Carrier R-22 Application Manual And Service Manual page 19

OF2 OF1
G
E
W2
14
L
G
W3
R
R
Y
R
O
Y
C
O
30 50
W1
HK32FA003/HK32FA006
have closed, energizing supplemental heat (W2) and reversing
valve solenoid (O).
11. Unit should remain in defrost no longer than 10 minutes.
Actual time in defrost depends on how quickly speed-up
jumper is removed. If it takes 3 sec to remove speed-up
jumper after unit has switched to defrost, only 7 minutes of
defrost cycle remains.
12. After a few minutes in defrost (cooling) operation, liquid line
should be warm enough to have caused defrost-thermostat
contacts to open. Check resistance across defrost thermostat.
Ohmmeter should read infinite resistance, indicating defrost
thermostat has opened at approximately 80°F.
13. Shut off unit power and reconnect fan lead.
14. Remove jumper wire from speed-up terminal and reinsert
cover on speed-up terminals. Failure to remove jumper causes
unit to speed up operating cycles continuously.
15. Remove jumper between DFT and R terminals. Reconnect
defrost thermostat leads.
16. Replace control-box cover. Restore power to unit.
If defrost thermostat does not check out following above items or
incorrect calibration is suspected, check for a defective thermostat
as follows.
1. Follow items 1-5 above.
2. Using thermocouple temperature-measuring device, route sen-
sor or probe underneath coil (or other convenient location).
Attach to liquid line near defrost thermostat. Insulate for more
accurate reading.
3. Turn on power to outdoor unit.
4. Restart unit in heating mode.
5. Within a few minutes, liquid-line temperature drops within a
range causing defrost thermostat contacts to close. Tempera-
ture range is from 33°F to 27°F. Notice temperature at which
ohmmeter reading goes from
contacts close at this point.
6. Remove protective cover from TP1 and TP2 speed-up termi-
nals and install jumper wire on the speed-up terminals.
C
C
C
C
DFT
A88402
Fig. 19—Jumper DFT and R Terminals
to zero ohms. Thermostat
7. Unit changes over to defrost within 90 sec (depending on
timing cycle setting). Liquid-line temperature rises to range
where defrost thermostat contacts open. Temperature range is
from 75°F to 85°F. Resistance goes from zero to
contacts open.
8. If either opening or closing temperature does not fall within
above ranges or thermostat sticks in 1 position, replace
thermostat to ensure proper defrost operation.
CES0110063 DEFROST CONTROL
Some heat pumps built in 1991 and later incorporate a new defrost
control. The screw terminals found on the previous control board
have been replaced by a connector plug with stripped-wire leads.
This control board also contains the feature that allows the heat
pump to restart in defrost if the room thermostat is satisfied during
defrost. The board also contains a 5-minute cycle protector that
prevents the unit from short cycling after it cycles off or after a
power interruption. To troubleshoot the board, perform the follow-
ing items.
1. Turn thermostat to OFF. Shut off all power to outdoor unit.
2. Remove control-box cover for access to electrical components
and defrost-control board.
3. Disconnect defrost-thermostat leads from control board and
connect to ohmmeter. Thermostat leads are black, insulated
wires connected to DFT and R terminals on control board.
Resistance reading may be zero (indicating closed-defrost
thermostat), or infinity ( for open thermostat) depending on
outdoor temperature.
4. Jumper between DFT and R terminals on control board as
shown in Fig. 21.
5. Disconnect outdoor fan-motor lead from OF2. Tape lead to
prevent grounding.
6. Turn on power to outdoor unit.
7. Restart unit in heating mode, allowing frost to accumulate on
outdoor coil.
8. After a few minutes in heating mode, liquid-line temperature
at defrost thermostat should drop below closing set point of
defrost thermostat of approximately 30°F. Check resistance
19
OF2
OF1
O R T2 Y TI DFT C TEST 30 50 90
W1
O
R
W2
Y
C
CES0110063,
CES0130024
A91442
when