L74A,C; L748A,C,L Oil Electronic Aquastat Controllers APPLICAION he L74A,C and L748A,C,L Oil Electronic Aquastat Controllers provide electronic temperature sensing in a UL limit-rated control with a single sensing probe. he L74A,C and L748A,C,L control the circulator, oil burner and boiler temperature. he L74A,C and L748A,C,L replace the L84A, L84C, L74A,C, L748A and L848A Controllers. he L74A,C and L748A,C,L series of controls provide status and diagnostic information through an LED display. hese Aquastat Controllers are intended for use in residential-type applications. SPECIFICAIONS Electrical Ratings: Voltage: 0 Vac, 60 Hz. Power: 7 VA maximum at 0 Vac plus external loads. hermostat current: 00 ma nominal at 4 Vac. Burner Relay: 7.4 A at 0 Vac Full Load Amperage (FLA); 44.4 A inrush Locked Rotor Amperage (LRA); Less Ignition Load: 60 VA. Circulator Relay: 7.4 A at 0 Vac FLA; 44.4 A inrush LRA. Zone Controller (): 7.4 A at 0 Vac FLA; 44.4 A inrush LRA. NOE: All loads combined cannot exceed 000 VA. Environmental Ratings: emperature: -0 F to +50 F (-4 C to +66 C). Humidity: 0 to 95% relative humidity, noncondensing. Approvals: Underwriters Laboratories Inc. Component Recognized. Canadian Underwriters Laboratories Inc. Component Recognized. INSALLAION INSRUCIONS Accessories: Sensor (See able ). 4,000,485-06 /4 in. (6.5 mm) diameter, -/4 in. (.75 mm) long glass cartridge Fuse, A, Slow-Blow. 0650 Heat Conductive Compound. 7AA Sensor Well Clamp. able. Wells for L74A,C; L748A,C,L Controllers. Part Number Spud Size in. (mm) able. Sensors for L74A,C and L748A,C,L Controllers. INSALLAION Insertion in. (mm) Insulation in. (mm) 869A / (.7) NP (76.) -/ (8.) 870A /4 (9.05) NP (76.) -/ (8.) Part Number Length in. (mm) Application 5000464-00 (04.8) Well-mounted controls 5000464-00 8 (457.) Flush-mounted controls 5000464-00 4 (609.6) 5000464-004 6 (94.4) 5000464-005 48 (9.) When Installing this Product.... Read these instructions carefully. Failure to follow them could damage the product or cause a hazardous condition.. Check the ratings given in the instructions and on the product to make sure the product is suitable for your application.. he installer must be a trained, experienced service technician. 4. After installation is complete, check out product operation as provided in these instructions. 5. Set High Limit, Low Limit and Low Limit Differential to the settings recommended by the boiler OEM. 6. Record the maximum High Limit setting from the replaced controller in the text box provided on the cover insert label. 7. Record the High Limit setting at time of installation in the text box provided on the cover insert label. 68-08-0
L74A,C; L748A,C,L OIL ELECRONIC AQUASA CONROLLERS WARNING Electrical Shock Hazard. Can cause severe injury, death or property damage. Disconnect power supply before beginning installation to prevent electrical shock or equipment damage. Mounting he L74A,C and L748A,C,L models are available in a well-mount, horizontal position, vertical position, or flush mounted remote from the well versions. Dimensions for the variety of mounting options are shown in Fig.. Note that each identity will have only a single mounting option. /4 (75) 7-/8 (8) 6-/ (66) 5-/6 (45) -/ (77) /8 (0) -/6 (0) -/8 (9) -5/8 (67) 4-/4 (09) -/ (86) x /4 (7) x /8 (9) /6 () -/6 (5) M47B Fig.. L74A,C; L748A,C,L mounting dimensions in inches (mm). IMPORAN Immersion well must fit sensing element and sensor must rest against bottom of well. New Installation Order well assemblies separately; see able and form no. 68-0040, Immersion Wells and Compression Fittings for emperature Controllers. Boilers usually have tappings that allow the well to be mounted horizontally so boiler water of average temperature can circulate freely over the well.. urn off all power and drain the boiler.. If no tapping is provided, prepare properly sized and threaded tapping near the top of the boiler.. Sparingly coat the well threads with pipe dope. NOE: Do not attempt to tighten by using the case as a handle. 