18
Defrost Process
You may force a defrost in heat mode by pressing the “+” and “-” buttons alternately three times within 5
seconds.
1) The unit will enter defrost when the following conditions are met:
A. Outdoor ambient <= 410 F
B. Compressor had accumulated more than 3 hours of operation in heating mode
C. The outdoor coil <= 320 F
Note: The compressor runtime will be cleared when the outdoor ambient is > 410 F or when the compressor has started
up after changing to cooling or drying mode and defrost has finished. The runtime will not be cleared when the unit has
stopped after reaching the setpoint temperature, a protection fault or changing to fan mode.
There are 3 perimeters used in the defrost algorithms, Outdoor ambient(T
outdoor
ambient), Outdoor tube(T
outdoor
tube) and
a calculated T
compensation
T
compensation
is calculated by the following:
D. After power-up, for the first defrost T
compensation
= 320 F
E. T
outdoor
tube > 360 F then T
compensation
= 320 F
F. T
outdoor
tube <= 360 F then T
compensation
= 370 F
2) When heating has operated continuously for 45 minutes, or accumulated for 90 minutes, the unit will enter defrost
mode in 3 minutes after meeting any of the conditions below:
A. Outdoor ambient >= 410 F and outdoor coil <= 280 F
B. 280 F <= T
outdoor
ambient< 410 F, “Toutdoortube -Tcompensation ≤ 21F”
C. 230 F <= T
outdoor
ambient < 280 F <= Toutdoortube -Tcompensation ≤ 18F”
D. 140 F <= T
outdoor
ambient < 230 F , T
outdoor
tube -T
compensation
<= (T
outdoor
ambient - 370 F)
E. Toutdoorambient < 140 F, Toutdoortube -Tcompensation <= (Toutdoorambient - 37 F)
3) During defrost, if run time for the compressor does not reach 3 minutes, the defrost cycle will not start for the next
2 hours. At that time the compressor stops operation and 30 seconds later the outdoor fan will stop. 30 seconds after
this the 4-way reversing valves will de-energized. Following another 30 second delay, the compressor will increase its
compressor speed for defrosting. Defrosting will last for 450 seconds or until the T
outdoor
tube >= 500 F, at this temperature
the compressor will decrease it compressor speed for 30 seconds, then will stop. In another 30 seconds the 4-way valve will
energize, the 60 seconds later the compressor and outdoor fan will start. The compressor speed for defrosting will be 85hz.
During Defrost mode, a “H1” will be displayed on the indoor front panel display indicating the user selected mode has
been overridden and the system is performing a outdoor coil defrost operation.
4) Defrost Sequence:
When a defrost condition has been met, the compressor will stop, all expansions valves will open fully, the outdoor fan will
stop 40 seconds after the compressor stops. The 4-way valve will reverse direction (cooling mode) , then the compressor
will start and enter the defrost frequency. The control, board along with ambient sensors will calculate defrost time.
5) Oil Return:
Oil return condition can be met if the unit operates at a low frequency for an extended time. The indoor display will
indicate “H1” for this condition and is a normal procedure.
Basic & Protection Functions
Basic Functions
All manuals and user guides at all-guides.com
