Mitsubishi Electric PUHY-P1000, Service Handbook

Page: 104 / 334

[5-2 Outdoor Unit Control ]
- 95 -
HWE14040 GB
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, 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.
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).
Operation
SV11
ON OFF
When Continuous heating
mode P200-P400: Top part of heat exchanger is
being defrosted.
P450-P500: Right part of heat exchanger
is being defrosted. Other than on the left
Model
Frequency/cooling (Hz) Frequency/heating (Hz)
Max Min Max Min
200 model 52 10 56 10
250 model 65 10 71 10
300 model 74 16 88 16
350 model 91 16 105 16
400 model 97 16 110 16
450 model 111 16 122 16
500 model 123 16 129 16