of contactor should be used in applications where minimum noise is a definite factor or where rapid cycling control systems are used. These units are rugged with all moving parts totally sealed within a tube, eliminating all exposed arc. All mercury contactors, must be installed in an upright position, therefore the direction of air flow through the duct must be specified when specifying this type of contactor. See Pricing Control circuit voltages available are 24, 120, 208/240, and 277 volt. FIGURE 5 DEFINITE PURPOSE CONTACTOR: Available in 25,30,40 and 50 amp resistive rating with heavy duty contacts and encapsulated coil which resists oil, dirt, moisture and mechanical damage. Holding Coil Coil Voltage 24V 110V 208/ 277V 480V 240V Contactor symbol VA inrush VA holding Replacement part No. 55-2G G2 55-2G3 55-2G G4 FIGURE 7 - Typical Three Pole Mercury Contactor Holding Coil Data No. of Inrush Holding Series Poles VA VA BF BF BF BFC BFC BFC

23 Page 22 - ELECTRICAL DESIGN 5 - Fan Interlock Options: Effective January 30, 1974, all Inducto heaters must be furnished with a type of fan interlock. The Inducto standard will be a differential pressure switch. A - Differential Pressure Switch. (Standard): The differential pressure switch is available built-in to the terminal box compartment UL approved. This has become a very popular method. This is an excellent application when constant fan is used. B - Electrical Interlock: A one pole contactor interlock will be built in, wired to energize the fan circuit when the first stage of the heater is energized. (See wiring diagrams number E2-A, B & C). For pricing refer to Pricing Section. gives for longer life of the control. The heater elements are controlled simultaneously, no sequencing of steps, which means there is no possibility of air stratification. Several slave controls can be used with one master control and thermostat. B - Description: These UL listed solid state proportional controllers consist of a triac assembly mounted on a heat sink. These specially designed SCR's have the triac assembly mounted inside the terminal box and the heat sink is attached to the outside of the terminal box. The heat sinks are in the open air where there is good convection cooling, keeping the inside of the terminal box at a normal temperature. Inducto heaters with built-in SCR's can be used with the air entering on either side. A special UL listed solid state thermostat must be furnished when ordering any combination of SCR's. Power output is controlled from 0 to 100% and is infinitely variable in direct proportion to thermostat output. All elements in the heater are controlled simultaneously avoiding problems of air stratification. See Pricing Section. FIGURE 8 Typical Differential Pressure Switch 6 - SCR Controllers A - Application and Advantages: These solid state proportional controllers are ideal for application in schools, libraries, offices and hospitals where noise is a factor. Since they are all solid state there are no moving parts, which Thermistor Type Thermostat C - Thermostat: A wall mounted vertical or horizontal thermistor type thermostat model with manual "On" and STBY (stand-by) must be used with each Master SCR. Thermostat range is 65 F to 85 F proportional band is 2 F. (Full heat demand will actuate on a 2 F change.) Any smaller change will cause a proportionately smaller SCR output. Accuracy of thermostat is - ± 1 F. Remember: No other commercial thermostat can be used. For applications requiring either a duct thermostat or a pneumatic system, consult factory. D - Safety Contactor: Safety contactors UL listed must be installed in front of and in line with the SCR's unless the automatic reset thermal cutout can carry the load. All three phase heaters must be furnished with a safety contactor. FIGURE 9 Duct Heater SCR - (Solid State) SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE 23

