Mitsubishi Electric PUHY-M200YNW-A1 Service Handbook page 144

[5-3 Hydro Unit Control ]
(2) 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.
Outside temperature
(TH7)
Cumulative compressor
operation time
Evaporating tempera-
ture (Te)
1) Evaporating temperature (Te)
SW4 (915) OFF
SW4 (915) ON
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 SW4(913) 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.
(3) Defrost cycle
Outdoor unit fan
SV1a
21S4a
21S4b, 21S4c
SV2
SV9
SV10,SV11
*1
SV14
*1
SV15
LEV1
LEV2a
LEV2b
LEV2c
LEV4
*1. Only the EM200 through 450 models have SV14 and SV15.
*2. This value may be greater than 0 pulse depending on the 63LS and TH4 status.
Hydro unit LEV1
SV1
WP1
*The indoor unit fan will stop during defrost.
BS_05_E
Condition 1
-5ºC [23ºF] or above
50 minutes or more
90 minutes or more if the defrost prohibit timer is set to 90.
The evaporating temperature
has stayed below the tempera-
ture in the table below (Note1)
for 3 minutes
(E)M200 - 300 (E)M350 - 500
-13 ºC -11 ºC
-8 ºC -8 ºC
1500 pulses (M200–300), 3000 pulses (M350–500, EM200–500)
3000 pulses (M200–500, EM500), 41 pulses (EM200–450)
ON (Bypass defrost)
Condition 2
-5ºC [23ºF] or below
(Te ≤ 1.1 × TH7 - 7.5) continued
for 3 minutes or [{1.5 + 0.02 x
(20+TH7)} > 63LS] continued
for 3 minutes
Stopped
ON
OFF
OFF
ON
ON
OFF (Closed)
ON (Open)
OFF (Open)
0 pulses
3000 pulses (M500, EM500)
0 pulses
DIP SW 001-10
41
ON
Normal control
Condition 3
250 minutes or more
The evaporating temperature
has stayed below the tempera-
ture in the table below (Note1)
for 3 minutes
*2
OFF (Heat recovery defrost)
3000
OFF
Command value 100%
25
chapter 5 -