Page 23
Installation, Operation & Maintenance Manual ( IOPCKKS60220510C1)
4.
If compressor contactor 1 is not pulled in, check for 24 volts
at the coil. If 24 volts is present and compressor contactor 1
is not pulled in, replace the contactor.
5.
Failing the above, if voltage is supplied at compressor
contactor 1, and it is pulled in, and the compressor still does
not operate, replace the compressor.
6.
If 24 volts is not present at compressor contactor, check for
24 volts at the UCB terminal, C1. If 24 volts is present, check
for loose wiring between C1 and the compressor contactor
1.
7.
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
are not present at the UCB Y1 terminal, the UCB may have
faulted. Check for 24 volts at the Y1 ECON terminal. If 24 volts
is not present at Y1 “ECON”, the UCB has faulted. The UCB
should de-energize all compressors on a loss of call for the
first stage of cooling, i.e. a loss if 24 volts at the Y1 terminal.
8.
If 24 volts are 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,
threshold 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.\
9.
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 a 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, remove any call for cooling.
This will reset any compressor lock outs.
* NOTE : While the above step will reset any lock outs,
compressor # 2 will be held off for the ASCD, and compressor
# 1 may be held off for a portion of the ASCD. See the next
step.
10.
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.
11.
If 24 volts is present at the UCB Y1 terminal and the compressor
is not out due to a protective switch trip, repeat trip lock
out, or ASCD, the economizer terminals of the UCB may be
improperly wired. Check for 24 volts at the Y1 “OUT” terminal
of the UCB. If 24 volts is present, trace the wiring from Y1
“OUT” for incorrect wiring. If 24 volts is not present at the Y1
“OUT” terminal, the UCB must be replaced.
12.
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, has faulted.
13.
If none of the above correct the error, replace the UCB.
UNIT FLASH CODES
Various flash codes are utilized by the unit control board (UCB) to
aid in troubleshooting. Flash codes are distinguished by the short
on and off cycle used (approximately 200 ms on and 200 ms off).
To show normal operation, the control board flashes a 1 second
on, 1 second off heartbeat during normal operation. This is to
verify that the UCB is functioning correctly.
Do not confuse this with an error flash code. To prevent confusion,
a 1-flash, flash code is not used. Current alarms are flashed on the
UCB LED. Pressing and releasing the ALARMS button on the UCB
can check the alarm history. The UCB will cycle through the last
five (5) alarms, most recent to oldest, separating each alarm flash
code by approximately 2 seconds.
In some cases, it may be necessary to “zero” the ASCD for the
compressors in order to perform troubleshooting. To reset all
ASCDs for one cycle, press and release the UCB TEST button once.
See table 10, Unit Flash Codes.
1: These flash codes do not represent alarms
TABLE 10: UNIT FLASH CODES
