Carrier 48DL Installation Manual download pdf (Page 80)

264975-BIM-B-1208

80 Johnson Controls Unitary Products

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, com-

pressor #1 may be held off for 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 pres-

ent, 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.

13. 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” termi-

nal. If nothing is found, the economizer control may have

faulted and is failing to return the 24-volt “call” to the Y1

“ECON” terminal even though the economizer is not pro-

viding free cooling. To test, disconnect the Mate-N-Locks

and jumper between the WHITE and YELLOW wires of

the UCB’s Mate-N-Lock plug. If compressor #1 ener-

gizes, there is a fault in the economizer wiring or the

economizer control.

14. The UCB can be programmed to lock out compressor

operation during free cooling and in low ambient condi-

tions. These options are not enabled by default. Local

distributors can test the UCB for this programming.

For units with factory installed economizers, the UCB is

programmed to lock out compressor operation when the

LAS set point is reached.

For units without factory installed or with field installed

economizers, the UCB allows compressor operation all

the time. This programming can be checked or changed

by the local distributor.

15. 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 termi-

nals. If the compressor engages, the UCB has faulted.

16. 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” posi-

tion):

1. If installed, check the position of the economizer blades.

If the blades are open, the economizer is providing free

cooling. If the second stage of cooling is requested, fol-

lowing a short delay, compressor #1 will be energized

unless it is locked out. Typically, compressor #2 is ener-

gized only during free cooling if the call for the second

stage of cooling persists for 20 minutes.

2. 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 sec-

onds to prevent a power surge. If after the delay com-

pressor #2 does not energize on a second stage call for

cooling, check for line voltage at the compressor contac-

tor, M2, and that the contactor is pulled in. Check for

loose wiring between the contactor and the compressor.

3. If M2 is pulled in and voltage is supplied at M2, lightly

touch the compressor housing. If it is hot, the compres-

sor may be off on inherent protection. Cancel any calls

for cooling and wait for the internal overload to reset.

Test again when cool.

4. If M2 is not pulled in, check for 24 volts at the M2 coil. If

24 volts is present and M2 is not pulled in, replace the

contactor.

5. Failing the above, if voltage is supplied at M2, M2 is

pulled in, and the compressor still does not operate,

replace the compressor.

6. If 24 volts is not present at M2, check for 24 volts at the

UCB terminal, C2. If 24 volts are present, check for

loose wiring between C2 and the compressor contactor.

7. If 24 volts is not present at the C2 terminal, check for 24

volts from the room thermostat at the UCB Y2 terminal. If

24 volts is not present from the room thermostat, check

for the following:

a. 24 volts at the thermostat Y2 terminal

b. Proper wiring between the room thermostat and the

UCB, i.e. Y1 to Y1, Y2 to Y2, and

c. Loose wiring from the room thermostat to the UCB

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Carrier 48DL Installation Manual Page 80

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