4. Install the well in the boiler tapping and tighten securely. 5. Refill boiler and check for water leakage. 6. Loosen but do not remove the well clamp screw. 7. Fit the case into the well so the clamp on the case slides over the flange on the well. 8. Securely tighten the clamp screw. 9. Insert the sensor element into the well until it bottoms. See Replacement Sensor Installation section for details. (If necessary, slightly bend the wire inside the case to hold the sensor against the bottom of the well.) 0. urn power ON.. Set High Limit, Low Limit and Low Limit Differential to the settings recommended by the boiler OEM. (See OPERAION section.) (See INSALLAION steps 6 and 7.). On L748L models, adjust ELL option to match your configuration (see OPERAION section, and Fig. and ). IMPORAN Best thermal response is obtained with a well that snugly fits the sensor. Insert the sensor until it rests against the bottom of the well. Use a well of correct length and bend the wiring, if necessary, to hold the bulb against the bottom of the well. If the well is not a snug fit on the sensor, use the heat-conductive compound (furnished with RADE models) as follows: Fold the plastic bag of compound lengthwise and twist it gently. hen snip off end of bag and work the open end of the bag all the way into the well. Slowly pull out the bag while squeezing it firmly to distribute compound evenly in the well. Bend the wiring, if necessary, to hold the sensor against the bottom of the well and to hold outer end of the sensor in firm contact with the side of the well. See Fig.. Wipe excess compound from the outer end of the well. 68-08 0
L74A,C; L748A,C,L OIL ELECRONIC AQUASA CONROLLERS WIRES CONROLLER CASE WIRES BOILER BOILER IMMERSION WELL IMMERSION WELL HEA-CONDUCIVE COMPOUND (OPIONAL) HEA-CONDUCIVE COMPOUND (OPIONAL) IMMERSION WELL CLAMP IMMERSION WELL CLAMP SCREW M60 Fig. 4. Replacement sensor installation. M06 Fig.. Position of sensor in immersion well. Flush-Mounted Aquastat Replacement urn off all power and remove the old control. Refer to the cover insert of the old control to identify and tag each external lead as it is disconnected. If the old well is unsuitable for the new installation, remove it and replace it with a suitable new well. If the old well is suitable, use it. Well-Mounted Aquastat Replacement urn off all power and remove the old control. Refer to the cover insert of the old control to identify and tag each external lead as it is disconnected. If the old well is unsuitable for the new installation, remove it and proceed with instructions for new installation. If the old well is suitable, use it.. Loosen, but do not remove, the well clamp screw on the side of the control case.. Position immersion well clamp snugly over the flange of the adapter and tighten the clamp screw.. Insert the sensor into the well as shown in Fig. or. (See Replacement Sensor Installation section for details.) Replacement Sensor Installation urn off all power and:. Carefully disconnect sensor from circuit board by pulling gently on the connector.. Gently pull sensor from thermo well and through circuit board by pulling on leadwires.. Carefully align replacement sensor with hole in circuit board and guide through Aquastat case and into well. (See Fig. 5). 4. Make sure sensor is fully seated to bottom of well (See Fig. 4). Use a small pencil to measure depth of sensor in well, if necessary. 5. Connect sensor to circuit board by pressing connector on sensor unit into mating connector on circuit board (See Fig. 5). 6. For remote sensors (flush-mounted Aquastat Controllers) be sure to use 57AA Clamp (see Accessories) to securely hold sensor in place. HERMOSA ERMINALS ENVIRACOM M ERMINALS HOLES CONNECOR ENVIRACOM M ERMINALS DISPLAY L L C B C B L L C CAPACIOR CONNECOR S B C B RANSFORMER HOLES FUSE M07A FUSE RANSFORMER CAPACIOR DISPLAY HERMOSA ERMINALS M087 Fig. 5. Circuit board, showing sensor connection and well holes for vertical mount models. Fig.. Circuit board, showing sensor connection and well holes for horizontal mount models. 68-08 0
