Duct Heaters Synheat duct heaters come in various sizes and dimensions to fit any compartment. There are three types of duct heaters available: open coil, tubular element or finned tubular heating elements that are either flanged or inserted in the duct. Air duct heaters are primarily used in air flowing ventilation systems and comfort heating applications while process duct heaters are mainly used for industrial process heating applications (ovens that require re-circulated air or forced circulation). A broad range of custom built electric duct heaters with capacities up to 500kW is available upon request. Our heaters can be used for applications with the following voltages: 200-277 volts/1 phase 220-277 volts/3 phase 400-415 volts/3 phases 440-600 volts/3 phases Insert Type Duct Heater Cylindrical Type Duct Heater Flange Type Duct Heater
By design, all the heaters are made non-sensitive to air flow direction. The built-in high limit thermal cut-outs are located in such a way that the air flow could be in any direction without impairing safety and the same heater could be installed in a horizontal or vertical duct. Normally, electric heaters are not designed to be used in series in a heating installation. For very large heaters, manufacturing, shipping, field handling and installation, can be simplified by using two or more units specially designed for parallel installation. Each section has its own cut-outs and terminal blocks are provided to interconnect the controls in the field.
Installation Instructions
(Insert Type, Side Slip-In, Vertical Slip-In) Installation of the slip-in heater consists of cutting an opening in the duct approximately 1/4" larger than the height and width of the heater element section. Insert heater and fasten to the duct using sheet metal screws through the control enclosure. Use extreme caution in protecting the electrical components, as metal chips lodged in the components can cause failure. Remove any metal chips that may be located in the electrical enclosure before connecting power. NOTE: To prevent element section from moving inside duct, angle clips, brackets, or blank offs should be attached to frame. Flange Type Duct Heater Installation
Flanged heaters are designed with the flanges turned out. Installation of the side flanged heater consists of inserting the flanged duct heater section into the duct and bolting in place. Cylindrical Duct Heater Installation of the round duct heater consists of attaching round duct to the inlet and outlet collars and bolting in place. Seal connection and duct joint. Install the control panel in a suitable location for the specified panel type. The wiring diagrams inside the heater door and the remote control panel door show point-to-point interconnecting wiring. Wiring must be letter to letter ("a" to "a") or number to number ("1" to "1"). Labels on each door specify the (heater/panel) configuration. DO NOT deviate from this label. Panels should be mounted in sight of unit, unless an additional disconnect is located at unit. We manufacturers a complete line of electric duct heaters with various physical sizes and KW/Btu/h outputs. Models from 1KW 6 round to 20KW Single and 3-phase units Thermal cut-outs or Temperature sensor option, if no heat is needed-element is off or modulated. Typical Applications Boost air temperature for any forced air system Additional heat for cold room Temper air temperature for Air to Air Heat Exchanger Air Source Heat Pump-rids you of cold air syndrome Ground Source Heat Pump boost / backup Temperature Sensing Duct Heaters Completely programmable duct sensing electric duct heater.
