[ VII Control ]
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HWE1018A GB
-6- Compressor Frequency Control
Depending on the capacity required, the frequency of the compressor is controlled to bring the evaporation temperature (Te)
close to the target evaporation temperature (Tem) during cooling operation, and to keep constant condensing temperature
(49°C[120°F] =2.88MPa[418psi]) during heating operation.
The target evaporation temperature (Tem) varies as follows during cooling operation depending on the capacity required.
When the capacity exceeds the needs : Tem is lowered.
When lacking in capacity : Tem is raised.
Minimum and maximum Tem Valued : -10°C[14°F] Tem < 25°C[77°F]
(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).
Model
Frequency/cooling (Hz) Frequency/heating (Hz)
Max Min Max Min
250 model 56 10 63 10
500 model 112 10 126 10
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