L74A,C; L748A,C,L OIL ELECRONIC AQUASA CONROLLERS WIRING WARNING Electrical Shock Hazard. Can cause serious injury or death. Disconnect power supply before making wiring connections to prevent electrical shock or equipment damage. All wiring must comply with local electrical codes and ordinances. Do not exceed the specifications in the Application section when wiring this control. Use wire rated for 94 F (90 C) or higher. IMPORAN he terminals on these Aquastat Controllers are approved for use with copper wire only. Follow the appropriate wiring diagrams shown on the inside of the front cover of the L74A,C; L748A,C,L or in Fig. 8. OPERAION General he L74A,C and L748A,C,L Oil Electronic Aquastat Controllers are primary safety limit-rated devices designed for use with oil fired boilers with line voltage burners and circulators. Many boilers do not include wiring or control compartments as part of the design, but are provided with an integral, replaceable, immersion well that is the mounting hardware for the Aquastat Controllers. Wiring to the other controls is done through flexible metal conduit. For boilers that do include a remotely (flush) mounted control, the wiring may be completed with conduit or routed behind the boiler sheet metal. A separate electromechanical high-limit is not required in a system that uses this control to meet Underwriters Laboratories Inc. requirements for oil-fired boiler assemblies, UL 76. On the L74 models, the High Limit, Low Limit, and Low Limit Differential can be adjusted to the setting recommended by the boiler OEM. On the L748 models, the High Limit is adjustable, see the Adjusting Settings section. he overall range of the High Limit is from 0 F to 40 F (54 C to 6 C). Select devices may have different ranges. Some models have limited ranges on the High Limit setpoint; this limited range is listed on the device label. Some models also have a Low Limit and Low Limit Differential adjustment. he range of the Low Limit is from 0 F to 0 F (4 C to 04 C). Select devices may have different ranges. he L74A,C and L748A,C,L are designed for use with 4 Vac electronic and electromechanical thermostats and EnviraCOM enabled thermostats, and have screw-type terminals for easy field connection. Adjusting Settings o discourage unauthorized changing of Aquastat settings, a procedure to enter the ADJUSMEN mode is required. o enter the ADJUSMEN mode, press the UP, DOWN, and I buttons (Refer to Fig. 5) simultaneously for three seconds. Press the I button until the feature requiring adjustment is displayed: HL_ High Limit. LL_ Low Limit (L74 only). Ldf Low Limit Differential (L74 only). F C. ELL External Low Limit (L748L only) hen press the UP and/or DOWN buttons to move the set point to the desired value, to change between F and C, or to enable (On) or disable (Off) the External Low Limit. After 60 seconds without any button inputs, the control will automatically return to the RUN mode. Display In the RUN mode, the Aquastat will flash bt (boiler temp) followed by the temperature (i.e., 0), followed by F or C. o read boiler settings, press the I key to read the parameter of interest. For example, press I and High Limit (HL) is displayed, followed by a three-digit number, i.e., 0, followed by F or C. Pressing the I button again (on L74 models) will display the Low Limit (LL) followed by a three-digit number and the corresponding degree designator. See Display Readout, Fig. 6. After approximately 60 seconds without any key presses, the display will enter a dim display mode. o return to the bright display mode, simply press any key. Display Shows Description Boiler emperature High Limit Low Limit (L74 only) Low Limit Differential (L74 only) External Low Limit Enabled (L748L only) Local hermostat Status Enviracom hermostat Status Code Degrees Fahrenheit Degrees Celsius Fig. 6. Display readout definitions. M870 68-08 0 4
