Mitsubishi Electric PFD-P250VM-E, Service Handbook

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[5-2 Outdoor Unit Control ]
BS_05_C chapter 5 -
11
5
Cont
rol
5-2-6 Frequency Control
 Depending on the capacity required, the frequency of the compressor is controlled to keep constant evaporation temperature
(0°C [32°F] = 0.71 MPa [103 psi]) during cooling operation.
 The table below summarizes the operating frequency ranges of the inverter compressor during normal operation.
 The OS in the multiple-outdoor-unit system operates at the actual compressor frequency value that is calculated by the OS
based on the preliminary compressor frequency value that the OC determines.
(1) Pressure limit
The upper limit of high pressure (63HS1) is preset, and when it exceeds the upper limit, the frequency is decreased every 15
seconds.

The actuation pressure is when the high-pressure reading on 63HS1 is 3.58MPa[519psi].
(2) Discharge temperature limit
Discharge temperature (TH4) of the compressor in operation is monitored, and when it exceeds the upper limit, the frequency
is decreased every minute.
 Operating temperature is 115°C [239°F].
(3) Periodic frequency control
Frequency control other than the ones performed at start-up, upon status change, and for protection is called periodic frequen-
cy control (convergent control) and is performed in the following manner.
Periodic control cycle
Periodic control is performed after the following time has passed

30 seconds after either compressor start-up
 30 seconds after frequency control based on discharge temperature or pressure limit
The amount of frequency change
The amount of frequency change is controlled to approximate the target value based on the evaporation temperature (Te) and
condensing temperature (Tc).
5-2-7 Refrigerant Recovery Control
Recovery of refrigerant is performed during cooling operation to prevent an excessive amount of refrigerant from accumulating
in the outdoor heat exchanger.
(1) During cooling operation
Starting refrigerant recovery mode
The refrigerant recovery mode starts when all the following conditions are met:
 30 minutes have passed since the completion of previous refrigerant recovery.
 When the unit keeps running for 3 minutes in a row or more with high discharge temperature
 TH4 > 105°C [221°F] or 63HS1 > 3.43 MPa [497 psi] (35 kg/cm
2
G) and SC0 > 10°C [50°F]
Refrigerant recovery
The opening of LEV1 is increased and periodic control begins again.
Model
Frequency/cooling (Hz)
Max Min
250 model
*PFD-P250VM-E
61 10
250 model
*PFD-P500VM-E
Two refrigerant circuits
65 10
500 model
*PFD-P500VM-E
Single refrigerant circuit
130 10
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