York SUNLINE MagnaDRY DR180 Installation Manual page 71

127915-YIM-A-0405
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.).
The furnace may shut down on a high tem-
perature 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 supply air blower may energize
regardless of the room thermostat fan switch
position.
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-
Unitary Products Group
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.
10. If the blower motor runs with the fan switch in the
"ON" position but does not run shortly after the fur-
nace has ignited when the fan switch is in the
"AUTO" position, check the room thermostat for
contact between R and G during "W1" calls.
On calls for heating, the supply air blower operates but
the draft motor does not (the room thermostat fan
switch is in the "AUTO" position).
1. The draft motor has inherent protection. If the
motor shell is hot to the touch, wait for the internal
overload to reset.
2. 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.
3. If line voltage is not present, check for line voltage
at the heat relay (RW1) contacts in the main con-
trol box and check to see if the (RW1) is pulled in.
4. If the (RW1) relay is pulled in, check for a loose line
voltage connection.
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