Automatically senses air temperature within ductwork Regulates electric heat output based on predetermined desired temperature. Flexible temperature ranges from 40 100 degrees Power W Btu/h output CFM Voltage V Duct Size (OD) In Inches 1000 3414 Btu/h 150 120-480 8 2500 8533 Btu/h 250 120-480 10 5000 17065 Btu/h 350 120-480 10 10,000 34130 Btu/h 700 120-480 12 Power W Btu/h output CFM Voltage V Duct Size (W x H) In Inches 5000 17065 Btu/h 350 120-480 10 x 8 10,000 34130 Btu/h 700 120-480 16 x 8 15,000 51216 Btu/h 1100 120-480 18 x 8 20,000 68288 Btu/h 1300 120-480 20 x 8 Finned Tubular Heaters & Unfinned Tubular Heaters Finned Tubular Heaters The most common design Include the highest wattage/cross section duct area Energy saver Made of a stainless steel tube with a corrugated stainless steel fin wrapped around it. Maximize the heat transfer surface of the element Provide lower operating temperature Designed for low maintenance Unfinned Tubular Heaters Available for approved special orders only Increase corrosion resistance High humidity environments Corrosive chemical contaminants in the air stream Protect from electrical shock Made of stainless steel tube Can be installed close to a register or grill N/A Designed for low maintenance How to select and specify for duct heaters required. Selecting the heater for your application can be done : 1- Determine heater capacity, voltage and electrical components 2- Determine duct dimensions, air requirements and mechanical options 3- Determine method of control, then select control components Calculating KW Requirements Once the volume of airflow (CFM in cubic feet per minute) and the required temperature rise (ΔT in degrees F) through the heater are known, the required kilowatt rating (KW) of the heater can be determined from the formula:
KW = CFM x ΔT F KW = Liters/Second x ΔT C 3193 837 Where the desired heating capacity in BTU/Hr is known, the KW is determined from the following formula: KW = BTU/Hr 3412 Static Pressure Drop
Minimum Air Velocities
Airflow Uniformity In order to prevent hot spots, the air flow must be uniformly distributed across the heater area. The following figures illustrate typical heater mis-application where the airflow is not uniform. An specifies that a heater should not be installed closer than 4 feet downstream or 2 feet upstream from a fan outlet, an abrupt transition, an elbow or any other kind of obstruction in the duct. If your application is such that one of the mentioned installations cannot be avoided, We can help you by designing around it. "Means shall be provided to assure uniform and adequate airflow over the face of the heater. Heaters installed near (within 4 feet) a fan outlet, elbows, baffle plates or other obstruction in duct work may require turning vanes, pressure plates or other devices in the inlet side of the duct heater to assure an even distribution of air over the face of the heater". Our heaters can be part of large air handling units. In this case, a heater becomes a module of a bigger unit and is designed to match the other components: filter frames, fans, cooling coils, VAV boxes, etc. Flanged units can be bolted directly to adjacent sections or slip-in models are inserted into a bigger unit. Since there can be several special conditions in such big units, the heater has to be designed to accommodate them. Special features can be installed upon request: section with no heat, pressure plates to equalize air flow, buffer sections to space the heater away from other components, etc.
Clearance The heaters are for zero clearance to combustible material. This means that there is no distance restrictions between the section of the duct housing the heater and combustible material. However, space should be provided to install and service the duct heater. Please see the minimum recommended installation clearances figures bellow. Minimum recommended distance for safety and service
Heaters Components Automatic Reset Thermal Cut-Out An automatic reset, primary safety device. Removes power from elements if overheating occurs. Standard Manual Reset Thermal Cut-Out A secondary safety device which removes power to the elements if over-heating occurs. Standard when required otherwise optional Magnetic Contactor Provides power to the individual stages of the heater. Standard Magnetic Contactor Provides power to the individual stages of the heater. Standard Airflow Switch Safety component used to prevent a heater from operating if there is no airflow. Standard for ON/OFF heaters Solid State Relay (SSR) Proportionally controls the amount of power transmitted to the heating elements. Allows quiet operation and is exceptionally reliable. Standard for proportional heaters
Electronic Controller A unique control and safety component. Controls and optimizes the power transmitted to the heating elements according to the duct temperature and air flow. Standard for proportional heaters Disconnect Switch Cuts the power supply to the heater in order to safely perform installation and maintenance tasks. Standard when required by otherwise optional Fuses Protects the total load and/or the individual heater stages. Standard when required by code, otherwise optional Anti-Condensation Heaters To prevent condensation from the terminal enclosure in the humid environment. Standard when required by otherwise optional