24 Any single phase heater exceeding the following ratings must have safety contactors. AUTOMATIC 277V, Single Phase THERMAL CUTOUT 240V, Single Phase R ATINGS 2.1KW@ 208V,Single Phase 1.8KW@ 120V, Single Phase Control Voltage: This SCR system generates its own control voltage for operation of thermostat. Safety contactors holding coils can be operated direct from line voltage up to 277 volts, single phase when 480 volt three phase is required a step-down transformer must be furnished. 7 - Disconnect Switches: The National Electric Code states that there must be a disconnecting means at or within site of the controlling means. Disconnect switches can be field supplied or can be built into the heater integral control panel or remote control box. We offer two types of disconnect switches. Door interlock type (fig. 11) or toggle type without door interlock (fig. 11 a). Both devices meet the requirements of the N.E.C. Door interlock switches are snap-action type with the operating handle mounted in the hinged cover and interlocked to open only when in the off position. Toggle type switches are mounted on the side of the control panel and kills all power in the heater when in the off position. ELECTRICAL DESIGN - Page Micro De-energizing Switch: Electrical de-energizing switch for control circuit. Plunger type switch wired into control circuit of heater to automatically de-energize the control circuit when door is opened. Switch is single pole double throw rated at 15 amps up to 480 v non-inductive; 1/8 HP at 125 volts, 1/4 HP at 240 volts inductive. Alternate switch is available for line volts over 480. Switch is rated at 10 amps up to 600 volts non-inductive and 6 amps at. 115 volts; 3 amps at 230 volts; 1.5 amps at 480 volts and 1.2 amps at 575 volts inductive. Both UL and NEC require that the contactors be the disconnecting type when this type of switch is used. This switch does not serve as the disconnect switch as required by the NEC. See Pricing Section. FIGURE 12 - Typical Pressure Type Micro Switch FIGURE 11 A Typical Toggle Disconnect Switch 9 - UL and NEC Safety Requirements: (a) Primary over-temperature protection (cutouts) Standard Disc Type: As standard practice all Inducto Duct Heaters incorporate, as part of the basic heater, one or more disc type, automatic resetting temperature limiting devices (Fig. 13). When a higher than normal temperature condition occurs within the heating area and the bi-metal disc reaches 170 F. the cutout opens de-energizing the heater. After cooling, the heater is automatically energized to continue service. The limit control is a UL listed temperature limiting component having passed the 100,000 cycles of operation test under 150% of full rated load. It may be wired in the power circuit of single phase heaters not exceeding its rated capacity and in the control circuit, for pilot duty, on larger single phase and all three phase heaters. The resistive rating is 25 amperes and the pilot duty rating is 125VA at 120, 240 or 277 Volts AC. FIGURE 11 - Typical Disconnect Switch with Operating handle. 24

25 Page 24 - ELECTRICAL DESIGN (1) This type of secondary over-temperature protective device has to be replaced to reactivate the heater following correction of the problems discussed above. Two types are available. They may be wired in line (load carrying) up to their rated capacity of 48 amps, using enough cutouts to de-energize the heater. They may also be wired for pilot duty using one for the entire heater to control backup contactors which are independent of the primary controlling contactors. (See backup contactors below.) FIGURE 13 -Disc Type FIGURE 14 - Capillary Type Capillary Type Cutouts (Special): On heaters for ducts exceeding 10 feet in width a capillary type automatic resetting limit control is required. In addition, if the duct is also over 40 inches in height two are required. This device has a capillary temperature sensing element which is mounted along the heating element enclosure giving protection across the entire width of the duct. It will be used on smaller duct