L74A,C; L748A,C,L OIL ELECRONIC AQUASA CONROLLERS Operation he L74 and L748 models can be in any of four operational states: Normal, High Limit, Low Limit and. he controller moves back and forth from High Limit to Normal to Low Limit state as part of normal operation. Only devices having High Limit settings are restricted to the High Limit and Normal states. However, the controller will enter the state when there is an abnormal condition. he operating states are:. Normal: Boiler temperature went below the High Limit setting (minus the Differential) and has not exceeded the High Limit setting; or, the boiler temperature went above the Low Limit setting and has not gone below the Low Limit setting (minus the Differential); or, input is not powered with 0 Vac (only L748L with ELL set On).. High Limit: Boiler temperature went above the High Limit setting and has not dropped below the High Limit setting (minus the Differential).. Low Limit: Boiler temperature went below the Low Limit setting (minus the Low Limit Differential) and has not gone above the Low Limit setting; or, input is powered with 0 Vac (only L748L with ELL set On). 4. : he controller has detected an error condition (e.g., open sensor) and has shut down the burner output. he output is energized. he controller continues to monitor the system and automatically restarts if the error condition clears. Refer toable 4. he operating sequence for the L74/L748 is shown in able. High Limit Controller he High Limit opens and turns off the burner when the water temperature reaches the setpoint. he High Limit automatically resets after the water temperature drops past the setpoint and through the Differential. he L748 models have High Limit Differential presets of 5 F (8 C). he L74 models have High Limit Differential presets of 0 F (6 C). Low Limit and Circulator Controller On a temperature rise, with the adjustable Differential at the default setting of 0 F (6 C), the burner circuit breaks and the circulator circuit makes (assuming no call for heat is present) at the Low Limit setpoint. On a temperature drop of 0 F (6 C) below the Low Limit setpoint, the burner circuit makes and the circulator circuit breaks. See Fig. 7. HIGH LIMI SEING LOW LIMI SEING CHECKOU L74: 0 F (6 C) DIFFERENCE L748: 5 F (8 C) DIFFERENCE 0ºF (6ºC) DIFFERENCE Fig. 7. Setpoints and differentials. Put the system into operation and observe at least one complete cycle to make sure that the controller operates properly. See ROUBLESHOOING section to use LED to assist in determining system operation. ROUBLESHOOING SWICH BREAKS ON EMPERAURE RISE. BURNER URNS OFF. CIRCULAOR OPERAES ON A CALL FOR HEA. SWICH MAKES ON EMPERAURE FALL. BURNER OPERAES ON A CALL FOR HEA. WIH NO HEAING DEMAND, SWICH BREAKS ON EMPERAURE RISE. SWICH MAKES ON EMPERAURE FALL, BURNER IS ON O MAINAIN MINIMUM WAER EMPERAURE. CIRCULAOR IS OFF. WHEN WAER REACHES LOW LIMI SEING, HE BURNER SHUS OFF OR HE CIRCULAOR PUMP SARS (WHEN CALLING FOR HEA). M64 When attempting to diagnose system performance, reference to the LED display can help to identify specific areas not working properly. he LED display will scroll Err, followed by a digit (-8). Refer toable 4 for a description of each error and suggested actions. L (HO) L CIRCULAOR L L C B OIL BURNER C B M08A Fig. 8. L74A,C; L748A,C,L single zone connections. 5 68-08 0
L74A,C; L748A,C,L OIL ELECRONIC AQUASA CONROLLERS Action hermostat calls for heat. able. L74/L748 Controller Operating Sequence. System Response Circulator starts when water temperature is above Low Limit setting (if applicable). Boiler temperature is checked. Burner starts when water temperature is below High Limit setting. Boiler Burner is turned off. Burner restarts when exceeds the the water temperature drops below the High High Limit. Limit setting minus the Differential. hermostat Circulator and burner turn off. is satisfied. condition -5. condition 6. condition 7. condition 8. If an error condition is detected, all outputs except are shut down. Burner is off. Control continues to function and restarts when error is corrected. During the error check sequence, the system checks for drift in the sensor and corrosion