Frequency Control - Mitsubishi Electric R410A Service Handbook

[5-2 Outdoor Unit Control ]
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.
Model
72 model
96 model
120 model
144 model
168 model
The maximum frequency during heating operation is affected by the outside air temperature and the dipswitch settings to
some 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).
HWE14080
Frequency/cooling (Hz)
Max Min
52 10
65 10
74 16
97 16
111 16
- 96 -
Frequency/heating (Hz)
Max Min
57 10
80 10
83 16
107 16
120 16
GB