66369-YIM-D-1004
Unitary Products Group
55
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 por-
tion 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 compres-
sor 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 econ-
omizer 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.
For units without economizers
: If 24 volts is present
at the Y1 “OUT” terminal, check for 24 volts at the
Y1 “ECON” terminal. If 24 volts is not present,
check for loose wiring from the Y1 “OUT” terminal
to the Mate-N-Lock plug, the jumper in the Mate-N-
Lock plug, and in the wiring from the Mate-N-Lock
plug to the Y1 “ECON” terminal.
For units with economizers
: If 24 volts is present at
the Y1 “OUT” terminal, check for 24 volts at the Y1
“ECON” terminal. If 24 volts is not present, check
for loose wiring from the Y1 “OUT” terminal to the
Mate-N-Lock plug, a poor connection between the
UCB and economizer Mate-N-Lock plugs, loose
wiring from the Mate-N-Lock plug to the
economizer, back to the Mate-N-Lock plug, and
from the Mate-N-Lock plug to the Y1 “ECON”
terminal. The economizer board may have faulted
and is not returning the 24 volts to the Y1 “ECON”
terminal even though the economizer is not
providing free cooling. To test the economizer
board, disconnect the Mate-N-Locks and jumper
between the WHITE and YELLOW wires of the
UCB’s Mate-N-Lock plug.
13. The UCB can be programmed to lock out compres-
sor operation during free cooling and in low ambi-
ent conditions. These options are not enabled by
default. They can be checked by local distributors.
14. 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.
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 9.
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.
