Control Function - Haier MRV 5-RC VP1-112B Service Manual

3. Control function

3.1 Compressor control
3.1.1 Cycle start function of compressor
(1) According to different load of indoor unit, determine the starting number of compressors and outdoor unit
(2) If there is only 1 outdoor unit with 2 compressors, shift the priority of compressor 1 and 2 every 4 hours.
(3) If there are several outdoor units, the priority of these outdoor units shall be shifted every 8 hours.
(4) There are no fixed master or slaves in the MRVIV-C series system, and they are switched in turn according to
the conditions.
3.1.2 Changes of the number of compressor
(1) In one outdoor unit, when one compressor operating frequency reaches 75%, another one compressor is
started. When the output ratio of two compressors drops to 25%, one of the compressors is stopped;
(2) In the multiple outdoor units combination system, when the output ratio of one outdoor unit reaches 75%,
another outdoor unit is started. When the total output ratio of all the outdoor units drops to 25%, one outdoor unit is
stopped.
3.1.3 Compressor start delay
(1) In the control of the compressor, in order to prevent the starting at differential pressure, it must take some time
to balance the high and low pressure after stopping fully, the restarting will delay automatically, and the compressor
can restart after stopping for 3 to 5 minutes.
(2) When power on, it shall delay 3~5 min to restart the compressor.
(3) Before restart the compressor, when the oil temperature cannot meet the start requirement, it will delay the start
until oil temperature can meet the requirement.
3.1.4 Compressor crankcase heater control
When the compressor is stopped, in order to prevent the refrigerant from dissolving in the compressor oil and
diluting the compressor oil, the compressor oil temperature must be controlled at a certain value or more.
Even if the compressor is in operation, if the compressor oil temperature is too low, the heater is energized to heat
it.
3.1.5 Compressor start protecting control:
(1) Based on the superheat of the oil temperature of the compressor or the heating time of the heater after the
power is turned on to determine whether to start the compressor. The purpose of this control is to prevent the oil of
the compressor that has been stopped for a long time from being severely diluted by the refrigerant.
(2) Compressor start protection control: In the first three minutes of start-up, the compressor's operating frequency
is kept at 50 rps or 60 rps.
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