Carrier MMY-MAP0724FT9UL Service Manual page 64

NO. Item
7
Defrosting 1. Defrosting commencement conditions
control
• During heating operation, the cumulative duration of operation in which TE1
(reverse
defrosting
method)
2.
1) All compressors currently in operation are operated at the minimum speed.
2) When a specified amount of time passes from the time the compressors reached
3) All compressors currently not in operation are turned on and operated at the
3. Defrosting termination conditions
• Defrosting termination conditions are met when the TE1 temperature sensor
4. Details of defrosting termination control
1) Compressors are operated at the standby operation speed.
2) When a specified amount of time passes, the 4-way valves are opened.
3) Indoor heating refrigerant recovery control is performed.
For control details, see " 6. Refrigerant/oil recovery control".
Specification outline
sensor temperature falls below frost formation temperature is measured, and
when this reaches 55 minutes, defrosting control is introduced. (Just after
startup or upon changeover from cooling to heating, the target cumulative
duration is 25 minutes.)
* If the outdoor units are a combination of different models, all the units begin
engaging in defrosting control as soon as one of them satisfies defrosting
commencement conditions.
Details of defrosting control
the minimum speed, the outdoor fans are turned off by closing the 4-way valves.
target rotational speed for defrosting control.
measurement reaches a specified value (roughly 53.6°F (12°C)) a certain period
of time after the commencement of defrosting control. In that event, defrosting
termination control takes over.
* If the outdoor units are a combination of different models, defrosting
termination control commences when all the units satisfy the defrosting
termination conditions.
As long as one or more outdoor units are yet to satisfy the defrosting
termination conditions, those that have engage in standby operation.
– 64 –
Remarks
• Frost formation
temperature is
30°F (–1°C).
• If the outdoor
units are a
combination of
different models,
defrosting
operation, once
started, cannot
be manually
terminated for
about 2 minutes.
• To protect the
refrigerating cycle
circuit, the fan
mode may be
controlled during
defrosting.
• During defrosting
control,
compressors are
controlled so that
their speeds do
not exceed 70
rps.
• During standby
operation,
compressor
speed is in the
24-33.5 rps
range.
(It varies from
outdoor unit to
outdoor unit.)