Trane 4WCZ6036B3000A Installation And Operation Manual page 23

Table 12. Demand Defrost Control Checkout Table (continued)
SYMPTOMS
Control does not initiate a
3.
normal defrost.
Control does not initiate a
4.
forced defrost.
Defrost initiates manually but terminates in less than 10 seconds.
5.
Defrost initiates manually but
6.
terminates on time.
Defrost initiates on
7. approximately 15/25 minute
intervals.
Defrost initiates on
8. approximately 30/45 minute
intervals.
OD fan runs during defrost.
9.
No SOV delay on defrost
10.
termination.
11. ODS-A burned out.
On SCROLL bearing units,
12.
compressor does not operate.
13. On SCROLL bearing units, no 30
second off delay at defrost
initiation.
18-BB35D1-16B-EN
CHECKS
OD Temp. below 49°F.? OD Coil temp.
1.
below 35°F.? "Delta" T increasing
2. LED flashing?
3.
Check for 24V Y-B at board with unit
running.
4. Check sensors for correct mounting
(connection) and resistance.
Short FRC_DFT pin to TEST_COMMON
5.
pin. Is defrost cycle initiated?
24V R-B & Y-B at board with unit running?
Coil sensor circuit open or reading at a
1.
very high resistance?
2. Does OD fan cycle off in defrost?
3. Windy weather preventing normal
termination?
1. Be sure OD coil is clean.
2. Coil sensor open or reading a very high
resistance?
Ambient sensor reading less than
3.
normal?
4. OD fan off in defrost?
1. TEST_COMMON pin shorted to TST pin?
2. Do both sensors check OK?
3. Verify correct system charge.
4. Verify a "forced defrost" terminates less
than 15 minutes.
5. OD fan motor off in defrost.
6. Verify proper SOV operation.
Has J1 been cut?
B to T greater than 10 volts?
1. 24V R-B at board & 24V Y-B at board?
2. Check protective devices in YO circuit.
24V YO-B present after 30 seconds.
Check voltage between control terminals 2
and 7, force a defrost cycle. Is 24V present
for 30 seconds and 0V thereafter?
YES/NO ACTIONS
Check refrigerant circuits for balanced
distribution of refrigerant if OD coil is
N
frosting and delta T is not increasing.
N Refer to SYMPTOM #1.
Complete Check #2.
Y
Repair low voltage wiring.
N
Complete Check #3.
Y
Remount or replace sensor if necessary.
Replace defrost control.
N
Y-B signal or control may be intermittent.
Y
Repair low voltage wiring.
N
Replace defrost control.
Y
Replace defrost control.
Replace coil sensor.
Y
Replace defrost control.
N
Complete Check #2.
N
Replace coil sensor.
Y
Complete Check #3.
N
Replace ambient sensor.
Y
Replace defrost control.
N
Y Remove short.
Replace defective sensor (Clear coil and re
N
gency heat light).
Complete SYMPTOM #3.
Y
Adjust as needed.
Replace defrost control.
N
See SYMPTOM #9.
Replace if necessary.
Replace defrost control.
The soft-switch time is defeated when J1 is
Y
cut.
Replace defrost control.
N
Check low voltage wiring for miswire.
Y
Check for short in low voltage wiring.
N
Repair low voltage wiring.
N
Y-B signal or control may be intermittent
N
Replace defrost control.
N
U U n n i i t t S S t t a a r r t t u u p p
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