Service manual
2.
High pressure
protection
During heating operation the solenoid valve for injection and the outdoor fan motor are controlled by the temperature of the
indoor coil thermistor RT12 for excess rise protection of compressor discharge pressure.
Indoor
coil
tlwmktw
RT12 MSH-09 MSH-12 MSH-15
126F 722'F 733'F
turn
Outdoor OFF
fan
motor
I
Outdoor fan
motor
121'F 117'F 127'F
turn
ON
Injection
sdenoid
coil
turn
OFF
115'F
-
-
injection
sdenoid
mii
ON
'
lnjmim
md
wit
Outdoor
fan
motor
This high pressure protection control is as below.
11
'
NOTE
:
When the outdoor fan is off, the heating defrost is not detected bv the defrost thermistor RT61.
Defrosting
Outdoor unit defrosting is controlled by outdoor
P.C.
board,
it
is detected by the defrost thermistor RT61 and discharge temp.
thermistor RT62.
Defrost starting conditions
When all conditions of a)
--
dl are satisfied, the defrosting operation starts.
a) Under heat mode of
"I
FEEL CONTROL" and heat operation, the compressor cumulative time exceeds the defrost interval.
b) The defrost thermistor RT61 is below 27°F.
c) After releasing the high pressure protection of the outdoor fan operation, 180 sec
:
MSH-OSDW or 256
sec
:
MSH-12/
15DN elasped.
d) Regarding MSH-12/15DN, discharge temp. ttiermistor RT62 is below 185°F.
Defrost stopping conditions
When the condition
e) or
f)
is satisfied, the defrosting operation stops.
e) The defrost thermistor RT61 is above 37°F.
f) The defrosting time exceeds 10 min.
The defrosting operation stops forcedly by timer.
Defrost interval
The defrost interval is calculated by defrosting time.
1. After starting of heating operation, the first and second defrost interval are fixed to 60 min.
2. From the third interval,
it
is calculated
so
as that defrost time is 2 min.
Model
MSH-OSDW
MSH-12DN
MSH-15DN
Outdoor
fan
I
Defrost
Time
I
Defrost
Interval
I
High pressure protection time chart
ON
121'F
117'F
127°F
OFF
126F
122'F
133°F
under 2 min.
2
--
3 min.
Previous interval plus 10 min.
Same as previous
3
-
4
min.
over
4
min.
Previous inteml minus 10 min.
Previous interval minus 20 min.
Mode
3.
Max. and Min. of Defrost Interval
MSH-OSDW
Max.
1
40 min.
MSH-12DN
I
MSH-I5DN
Min.
120 min.
20 min.