Defrost Operation Control; Starting The Defrost Operation - Mitsubishi Electric PURY-P72 Service Handbook

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[ VII Control ]

-7- Defrost Operation Control

(1) Starting the defrost operation

ŒThe 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.
Outside temperature
(TH7)
Cumulative compressor
operation time
Pipe temperature
(TH3)
1) Pipe temperature(TH3)
SW3-3 OFF
SW3-3 ON
ŒThe 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.
ŒIf 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.
ŒEven 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.
ŒAll 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.
HWE09130
Condition 1
-5ºC [23ºF] or above
50 minutes or more
90 minutes or more if the defrost prohibit timer is set to 90.
The pipe temperature has
stayed below the temperatures
in the table below (Note1) for
three minutes.
P72
P96
-10ºC
-10ºC
-5ºC
-5ºC
- 147 -
Condition 2
-5ºC [23ºF] or below
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.
P120
-8ºC
-5ºC
Condition 3
250 minutes or more
The pipe temperature has
stayed below the temperatures
in the table below (Note1) for
three minutes
P144
-8ºC
-5ºC
GB

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