Mitsubishi Electric PURY-P72 Service Handbook page 143

[ VII Control ]
(5) Bypass solenoid valve (SV5b) (ON = Open)
Operation
While the unit is stopped
Cooling mode
Others
-6- Compressor 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, and condensing temperature (49°C [120°F] = 2.88 MPa [418 psi])
during heating 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.
Model
P72 model
P96 model
P120 model
The maximum frequency during heating operation is affected by the outdoor air temperature to a certain extent.
(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 or the completion of defrost operation
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).
HWE0803A
ON
When one or more of the following
valves is turned OFF: SV4a
through SV4c.
Frequency/cooling (Hz)
Max Min
43 14
65 18
75 18
- 134 -
SV5c
OFF
Always ON
When the condition on the left is not
met
Always OFF
Frequency/heating (Hz)
Max Min
48 19
71 15
85 15
GB