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- 105 -
HWE09120 GB
-7- Defrost Operation Control
(1) Starting the defrost operation
The defrost cycle will start when all of the three conditions (outside temperature, cumulative compressor operation time, and
pipe temperature) under <Condition 1>, <Condition 2>, or <Condition 3> are met.
1) Pipe temperature(TH3)
The defrost cycle will not start if other outdoor units are in the defrost cycle or until a minimum of 10 minutes have passed
since the completion of the last defrost cycle.
If 10 minutes have passed since compressor startup or since the completion of a defrost cycle, a forced defrost cycle can be
started by setting DIP SW2-7 to ON.
Even if the defrost-prohibit timer is set to 90 minutes, the actual defrost-prohibit time for the next defrost cycle is 50 minutes
if the last defrost cycle took 12 minutes.
All units in the heating mode will simultaneously go into the defrost cycle in a system with multiple units. The units that are
not in operation may or may not go into the defrost cycle, depending on the cumulative operation time of their compressors.
(2) Defrost operation
Condition 1 Condition 2 Condition 3
Outside temperature
(TH7)
-5ºC [23ºF] or above -5ºC [23ºF] or below
Cumulative compressor
operation time
50 minutes or more
90 minutes or more if the defrost prohibit timer is set to 90.
250 minutes or more
Pipe temperature
(TH3)
The pipe temperature has
stayed below the temperatures
in the table below (Note1) for
three minutes.
The pipe temperature has
stayed below the value ob-
tained from the formula "Out-
side temperature (TH7) - 5ºC [
23ºF] " for three minutes, or the
63LS reading has stayed below
the value obtained from the for-
mula "1.5 + 0.02 x (20+TH7)"
for three minutes.
The pipe temperature has
stayed below the temperatures
in the table below (Note1) for
three minutes
P72 P96 P120 P144
SW3-3 OFF -10ºC -10ºC -8ºC -8ºC
SW3-3 ON -5ºC -5ºC -5ºC -5ºC
Compressor frequency Model Compressor frequency
72 model 65 Hz
96 model 65 Hz
120 model 103 Hz
144 model 103 Hz
Outdoor unit fan Stopped
SV1a ON
SV5b, SV5c OFF(open)
21S4a OFF
21S4b, 21S4c OFF
SV9 OFF
LEV1 0 pulses
*1
*1. This value may be greater than 0 pulse depending on the 63LS and TH4 status.
LEV2 3000 pulses