Mitsubishi Electric City Multi PUHY-HP144TSHMU-A, Service Handbook

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[
VII
Control ]
- 87 - HWE0716A GB
-7- Defrost Operation Control
(1) Starting the defrost operation
Œ
The defrost cycle starts when outdoor temperature, integrated operation time of compressor, and piping temperature are met
for every range of <condition 1> through <condition 3>.
ΠDefrost cycle does not start while other outdoor units are defrosting or 10 minutes have not passed since resuming operation
after the completion of the defrost cycle.
Œ
If 10 minutes have passed since compressor start-up or since the completion of defrost operation, forced defrost operation
will start by turning on the forced defrost switch (DIP SW2-7).
ΠEven if the defrost-prohibit timer is set to 90 minutes or 150 minutes <condition 3>, the actual defrost-prohibit time for the next
defrost cycle is 50 minutes if the last defrost cycle took 12 minutes.
Œ
In the multiple-outdoor-unit system, all of the outdoor units that are in operation go into the defrost mode simultaneously. The
unit(s) that is stopped at the time defrost operation starts remains stopped.
(2) Defrost operation
(3) Stopping the defrost operation
ΠThe defrost cycle ends when 12 minutes have passed since the beginning of the cycle, or when the pipe temperature (TH3)
is 10°C[50°F] or above has been continuously detected for 2 minutes.
Œ
The defrost cycle does not end for 2 minutes once started unless the pipe temperature exceeds
ǩ
below within 2 minutes.
25°C ( ǩ = Outdoor temperature(TH7) - 25)°C 5°C [77°F ( ǩ = Outdoor temperature(TH7) - 45)°F 41°F]
ΠIn the multiple-outdoor-unit system, defrosting is stopped on all units at the same time.
(4) Problems during defrost operation
ΠIf a problem is detected during defrost operation, the operation will be stopped, and the defrost prohibition time based on the
integrated compressor operation time will be set to 20 minutes.
(5) Change in the number of operating indoor units during defrost operation
ΠEven when there is a change in the number of operating indoor units during defrost operation, the operation will continue, and
an adjustment will be made after the completion of the defrost operation.
Œ
Defrost operation will be continued, even if the indoor units stop or under the Thermo-OFF conditions until it has run its course.
<condition 1> <condition 2> <condition 3>
Outdoor temperature (TH7) - 5°C [23°F] and above - 5°C [23°F] or below
Integrated operation time of
compressor When 50 minutes have passed (90 minutes when the de-
frost-prohibit timer is set to 90 minutes). When 250 minutes have
passed
Piping temperature (TH3) At or below -10°C [14°F] for
3 minutes
Or {(1.5+0.02 XTH7>63LS)
for 3 minutes Outdoor temperature (TH7)
is at or below -5°C [23°F] for
3 minutes
Or {(1.5+0.02 XTH7>63LS)
for 3 minutes. At or below -10°C [14°F] for
3 minutes
Compressor frequency Model Compressor frequency
HP72 model 60 Hz
HP96 model 60 Hz
Outdoor unit fan Stopped
SV1a ON
SV2 OFF
SV6 OFF
SV9 OFF
21S4a OFF
LEV1 200 pulses
LEV2a , LEV2b 1400 pulses
LEV4 460 pulses