in the connections. EnviraCOM communication is not available. he control has reset the High Limit, Low Limit and Differential setting to a default setting and will continue to run at those settings. Performance of the system will be degraded. If the error condition is detected, all outputs except are shut down. Burner is off. Control continues to function and restarts when all three user keys have been pressed longer than 60 seconds. Code Err Err Err Err4 Err5 Err6 Err7 Err8 able 4. LED Codes. Cause/Action Sensor fault; check sensor. ECOM fault; check EnviraCOM wiring. Hardware fault; replace control. B fault; check B wiring/voltage. Low Line; Check L-L, 0 Vac. Fuse; Check ECOM wires, replace fuse. EEPROM, HL, LL, Hdf, Ldf; reset to default values. Restore desired settings. Repeated B fault (no voltage present at B when output is turned on or water temperature above 60F when voltage present at B); check B wiring/voltage. able 5. roubleshooting Guide System Condition Boiler is cold, house is cold. Boiler is hot, house is cold. Diagnostic Condition Check Action Display is OFF. 0 Vac System power. urn system power on. Display is ON. 4 Vac - No 4 V; replace control. 4 V present; disconnect Boiler starts, check wiring and thermostat. thermostat, short -. 0 Vac at B-B If no, replace control. If yes, check burner and wiring. Refer to Err on display. Display is ON. 0 Vac at C-C 0 Vac at C-C, check wiring to pump. Wiring OK, is pump running? If not, replace the pump. If pump is running, check for trapped air or closed zone valves. Boiler below the Low Limit temperature, wait for boiler to go above Low Limit temperature. Boiler above LL? If yes, check for 0 Vac between and L. If no 0 Vac, replace control. If yes, check zone relays, circulators and wiring. ELL setting (L748L only) Set ELL to Off for multizone system (see Fig. ). Set ELL to On for External Low Limit (see Fig. ). Boiler above LL? If yes, check 0 Vac at -L (only L748L with ELL set On) If no 0 Vac, check C-C (see above). If yes, check the External Low Limit control. 68-08 0 6
L74A,C; L748A,C,L OIL ELECRONIC AQUASA CONROLLERS ZONE CIRCULAOR O ADDIIONAL R845A S FOR OHER ZONES L L (HO) L74 LOW HERMOSA R845A ZONE 6 5 4 ZONE LOW HERMOSA POWER SUPPLY. PROVIDE DISCONNEC MEANS AND OVERLOAD PROECION AS REQUIRED. CONROL CASE MUS BE CONNECED O EARH GROUND. USE GROUNDING SCREW PROVIDED. CIRCULAOR OIL BURNER L L C B C B M75 Fig. 9. L74A,C multizone system with circulator connections. 865L R784 LIMI L L (HO) L L74 L 5 ENVIRACOM ERMINAL BURNER MOOR BURNER MOOR IGNIOR IGNIOR VALVE VALVE 4 CIRCULAOR L L C O REMOE ALARM CIRCUI CAD CELL CAD CELL B C B JUNCION BOX LEGEND SCREW ERMINAL /4 IN. (6 MM) QUICK CONNEC ERMINAL SOLDERLESS WIRE CONNECION POWER SUPPLY. PROVIDE DISCONNEC MEANS AND OVERLOAD PROECION AS REQUIRED. OPIONAL FEAURE ON SELEC MODELS. 4 VALVE IS OPIONAL ON SPECIFIED MODELS. 5 ENVIRACOM ERMINAL IS ALSO HE FIRS HERMOSA ERMINAL. REFER O DEVICE LABEL FOR WIRE COLOR CODE. M74 Fig. 0. L74A,C multizone system with circulator connections and EnviraCOM thermostat. 7 68-08 0
L74A,C; L748A,C,L OIL ELECRONIC AQUASA CONROLLERS ELL=OFF ELL=ON O ADDIIONAL R845A S FOR OHER ZONES ZONE CIRCULAOR L L (HO) L (HO) L R845A ZONE 6 5 R W B L6006 LOW LIMI CONROLLER L748L LOW HERMOSA 4 ZONE LOW HERMOSA L748L LOW HERMOSA CIRCULAOR OIL BURNER L L C B C B CIRCULAOR L L C POWER SUPPLY. PROVIDE DISCONNEC MEANS AND OVERLOAD PROECION AS REQUIRED. CONROL CASE MUS BE CONNECED O EARH GROUND. USE GROUNDING SCREW PROVIDED. M7 OIL BURNER B C B Fig.. L748L External Low Limit connections. POWER SUPPLY. PROVIDE DISCONNEC MEANS AND OVERLOAD PROECION AS REQUIRED. CONROL CASE MUS BE CONNECED O EARH GROUND. USE GROUNDING SCREW PROVIDED. M7 Fig.. L748L multizone system with circulator connections. Automation and Control Solutions Honeywell International Inc. Honeywell Limited-Honeywell Limitée 985 Douglas Drive North 5 Dynamic Drive Golden Valley, MN 554 oronto, Ontario MV 4Z9 customer.honeywell.com U.S. Registered rademark 007 Honeywell International Inc. 68-08 0 M.S. Rev. -07