Mitsubishi Electric PURY-P120, Service Handbook

Page: 156 / 411

[
VII
Control ]
- 147 - HWE09130 GB
-7- Defrost Operation Control
(1) Starting the defrost operation
Œ
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)
Œ
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.
Œ
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.
Œ
Even if the defrost-prohibit timer is set to 90 minutes (or 150 minutes for "Condition 3" to be met), the actual defrost-prohibit
time for the next defrost cycle is 50 minutes if the last defrost cycle took 12 minutes.
Œ
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.
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