heaters only when specified. The application and rating is identical to the disc type described above. This cutout is a "fail safe" type control. For pricing of the capillary type limit control see Pricing. (b) Secondary over-temperature protection (backup system) The edition of the NEC states in section (second paragraph): "In addition" (to the automatic primary limit controls) "an integral, independent, supplementary control, or controllers, shall be provided in each duct heater which will disconnect a sufficient number of conductors to interrupt current flow. This device shall be manually resettable or replaceable." The secondary protection (backup system) is always set at a higher temperature (210 F) than the automatic primary limit controls, therefore it should only operate when both an over-temperature condition occurs and the primary system fails due to frozen contacts, etc. Inducto Duct Heaters are available with the following two systems, UL listed, to meet the above requirements. Secondary Temperature Limit Controls - Disc Type (Replaceable) Wired in a power circuit on single or three phase heaters to de-energize the heater stage on over-heating. Rated at 48 AMP up to 600 volt. Temperature to open 210 degrees F. (2) Back up contactors with pilot duty manual reset. Reset is wired in series with backup contactor to deenergize heater. SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE 25

26 Disc Type: This device uses a bimetal disc to sense over-temperature conditions and is mounted through the terminal compartment. It is recommended for use on heaters to be installed in ducts up to 10 feet in width. HF series heaters are designed for manual resettable disc-type cut-out (load carrying) application. Available are one-pole and two-pole manual 48 amp maximum rated to 600 volts AC. The two-pole manual resettable will accommodate 96 amp on single phase application and 48 amp on three phase application. For selection of manual resettable disc-type cutouts, refer to pricing. FIGURE 17 - Capillary Type Manual Resettable Cutout - Capillary Type: This device is the ultimate in over-temperature protection and is recommended to be used on all heaters over six feet in "W" dimension. It is required on all heaters over 10 feet "W" dimension. The temperature sensing capillary is mounted along the top inside of the element enclosure and down stream from the elements; therefore, the air flow direction must be specified when ordering this unit. Normally only one of this type cutout is used per heater. If the heater load exceeds its rated capacity then the cutout should be used for pilot duty in conjunction with backup contactors. Refer to Pricing. Backup Contactors: When a capillary Manual Resettable cut-out, described above, is to be used as the secondary protection, and is not wired in the line to directly de-energize the heater, then one must be used, wired for pilot duty, controlling backup contactors. Backup contactors are in addition to, and independent of, the primary controlling contactor or other device, and are controlled by the manual resettable cutout only. They are wired in the line to deenergize the heater when an over-temperature condition causes the manual resettable cutout to cycle off. They may be either built-in or remote. NOTE: Backup contactors must be wired so they will not cycle off and on by the thermostat. ELECTRICAL DESIGN - Page 25 When backup and controlling contactors are built-in, the stages may be grouped to a maximum of 48 amps per circuit, before being wired through the backup contactors. When the stages are small enough to allow grouping into a circuit of 48 amp maximum, fewer backup contactors are required to de-energize the heater. EXAMPLE: A three phase heater with three stages of 16 amp each will be grouped into one circuit of 48 amps on the line side of the controlling contactors and will require only two contacts (50 amp size) on the backup contactor to de-energize this heater. The above procedure (grouping) will not apply when it is specified that each stage is to be field wired to a separate supply circuit. For maximum KW per circuit (48 amp) see Table 6. NOTE: The maximum voltage allowed on the manual resettable cutouts is 480 volt on the disc type and 277 volt for the capillary type; therefore on heaters using higher line voltages, a separate voltage source for the backup control circuit must be supplied. This may be either from a built-in transformer or from a remote supply and must be specified. Both UL and the NEC require only de-energizing type contactors for backup service. For pricing of backup contactors refer to de-energizing type contactor. Refer to Pricing. FIGURE 18 - Typical Control Transformer 10 - Built-in Control Transformers: When the control voltage is different from the duct heater power voltage, a step-down 26

27 Page 26- ELECTRICAL DESIGN transformer may be built-in to supply the correct voltage thereby eliminating the task of running a separate supply to the heater for the control circuit. The transformers are UL listed and are available with primary and secondary voltages and sizes as listed (Refer to Pricing). The VA rating required for a given quantity of definite purpose type contactors is also listed along with prices. If controlling contactors are not built-in, both the primary and secondary of the transformer are wired to a terminal block for field connection as required on the job. Unless specified otherwise the primary voltage will be the same as the heater power supply. Either or both the secondary and primary can be fused when specified. If a manual resettable cutout and backup contactors are being used and the heater line voltage exceeds the voltage rating of the cutout then the control transformers should be sized to, carry both the controlling and backup contactors or a separate supply furnished for the backup control circuit. Refer to Pricing Time Delay Relays When a positive time delay is needed between the "on" cycle of consecutive stages to prevent them from coming on simultaneously a time delay relay is available built-in and factory wired. For control voltages of 24, 120, 208, 240 and 277 the 600 type is used, wired as shown in diagram E5-B. The 600 type gives approximately a 25 second delay in the "on" cycle, but is wired to turn the heat off immediately when thermostat is satisfied, however a few seconds are required for the delay relay to recycle off in order to repeat the on delay sequence. Refer to Pricing Indicator (pilot) Light: Neon lights, mounted through the front door panel of the control box can be wired to indicate when: (1) One stage is on (2) Each stage is on (3) An over-heating condition occurs. Each light is marked as to the function it indicates. For available circuitry see wiring diagram numbers E7-A, B, C, D, E, and F. The lights are mounted on the front door panel for easy viewing and are available for 120, 208/240, 277 or 480 volts. Refer to Pricing. FIGURE 20 - Application of indicator light ana pilot switch Pilot Switch: A single pole toggle switch is available, which can be factory wired to prevent operation of a heater stage or the entire heater (see diagram number E8 A & B). The pilot switch can be used in control circuits of 24, 120, 208/240 or 277 volts. Note: Both UL and NEC require that disconnecting type contactors be used when a pilot switch is used. This pilot switch does not serve as the disconnect switch as required by the NEC. Refer to Pricing. FIGURE 19 - Time Delay Relay type 24A11. Switch rating 25 amp, 250 voltage maximum. Timer draws.15 amp for anticipator setting. FIGURE 21 -Pilot Relay Rating: 8 Amp resistive; 3 Amp at 125 volt and 1.5 amp at 250 volt inductive. SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE 27

