Carrier ALLEGRO 42HQE009N Service Manual page 19

9.9 Defrosting operation (Available for heating only).
9.9.1 Defrosting condition: Defrosting starts when either of the following ①&②:
① A and B are satisfied:
A: The compressor keeps running for 40 minutes or more.
B: The temperature difference of evaporator and room temperature meets one of the
following:
② Calculate from the end of latest defrost, evaporator high temp. protection only closes outdoor
fan with the compressor still running. Add up to 90 minutes.
9.9.2 Defrosting time
If the temp. difference condition ① is satisfied for less than 40 minutes, this can be regarded
as severe frosting. The defrosting time is 10 minutes.
If the temp. difference condition ② is satisfied for more than 40 minutes, the defrosting time is
6 minutes.
If the temp. difference condition ① is satisfied out of 40 minutes, generally the defrosting time
is 6 minutes, after three continuous 6-minute defrost, the fourth should be 10 minutes defrost.
The circulation is as following:
→6-minute defrost → 6-minute defrost→6-minute defrost→10-minute defrost→
9.9.3 Ending condition of defrosting
If one of following conditions is satisfied, end the defrost and turn into heating mode:
A. The defrost time has reached to 6 or 10 minutes.
B. The compressor current has reached to I
models.
9.9.4 Defrosting Actions:
Compressor
4-way Valve
Outdoor Fan
Indoor Fan
℃
Fan speed is high
Fan speed is mid
Fan speed is low
Breeze
Defrost 10or 6minutes
45S
40S
10S
Temp. of evaporator---room temp.
≤TH
≤TM
≤TL
Meet only if it is Breeze
or above, I
DEFROST
25S
23S
18
DEFROST
DEFROST
DEFROST
differs in different
DEROST