Sunlife Enterprises SUNLINE DM180 - Manual (Page 50)

356214-XIM-A-0108
50 Johnson Controls Unitary Products
15. If none of the above correct the error, replace the
UCB.
GAS HEAT TROUBLESHOOTING GUIDE
NOTE: To find the Btu input, multiply the number of
cubic feet of gas consumed per hour by the
Btu content of the gas in your particular locality
(contact your gas company for this information
- it varies widely from city to city.).
On calls for heating, the draft motor operates and the
furnace lights but the supply air blower motor does not
energize after a short delay (the room thermostat fan
switch is in “AUTO” position).
1. Place the thermostat fan switch in the “ON” posi-
tion. If the supply air blower motor energizes, go to
Step 10.
2. If the supply air blower motor does not energize
when the fan switch is set to “ON,” check that line
voltage is being supplied to the contacts of the M3
contactor, and that the contactor is pulled in. Check
for loose wiring between the contactor and the sup-
ply air blower motor.
3. If M3 is pulled in and voltage is supplied at M3,
lightly touch the supply air blower motor housing. If
it is hot, the motor may be off on inherent protec-
tion. Cancel any thermostat calls and set the fan
switch to “AUTO”, wait for the internal overload to
reset. Test again when cool.
4. If M3 is not pulled in, check for 24 volts at the M3
coil. If 24 volts is present at M3 but M3 is not pulled
in, replace the contactor.
5. Failing the above, if there is line voltage supplied at
M3, M3 is pulled in, and the supply air blower
motor still does not operate, replace the motor.
6. If 24 volts is not present at M3, check that 24 volts
is present at the supply air blower motor terminal
on the UCB. If 24 volts is present at the UCB termi-
nal, check for loose wiring between the UCB and
M3.
7. If 24 volts is not present at the UCB supply air
blower motor terminal, check for 24 volts from the
room thermostat. If 24 volts is not present from the
room thermostat, check for the following:
a. Proper operation of the room thermostat (contact
between R and G with the fan switch in the “ON”
position and in the “AUTO” position during operation
calls).
b. Proper wiring between the room thermostat and the
UCB.
c. Loose wiring from the room thermostat to the UCB.
8. If 24 volts is present at the room thermostat but not
at the UCB, check for proper wiring between the
thermostat and the UCB, i.e. that the thermostat G
terminal is connected to the G terminal of the UCB,
and for loose wiring.
9. If the thermostat and UCB are properly wired,
replace the UCB.
Troubleshooting of components may require
opening the electrical control box with the
power connected to the unit. Use extreme
care when working with live circuits! Check
the unit nameplate for the correct line voltage
and set the voltmeter to the correct range
before making any connections with line termi-
nals.
When not necessary, shut off all electric power
to the unit prior to any of the following mainte-
nance procedures so as to prevent personal
injury.
Label all wires prior to disconnection when ser-
vicing controls. Wiring errors can cause
improper and dangerous operation, which
could cause injury to person and/or damage
unit components. Verify proper operation after
servicing.
The furnace may shut down on a high temper-
ature condition during the procedure. If this
occurs, the UCB energize the supply air blower
motor until the high temperature limit has reset.
Caution should be used at all times as the sup-
ply air blower may energize regardless of the
room thermostat fan switch position.