Lennox TPA036H4N4 Installation Instructions Manual page 33

DEFROST CONTROL (A108) CALIBRATION MODE SEQUENCE
Occurs after power up and cooling operation, or if the coil temperature exceeds
Demand defrost control defaults to 30 minute
DEMAND MODE
Accumulate compressor runtime of
more than 30 minutes while coil
temperature is below 35° F (2°C).
When the accumulated compressor
time exceeds six (6) hours or if the
coil sensor indicates frost is present
on coil, go to Defrost.
Coil temperature was above 35°F (2°C) for four (4)
minutes. of the 14−minute defrost OR reached
defrost termination temperature.
DEFROST TERMINATION
S
Compressor runtime counter RESET
S
Outdoor Fan ON
S
Reversing Valve OFF
S
W1 line OFF
Attempt to Calibration Temperature measurements are not taken for the first few minutes of each heat demand. This is
to allow coil temperatures to stabilize. demand defrost control has a maximum of 20 minutes of accumulated compressor
runtime in heat mode to calibrate demand defrost control This may involve more than one heating demand.
YES Calibration occurred
the termination temperature while in Heat Mode.
Reset Compressor Runtime / Reset Three / Five Strike Counter
THIRTY (30) MINUTE TIME /
TEMPERATURE MODE
Accumulate compressor
while coil temperature is below 35° F
(2°C). When
compressor time exceeds 30 minutes
go to Defrost.
DEFROST
S
Outdoor Fan OFF
S
Reversing Valve ON
S
W1 line ON
Monitor coil temperature and
time in defrost mode.
HOW DID DEFROST TERMINATE?
Was stable coil temperature attained
within 20 minutes?
Figure 23. Defrost Calibration
Page 33
Time / Temperature Mode
TIME/TEMPERATURE MODE
runtime Accumulate compressor runtime
while coil temperature is below 35°
the accumulated F (2°C). When the accumulated
compressor time exceeds 45
minutes go to Defrost.
Defrosted for 14−minute without the coil temperature
going above 35°F (2°C) for four (4) minutes and coil
did not reach termination temperature.
DEFROST TERMINATION
S
Compressor runtime counter RESET
S
Outdoor Fan ON
S
Reversing Valve OFF
S
W1 line OFF
NO
reverts to 45 minute time /
temperature.
45 MINUTE
Demand defrost control
TPA*H4 SERIES