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The following is a brief outline of the testing of the defrost
system.
1. Defrost sensor must be closed, 32°F or below. If
temperatures are such that the switch will not close,
jumper between defrost sensor terminals on the defrost
control.
2. Start system in heating operation.
3. Jumper test pins. A 1/4" quick connect terminal crimped
onto a solid wire or brazing rod works well for a test
jumper. Closing test pins speeds up time interval by a
factor of 256.
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After closing test pins and appropriate cycle time has
elapsed, the reversing valve should shift to defrost mode
and the outdoor fan should stop. After 2 seconds of defrost
operation, the reversing valve should shift back to heating
operation and the outdoor fan should start.
Quiet Defrost Feature
The defrost control in this appliance is equipped with a quiet
defrost feature. With the jumper pin set at the DLY position, at
the start of the defrost cycle, the defrost control will energize
the reversing valve solenoid and de-energized the outdoor fan,
and de-energize the compressor circuit a period of 10 seconds.
The result is a much quieter defrost cycle.
CAUTION
For reliable operation, all MHP9A12 models must always
have the jumper pin in the NORM position.
All units have the jumper pin set at the NORM position.
PS1 and PS2 terminals: These appliances are not equipped
with a pressure switch in the refrigeration system. Therefore,
the jumper on the NOPS pin is factory installed and required.
506325-01
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System Performance
For maximum performance of this heat pump system, the
operating temperatures and pressures should be checked
and superheat determined at Standard ARI test conditions
of 82°F outdoor – 80°F indoor dry bulb/67°F wet bulb. If
superheat measured deviates from the values given in
Table 4, refrigerant charge should be adjusted accordingly
for maximum performance.
i T
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Issue 0941
Suction Superheat
Suction Superheat
@ ARI Conditions
Magic-Pak
®
Model
80° IDDB/67° IDWB
MHP4-09-12
MHP4-09-18
MHP4-09-24
MHP4-09-30
MHP4-09-36
MHP4-10-18
MHP4-10-24
MHP4-10-30
Table 4
82° OD
15-18
9-11
17-19
11-13
23-25
8-10
16-18
24-26
Page 9 of 18
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