28 14 - Pilot Relay: In some cases when using a 24 volt control system the VA load of several heavy duty contactors may exceed the capacity of the thermostat or the low voltage transformer. In such cases a pilot relay can be built in, controlled by the 24 volt circuit to switch line voltage (250 volt maximum) which operates the heavy duty contactors. Refer to Pricing Section Pneumatic-Electric (P.E.) Switches: When a pneumatic-control system is used, P.E. switches are required to control the heater directly (load carrying) or to operate the controlling contactors of the duct heater (pilot duty). The P.E. switches, may be built in and factory wired. Inducto offers a number of P.E. switches that can be purchased and installed from our own stock. This application is UL approved and carries the standard one year warranty. Refer to Pricing Section. ELECTRICAL DESIGN. Page Step Controllers - Built in or remote. A - Electric Step Controllers: This built-in modulating electric step controller was developed especially for use in duct heaters and has a 150ºF ambient temperature rating. Standard time cycle for 10 switches to come on is 13 minutes. Built-in recycle relay prevents entire load from coming on at once after power failures. Switches are rated for pilot duty only (up to 240V) and must be used to control contactors. Specify holding coil voltage of 120V, 208V or 240V. For 480V line voltage applications, specify a 480V/120V transformer. Built-in transformer provides 24V for thermostat circuit only not for contactor holding coils. Minimum terminal box height is 12". Use T921A or T991A thermostat or equivalent. Should power for the step controller be furnished from the duct heater control transformer add 25VA to the required transformer capacity. NO. STEPS CATALOG NUMBER NUMBER OF STEP CONTROLLERS SUPPLIED 2-5 S984D S984F S984J+S984D S984J+S984F 2 FIGURE 22-A Typical P.E. Switch A common practice has been for the controls contractor to send the switches to the factory for wiring and mounting. This leaves only the tubing connections and adjustment to be done in the field. P.E. switches supplied by others are not covered in the Inducto warranty, but if selected from the following list the heater will bear the UL label. Check the factory for additional listing. Perm Controls Model 6270, 6272, P10-BC,-BH,-FC, P67-AA, -CA, -EA, -FA Honeywell Model P658-A, -B, Model L404-A, -B, -C, -D, -F, P643A, P654A. L604A Robertshaw Model R423, R422, R424 Powers Model , , -2, -4, -5, -6, 251 Johnson Service Model G-270, -271, P7100, P7200, Mercoid Model AP , -26, -36, Barber Coleman Model PC-126,-127,-131,-132,-111,-141,-151 See wiring diagrams Figure E-6 for Pilot Duty and E-27 for load carrying systems. Refer to Pricing Section. B - Thermostats FIGURE 23 - Electric Step Controller Suggested for use with above electric step controllers. ROOM TYPE T921A (Modulating) FIGURE 24 Catalog Number Range Voltage Throttling Range T921A 56-84ºF. 24V V½ºF. Only Type Room 28

29 Page 28- ELECTRICAL DESIGN Catalog Number Range Voltage Throttling Range T991A F. 24V 2½ F. Only Furnished w/ 4½" bulb + 60" capillary tubing Type Duct C - Pneumatic Step Controller: These step controllers are used for sequence control of electric duct heaters and other devices. The basic unit consists of a series of switches, cam operated by a common drive shaft, driven by a pneumatic actuator, all mounted on a common base. The switches are enclosed with a metal cover. An external pointer indicates the shaft position thru 180 from full "on" to full "off". Switches are factory set for normal operation and cams can easily be field adjusted. Switch differential is fixed with 5 angular degrees minimum. The switch rating is 20 amperes at 120, 250 and 480 volts AC, 1 HP at 125V and 2 HP at 250V. The power required for the SP-300 series or equivalent is 0-15 PSI air supply. Typical pneumatic thermostats are available to operate this controller. For pricing see Pricing Section. Check the factory for additional listing. FIGURE 26 Pneumatic Step Controller Electronic Step Controller 100% Solid State Operation Operation typical of temperature regulation is as follows: Heating: As the temperature drops below the setpoint, the