035-17233-000-C-0702

1.The indoor blower motor is a non-inherently protected three-phase motor. Protection is provided by an overload relay for overcurrent and fuses for short circuit. If the motor fails to run, check the line voltage circuit and con- trol voltage circuit per the following procedure:

a.If the Indoor Blower Motor does not operate, check visually that contactor M3 is pulled in. If so, check for line voltage between all three phases at the line terminals of the Blower Overload Relay (BOR). If line voltage is found, check the leads to the blower motor for open circuit. If line voltage is found at the motor leads (inside the conduit box on the motor shell), disconnect the motor and check for open windings per the motor wiring diagram. If open wind- ings are found, replace the motor. If line voltage is not found at the BOR, trace the leads back to the field supply terminal block, checking for an open cir- cuit or blown fuses.

b.If the contactor M3 is not pulled in, check for control voltage (24V) at the M3 coil. If voltage is found, replace the contactor. If control voltage is not found at M3, check for voltage across terminals 95 & 96 of the BOR. If voltage exists, the BOR is open on over- load. The BOR should be set to the auto reset posi- tion. The BOR must cool down in order to reset. If the BOR will not reset, replace the BOR. If the BOR resets and M3 pulls in, but the indoor blower motor will still not run, refer to para. (a) for troubleshooting the line voltage supply circuit. If control voltage is not found at the BOR, trace the circuit back to the relay board and thermostat per the unit wiring dia- gram. Replace any defective components.

2.Draft motor operates and furnace lights but supply air blower does not start after a short time delay with room thermostat fan switch set to AUTO.

a.Set fan switch to ON. If blower motor runs, go to Step f. If it does not, check to see if line voltage is being supplied to the contacts of the contactor (M3), and if the contactor is pulled in. Check for loose wir- ing.

b.If contactor (M3) is pulled in, proceed with the trou- bleshooting steps indicated in Step 1 above.

c.If (M3) is pulled in and the blower motor still does not run, replace the blower motor.

d.If (M3) is not pulled in, check for 24 volts at the (M3) coil. If 24 volts is present, replace the (M3) contac- tor.

e.If 24 volts is not present at the (M3) coil, check for loose 24 volt wiring back to the relay board. Check control wiring to the room thermostat. If all is fine, replace the relay board.

f.If the blower motor runs with the fan switch in the ON position but does not run soon after the furnace

has ignited with the fan switch in the AUTO position, check for loose 24 volt wiring between the relay board in the main control box, the Mate-N-Lok con- nector in the partition between the evaporator and gas heat sections and the time delay relay (ETD).

g.If all control wiring is fine, check for 24 volts at the relay board. If 24 volts is present, replace the relay board. If 24 volts is not present, replace the (ETD) relay.

NOTE: The furnace may shut itself down on a high tempera- ture condition during the procedure, but this will not effect the test if it is done within 5 minutes of furnace shut-down.

3.The supply air blower operates but the draft motor does not when the room thermostat is set to call for heat and the fan switch in the ON position.

a.The draft motor has inherent protection. If the motor shell is hot to the touch, wait for the internal over- load to reset.

b.If the motor shell is cold with the room thermostat calling for heat, check for line voltage at the motor's Mate-N-Lok connector attached to the evaporator partition. If line voltage is present, replace the draft motor.

c.If line voltage is not present, check for line voltage at the heat relay (RW1) contacts in the main control box and check to see if the (RW1) is pulled in.

d.If the (RW1) relay is pulled in, check for a loose line voltage connection.

e.If the (RW1) relay is not pulled in, check for 24 volts at the (RW1) coil. If 24 volts is present, replace the (RW1) relay. If 24 volts is not present, check for a loose 24 volt connection back to the relay board and check the connections from the room thermostat to the relay board. If all connections are correct, replace the relay board.

4.The draft motor runs but the furnace does not light and the sparker does not spark.

a.The ignition control (IC1, IC2) may be locked out due to either a flame roll out or 100% shut off. These safety features are described above. If lock-out has occurred, 24V must be removed from the ignition controls. This is done at the unit or by resetting the room thermostat. After resetting 24V, check for proper furnace operation. If lock-out continues to occur, locate the source of the problem and correct.

b.Check all 24 volt connections from the relay board to and in the gas heat section. Check low voltage connections to the (ETD) located in the control box.

c.If the furnace is hot, it may be out on an over-tem- perature condition, wait for limit reset.

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Energy Tech Laboratories DHG180, DHG240 installation instructions 035-17233-000-C-0702
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DHG180, DHG240 specifications

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