Product data

Page 21
Installation, Operation & Maintenance Manual (IOPCKKS60220510B1)
* On calls for cooling, if the compressors are operating but
the supply air blower motor does not energize after a short
delay (the room thermostat fan switch is in the “AUTO”
position).
1. Turn the thermostat fan switch to the ON position. If the
supply air blower motor does not energize, go to Step 3.
2. If the blower motor runs with the fan switch in the ON position
but will not run after the first compressor has energized
when the fan switch is in the AUTO position, check the room
thermostat for contact between R and G in the AUTO position
during calls for cooling.
3. 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 blower contactor, and that the contactor is pulled in.
Check for loose wiring between the contactor and the supply
air blower motor.
4. If blower contactor is pulled in and voltage is supplied to
contactor, lightly touch the supply air blower motor housing.
If it is hot, the motor may be off on internal protection. Cancel
any thermostat calls and set the fan switch to AUTO. Wait for
the internal overload to reset. Test again when cool.
5. If blower contactor is not pulled in, check for 24 volts at the
contactor coil. If 24 volts are present but it is not pulled in,
replace the contactor.
6. Failing the above, if there is line voltage supplied at contactor
and it is pulled in, and the supply air blower motor still does
not operate, replace the motor.
7. If 24 volts is not present at blower contactor, check that 24
volts is present at the UCB supply air blower motor terminal,
“FAN”. If 24 volts is present at the FAN, check for loose wiring
between the UCB and blower contactor.
8. If 24 volts is not present at the “FAN” terminal, check for
24 volts from the room thermostat. If 24 volts are not
present from the room thermostat, check for the following :
t 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),
t Proper wiring between the room thermostat and the UCB, and
t Loose wiring from the room thermostat to the UCB.
9. 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.
10. If the thermostat and UCB are properly wired, replace the
UCB.
On calls for cooling, the supply air blower motor is operating
but compressor # 1 is not (the room thermostat fan switch is
in the “AUTO” position).
1. If compressor # 1 does not energize on a call for cooling,
check for line voltage at the compressor contactor 1, and that
the contactor is pulled in. Check for loose wiring between the
contactor and the compressor.
2. If compressor contactor 1 is pulled in and voltage is
supplied, lightly touch the compressor housing. If it ishot, the
compressor may be off on inherent protection. Cancel any
calls for cooling and wait for the internal overload to reset.
Test again when cool.
3. If compressor contactor 1 is not pulled in, check for 24 volts
at the coil. If 24 volts are present and contactor is not pulled
in, replace the contactor.
4. Failing the above, if voltage is supplied at compressor
contactor 1, it is pulled in, and the compressor still does not
operate, replace the compressor.
5. If 24 volts is not present at compressor contactor 1, check for
24 volts at the UCB terminal, C1. If 24 volts is present, check
for loose wiring between C1 and the compressor contactor.
6. If 24 volts is not present at the C1 terminal, check for 24 volts
from the room thermostat at the UCB Y1 terminal. If 24 volts is
not present from the room thermostat, check for the following :
t 24 volts at the thermostat Y1 terminal.
t Proper wiring between the room thermostat and the
UCB, i.e. Y1 to Y1, Y2 to Y2.
t Loose wiring from the room thermostat to the UCB.
7. If 24 volts is present at the UCB Y1 terminal, the compressor
may be out due to an open high pressure switch, low pressure
switch, or freezestat. Check for 24 volts at the HPS1, LPS1,
and FS1 terminals of the UCB. If a switch has opened, there
should be a voltage potential between the UCB terminals, e.g.
if LPS1 has opened, there will be a 24 volt potential between
the LPS1 terminals.
8. If 24 volts is present at the UCB Y1 terminal and none of the
protection switches have opened, the UCB may have locked
out the compressor for repeat trips. The UCB should be
flashing an alarm code. If not, press and release the ALARMS
button on the UCB. The UCB will flash the last five alarms on
the LED. If the compressor is locked out, cancel any call for
cooling. This will reset any compressor lock outs.
NOTE : While the above step will reset any lockouts,
compressor # 1 may be held off for the ASCD. See the next
step.
9. If 24 volts is present at the UCB Y1 terminal and none of the
switches are open and the compressor is not locked out, the
UCB may have the compressor in an ASCD. Check the LED for
an indication of an ASCD cycle. The ASCD should time out
within 5 minutes. Press and release the TEST button to reset
all ASCDs.
10. If none of the above corrected the error, test the integrity of
the UCB. Disconnect the C1 terminal wire and jumper it to
the Y1 terminal. DO NOT jump the Y1 to C1 terminals. If the
compressor engages, the UCB has faulted.
11. If none of the above correct the error, replace the UCB.
* On calls for the second stage of cooling, the supply air blower
motor and compressor # 1 are operating but compressor #
2 is not (the room thermostat fan switch is in the “AUTO”
position).
1. Compressor # 2 will not energize simultaneously with
compressor #1 if a call for both stages of cooling is received.
The UCB delays compressor # 2 by 30 seconds to prevent
a power surge. If after the delay compressor # 2 does not
energize on a second stage call for cooling, check for line
voltage at the compressor contactor 2, and that the contactor
is pulled in. Check for loose wiring between the contactor and
the compressor.
2. If compressor contactor 2 is pulled in and voltage issupplied,
lightly touch the compressor housing. If it is hot, the
compressor may be off on inherent protection. Cancel any
calls for cooling and wait for the internal overload to reset.
Test again when cool.