Mitsubishi Electric PURY-P72 Service Handbook page 155

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[ VII Control ]
Compressor Frequency Control
-6- Compressor Frequency Control
ŒDepending 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, and condensing temperature (49°C [120°F] = 2.88 MPa [418 psi])
during heating operation.
ŒThe table below summarizes the operating frequency ranges of the inverter compressor during normal operation.
ŒThe 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.
Model
P72 model
P96 model
P120 model
P144 model
The maximum frequency during heating operation depends on the outside air temperature and the dipswitch settings.
(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.
ŒThe 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.
ŒOperating 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
Œ30 seconds after either compressor start-up or the completion of defrost operation
Œ30 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).
HWE1116D
Frequency/cooling
Max
Min
43Hz
12Hz
61Hz
16Hz
75Hz
16Hz
87Hz
16Hz
- 146 -
Frequency/heating
Max
Min
71Hz
27Hz
98Hz
29Hz
107Hz
29Hz
107Hz
29Hz
GB
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