Mitsubishi Electric PURY-P120TJMU-A, Service Handbook, Page: 155 / 411

[
VII
Control ]
- 146 - HWE0913A GB
(5) Bypass solenoid valve (SV5b) (ON = Open)
-6- Compressor Frequency Control
Œ
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.
Œ
The table below summarizes the operating frequency ranges of the inverter compressor during normal operation.
Œ
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.
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.
Œ
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.
Œ
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
Œ
30 seconds after either compressor start-up or the completion of defrost operation
Œ
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).
Operation
SV5c
ON OFF
While the unit is stopped Always ON
Cooling mode When one or more of the following
valves is turned OFF: SV4a
through SV4c. When the condition on the left is not
met
Defrost mode Always OFF on the P72 and P96 models and
always ON on the P120 and P144 models.
Others Always OFF
Model
Frequency/cooling (Hz) Frequency/heating (Hz)
Max Min Max Min
P72 model 43 14 52 19
P96 model 61 18 74 15
P120 model 75 18 86 15
P144 model 87 18 104 15