first stage heating circuit is energized. If the temperature continues to drop, the second, and subsequent, heating circuit(s) will be engaged. When the temperature rises above the "pull-in point" for a stage, that stage drops out. Time delay between stages assures sequencing of stages, in order, regardless of demand requirements. Sequencer re-programs to start (deadband) on power failure. Features Solid State circuitry. Printed circuit wiring Automatic changeover between mode function (heating and cooling) Time delay between stages assures sequencing of steps, regardless of demand. Re-programs to start through first stage on power failure. Thermistor sensing or ohm input. Wall thermostat may be horizontally or vertically mounted. Senor may be wall mounted, or remote mounted. Remoted setpoint and/or sensor location available. Setpoints and deadband field adjustable. Unlimited selection of differential between stages and deadband range features. SPECIFICATIONS/ELECTRICAL Input Voltage VAC Current (Logic) 150 MA Current (Load) 1 Amp/Stage Output Voltage Same as input Current 1 Amp/Stage Range of Setpoint 20 F Range Limits 0 to125 F THERMISTOR INPUT Adjustment/Settings Factory Min. Max. Deadband 2 F 1 F 15 F Pull-in between stages 1.5 F 0.5 F 6 F+ Hysteresis (pull-in/ drop out) 1.0 F Not field adj OHM INPUT Adjustment/Settings (On Application, consult factory) Operating Temperature - 15 F to 140 F Input Signal Standard 10K Optional ("A" suffix) ohm SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE 29

30 - CONTROL THERMOSTATS - ELECTRICAL DESIGN. Page 29 CATALOG NUMBER TYPE TEMP. RANGE VOLTAGE AMPERE RATING STAGES NO. ACTION FEATURES 1A22 Room 50-90ºF V HT. Bimetallic TJT-120 Room 60-90ºP 24V. 1 HT. Bimetallic 1F Room 45-90ºF 25V 1 HT. Mercury IF Room 45-90ºF 25V 1 HT. Mercury 1C71-51 Room HT-50-85ºF CL55-90ºF 25V 2HT. 1CL. Mercury Load Carrying Snap Action Adj. Anticipator 0.3 to 1.0 A. Adj. Anticipator 0.15 to 1.0 A. ½º Differential HTG.Adj.: 0.15 to 1.0A. Cooling: 0 to 1.5 A. HTG. Adj.: 0.15 to 1.0A. Cool Fixed: 0 to 1.5 A. 1C Room 50-85ºF 25V 2HT. Mercury Adjustable 0.15 to 1.0A T675A T675A Duct ºF V Outdoor Bulb M7M Room 35-90ºF M7M-TP Room 35-90ºF M7-TP Room 35-90ºF TC-282 Remote Bulb L6018D-1004 Remote Bulb 0-100ºF V V V V 10-90ºF V 55-85º F Ditto 8 A.@ 120V 5.1 A.@ 240V 8A@ 120V V 22A@ V 18A@277V 1 HT. Hydraulic 1 HT. Hydraulic 2HT. Bimetallic Ditto 2HT. Bimetallic Ditto 1 HT. Bimetallic 12A@ 120V 6 240V 1600VA 120V V 1600 VA 3 SPDT Hydraulic 2 SPDT Hydraulic 5' Copper Capillary ½ x3-9/16 Bulb Adj. Diff.: 3.6 to 12ºF 20' Copper Capillary ½ x 4-3/16 Bulb Adj.Diff.: 3 to 10ºF ½ºF Diff. 1½º Bet. Switches ½ºF Diff. 1½ º Bet. Switches Tamper Proof ½ºF.Diff. 4 to 6 cycles/hour. Tamper Proof Adj.Diff. 2-7ºF. Bet. Stages 0-20ºF 6' Cap. Lockable Knob Stage Diff. 2ºF. Interstage Diff. 4½ºF,5½' Cap. T42H-1081 Room 40-80ºF Ditto 1 A 240V 2 HTG. Mercury Stage Diff. 1ºF.Interstage Diff. 1-5ºF V T42M-1031 Room 40-80ºF Ditto Ditto 3 HTG. Hydraulic Stage Diff 2ºF,Interstage Diff. 2ºF. 1A22 TJT-120 1F T675A-1540 T675A-1565 L6018D F C C M7M M7M-TP M7-TP TC-282 T42M T42H

31 Page 30 - ELECTRICAL DESIGN E - REMOTE CONTROL PANELS In some applications the required components cannot be built in the duct heater terminal box because of space limitations, inaccessibility, etc. In this case some, or all, of the components can be mounted and factory wired internally, as applicable, in a panel for remote mounting. All terminals are marked to clearly indicate the field connections between the panel and the heater. The panel is of the same construction as the heater terminal box and the same components will be used as previously described in this catalogue for use in the Raywall duct heater. The required controls are controlling contactors, overcurrent protection, back up contactors (if used as the required backup system), and all must be supplied by the heater mfg. as required by UL and NCC. Heater and panel will be completely coordinated, ie: circuit sizing, terminal markings, etc., and a wiring diagram provided showing inter connections between components. The panel will be UL listed with the same controls and combinations as the heater with integral controls. Components that may be installed in remote panels are as follows: Controlling contactors Backup contactors Transformers SCR units Fusing or circuit breakers P.E. switches Disconnect switches Pilot lights Pilot switches Step controllers, program switches SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE FIGURE 27 A Typical Remote Panel

