Residential Air Conditioners and Heat Pumps Using R-22 and Puron® Refrigerant: Application Guideline and Service Manual
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
16
Defrost Speedup (KH32EA001/007)
To test the defrost function on these units, speed up pins are provided on
the circuit board. To force a defrost cycle, the defrost thermostat must be
closed, or the defrost thermostat pins must be jumpered. Follow the steps
below to force a defrost cycle:
1. Jumper the DFT input
2. Short the speed up pins. This speeds up the defrost timer by a factor
of 256. The longer the defrost interval setting, the longer the pins
must be shorted to speed through the timing. For example, if
interval is 90 min, the speed up will take (90/256)min x (60seconds
/minute)= 21 seconds max. This could be shor3cter depending on
how much time has elapsed since the defrost thermostat closed.
3. Remove the short immediately when the unit shifts into defrost.
Failure to remove the short immediately will result in a very short
forced defrost cycle (the 10 minute timer will be sped through in 2
seconds)
4. When defrost begins, it will continue until the defrost thermostat
opens or 10 minutes has elapsed.
NOTE:
The T1 terminal on the defrost board powers the defrost timing
function. This terminal must be energized before any defrost function
will occur.
If defrost thermostat is stuck closed:
Whether the unit is in heating or cooling mode, it will run a defrost cycle
for 10 minutes each time the compressor has been energized for the
selected time interval. The board will terminate automatically after 10
minutes of defrost time regardless of defrost thermostat position.
If defrost thermostat is stuck open:
The unit will not defrost
NOTE:
Unit will remain in defrost until defrost thermostat reopens at
approximately 65°F coil temperature at liquid line or remainder of
defrost cycle time.
5. Turn off power to outdoor unit and reconnect fan-motor lead to OF2
on control board after above forced-defrost cycle.
If unit will not defrost:
1. Perform the speedup function as described above to test the defrost
function of the circuit board.
2. If the unit does not go into defrost after performing the speed up,
check for 24 volts on the T1 terminal. This terminal powers the
defrost circuit, and must be energized before any defrost function
can occur. The T1 should be energized once the Y terminal is
energized and the pressure switches are closed. Ensure the T1 wire
is connected at the contactor, and that 24 volts is present on the T1
spade terminal.
3. If all voltages are present and unit will still not run defrost, remove
thermostat pigtail harness from board and perform checks directly
on input pins with jumper wires. The pigtail may have a bad
connection or be mis-wired.
To fully troubleshoot defrost thermostat and control function
(HK32EA001/007):
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
Evolution (¥ for open thermostat) depending on outdoor
temperature.
4. Jumper between DFT and R terminals on control board as shown in
.
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 32°F. Check resistance across defrost
thermostat leads using ohmmeter. Resistance of zero indicates
defrost thermostat is closed and operating properly.
9. Short between the speed-up terminals using a thermostat
screwdriver. This reduces the timing sequence to 1/256 of original
time. (See
.)
10. Unit is now operating in defrost mode. Check between C and W2
using voltmeter. Reading on voltmeter should indicate 24v. This
step ensures defrost relay contacts 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 2 sec to remove speed-up jumper after unit has
switched to defrost, the unit will switch back to heat mode.
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 65°F.
13. Shut off unit power and reconnect fan lead.
14. Remove jumper between DFT and R terminals. Reconnect defrost
thermostat leads. Failure to remove jumper causes unit to switch to
defrost every 30, 60, or 90 minutes and remain in defrost for full 10
minutes.
15. 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 defective thermostat as
follows:
1. Follow items 1-5 above.
2. Route sensor or probe underneath coil (or other convenient
location) using thermocouple temperature measuring device.
Attach to liquid line near defrost thermostat. Insulate for more
accurate reading.
Table 3 – Defrost Control Speed-Up Timing Sequence
PARAMETER
MINIMUM
(MINUTES)
MAXIMUM
(MINUTES)
SPEED-UP
(NOMINAL)
30-minute cycle
27
33
7 sec
60-minute cycle
56
66
14 sec
90-minute cycle
81
99
21 sec
10-minute cycle
9
11
2 sec
5-minutes
4.5
5.5
1 sec
CAUTION
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage or
improper operation.
Exercise extreme caution when shorting speed-up pins. If pins are
accidentally shorted to other terminals, damage to the control board
will occur.