Field Wiring Note : Prior to installing any wiring, check the unit name plate for main power voltage, control voltage and maximum over current protection. Operating a heater at other than the specified voltage and phase can result in fire or electrical hazard. All field wiring must comply with NATIONAL ELECTRIC CODE and local code requirements. A point-to-point wiring diagram is located on the inside of the control panel door. Use copper conductors only with a minimum of 75 C insulation. Tighten all wiring lugs and terminals prior to connecting power to the unit, as they may loosen during transportation. Connect the power lines to the power distribution terminals inside the control enclosure and tighten to 35 inch-pounds (.4kg meters). If a factory wired disconnect switch is installed, connect the power lines to the line side of the switch. The line block or disconnect is rated at 125% of nominal heater amperes based on 75 C wire. Mount and wire any field installed items as indicated on the factory supplied wiring diagram. When mounting field installed components, do not jumper out or rewire any factory wiring without written approval from Synheat Mfg Pte Ltd only. Violation will void warranty and listing. Energize unit and check all controls for proper operation. Do not operate unit without proper airflow. Electric Heater Preventative Maintenance Checks & Service Schedule Caution! Disconnect All Power Sources Before Attempting To Service Or Clean Heater Before, and at Midpoint of the Heating Season: Check all electrical connections for tightness and broken terminations. Check all wiring for deterioration or over heating. Check unit for dirt or dust, and wipe clean (except elements). Check the element section for obstructions and debris. Check all components for wear and physical damage. Check all safety devices for proper operation. Check temperature controls for proper operation. Caution: In the event of thermal protection failure, it is recommended that a qualified service person investigate the cause of failure prior to returning the heater to normal service. Trouble Shooting Check installation instructions and wiring diagrams to ensure heater is wired and installed properly.
Common Symptoms Possible Cause Remedy Heater does not operate No Power Check Disconnect No Control Voltage Check Control Signal (i.e.24 volt) Check Transformer and Transformer Fusing (If Applicable), Replace it if Necessary Blown Fuse Replace Fuse Low or High Temperature Rise Short Cycling Heater W/SSR Does Not Operate Open Limited (Primary or Secondary) Airflow Incorrect Direction Low Airflow Static Pressure Damaged Elements Incompatible Thermostat or Controller Problems with Additional Stages Incorrect CFM Improper Airflow Low CFM Incorrect Signal Applied Interface Board Fuse Blown Replace Limits or Reset As Applicable Check For Continuity Access Limit to Determine if Open, Replace As Necessary Check Sensing Tube, Rotate if Needed Increase Airflow Check For Open or Damaged Elements & Replace As Necessary Check Wiring Check Compatibility Check Location of Thermostat; May be Installed in a Too Hot or Too Cold Location Check Contactors with Open Coil Check For Damaged Elements Check For Block Duct or Location of Heater Check For Even Airflow Across The Face of Element Section Check For Blocked Duct Check For Dirty Filters Check Remedies For Improper Airflow Check Air Velocity Verify Signal Input Replace Fuse
Safety Consideration The equipment covered by this manual is designed for safe and reliable operation when installed and operated within its design specification limits. To avoid personal injury or damage to equipment or property while installing or operating this equipment, it is essential that qualified, experienced personnel perform these functions using good judgement and safe practices. See the following cautionary statements. Danger Electrical Shock Hazards. All power must be disconnected prior to installation and serving this equipment. More than one source of power may be present. Disconnect all power sources to avoid electrocution or shock injuries. Hot Parts Hazard. Electric Resistance heating elements must be disconnected prior to servicing. Electric Heaters may start automatically, disconnect all power and control circuits prior to servicing to avoid burns. Warning Check that the unit assembly and component weights can be safely supported by rigging and lifting equipment. All assemblies must be adequately secured during lifting and rigging by temporary supports and restraints until equipment is permanently fastened and set in its final location. All unit temporary and permanent supports must be capable of safely supporting the equipment's weight and any additional live or dead loads that may be encountered. All supports must be designed to meet applicable local codes and ordinances. All fastening devices must be designed to mechanically lock the assembly in place without the capability of loosening or breaking away due to system operation and vibration.