32 A depend upon the INDUCTO/MARKEL INDUCTO HEATERS FORM #C91181 MARKEL PRODUCTS COMPANY JOHNSON CITY, TENNESSEE AGENT PROJECT CUSTOMER INDUCTO DUCT HEATER SUBMITTAL Page 31 OPEN COIL ARCHITECT ENGINEER CONTRACTOR COPYRIGHT 1983 INDUCTO/MARKEL PRODUCS CO. EEF 32 Item Heater Tag Qty. Model No. * * 'E' DIM. IS STANDARD 4½ " or 6 ½" MAX. or 9½" MAX. FOR DISCONNECT SWITCHES Total Kw POWER Volts Phase Control Circ. Volts No. Of Stages KW Per Circ. Healer Type Duct Size *Heatd Direction Of Air Flow Insert Flange W H M The following information is required: Quantity, KW, voltage, phase, number of circuits, controls and control volts, metal to metal duct size. CHECK AS REQUIRED: INTEGRAL BOTTOM INSERT CONTROL BOX REMOTE CONTROL ENCLOSURE (Installed only when specified) De-energizing Contactor Fusing NOTES: Disconnecting Contactor Fusing Dual Element Mercury Contactor Circuit Breaker Electric Step Controller Fused Disconnect Switch Pneumatic Setp Controller Unfused Disconnect Switch SCR Controller Dust Proof Enclosure 80/20 'A' Elements P.E. Switch Transformer w/pri. Fusing Derated Elements Protective Screen Transformer w/pri. & sec. Fusing Time Delay Differential Pressure Switch Cover Interlock Switch Fan Interlock Relay Approved Pilot Lights Replaceable Over Temperature Protection Disc Type Pilot Switch Approved as noted Capillary Manual Reset Internal Duct Insulation inch Not approved Capillary Automatic Reset Aluminized C B 1. M, B, C, A. E, D, F, and G dimensions heater design and will be determined by the factory. If any of these dimensions are critical, they must be specified under "Notes". 2. All heaters are furnished standard with Disc Type High Temperature Cut Outs (HTCO), Wiring and Terminal Strips. 3. Control panel extends on entering airside of element frame unless otherwise specified. 4. Advise details of duct insulation, Thickness, internal, external, etc.

33 Markel Products Company Commercial Division P.O. Box T CRS Johnson City, TN / ORDER AND PRICING FORM Page 80 P.O. DATE: PRICED BY: PAGE OF INVOICE SHIP TO P.O. NUMBER TAG JOB: TAG ITEM: QTY. TOTAL KW POWER VOLTS PHASE CONTROL VOLTS NO. OF STEPS HEATER TYPE I = INSERT F = FLANGED DUCT SIZE W x H OUTSIDE DIM. IF INTERNALLY INSULATED DUCT, DUCT LINER THICKNES = AIR FLOW DIRECTION "R" = LEFT TO RIGHT UP "L" = RIGHT TO LEFT DOWN SPECIAL INSTRUCTIONS TAG ITEM: QTY. TOTAL KW POWER VOLTS PHASE CONTROL VOLTS NO. OF STEPS HEATER TYPE I = INSERT F = FLANGED DUCT SIZE W x H OUTSIDE DIM. IF INTERNALLY INSULATED DUCT, DUCT LINER THICKNES = AIR FLOW DIRECTION "R" = LEFT TO RIGHT UP "L" = RIGHT TO LEF T DONW SPECIAL INSTRUCTIONS VOLTS PHASE = ( KW) AMPS PER STEP WATTS DENSITY = KW/FT 2 TOT.AMPS LIST HEATER BASE W + H $ MODEL ADDRESS KEY NO. = = = = CONTROL OPTION LIST KEY NO. QTY DESCRIPTION EACH 72- ( ) PRODUCT OF AIR FLOW $ = 73- ( ) CONTROL CHARACTORS_ $ = 76- ( ) CONTROL TRANSFORMER $ = 78- ( ) BRANCH CIRCUIT FUSING $ = ( ) = ( ) = ( ) = ( ) = ( ) = ( ) = HEATER LIST PRICE EA. $ LESS % X COST MULTIPLIER HEATER NET PRICE EA. $ VOLTS PHASE = ( KW) AMPS PER STEP WATTS DENSITY = KW/FT 2 TOT.AMPS LIST HEATER BASE W + H $ MODEL ADDRESS KEY NO. = = = = CONTROL OPTION LIST KEY NO. QTY DESCRIPTION EACH 72- ( ) PRODUCT OF AIR FLOW $ = 73- ( ) CONTROL CHARACTORS_ $ = 76- ( ) CONTROL TRANSFORMER $ = 78- ( ) BRANCH CIRCUIT FUSING $ = ( ) = ( ) = ( ) = ( ) = ( ) = ( ) = HEATER LIST PRICE EA. $ LESS % X COST MULTIPLIER HEATER NET PRICE EA. $ 33