Defrosting - Mitsubishi Electric MSH09TW Service Manual

3. Defrosting (Refer to page 70 for MXZ30TN MXZ30TN2)
Defrosting of outdoor heat exchanger is controlled by deicer P.C. board, which detection by the defrost thermistor RT61.
(1) Starting conditions of defrost
When all conditions of a) ~ c) are satisfied, the defrosting operation starts.
a) Under the heat operation, the compressor cumulative operation time exceeds 40 minutes (MSH09TW, MSH12/15/
17TN) /15 minutes (MSH09TW -
working.
b) The defrost thermistor RT61 reads 27˚F or less (MSH09TW, MSH12/15/17TN) / 32°F or less (MSH09TW -
MSH12/15/17TN-
c) After releasing the high pressure protection 4 minutes and 15 seconds have elapsed.
(2) Releasing conditions of defrost
When the condition d) or e) is satisfied, the defrosting operation stops.
d) The defrost thermistor RT61 reads 38˚F or more (MSH09TW, MSH12/15/17TN) / 50°F or more (MSH09TW -
MSH12/15/17TN-
e) The defrosting time exceeds 10 minutes.
(3) Defrosting time chart
Defrost thermistor RT61
50°F or more
(MSH09TW - U1 , MSH12/15/17TN-
MSH12/15TN- )
U2
38˚F or more
(MSH09TW, MSH12/15/17TN)
32°F or less
(MSH09TW - U1 , MSH12/15/17TN-
MSH12/15TN- )
U2
27°F or less
(MSH09TW, MSH12/15/17TN)
ON
Outdoor 52C
contactor(Compressor)
OFF
ON
X62
(R.V. coil)
OFF
ON
SR61
Outdoor fan
OFF
ON
Defrost
counter
OFF
ON
Indoor fan
OFF
Horizontal
Indoor vane
Set position
NOTE: When the indoor coil thermistor RT12 reads above 64˚F, indoor fan operates at Very Low for 30 seconds since
RT61 has read the working temperature of defrosting.
When the indoor coil thermistor RT12 reads 64˚F or less, the indoor fan stops.
, MSH12/15/17TN-
U1
, MSH12/15TN- ).
U1 U2
, MSH12/15TN- ).
U1 U2
U1 ,
U1 ,
15 sec.
30 sec.
NOTE
, MSH12/15TN- ) without the defrosting operation
U1 U2
Max 10 min.
59
U1
30 sec.
5~15 sec.
,
,
U1