Mitsubishi Electric CITY MULTI PUHY-400YMF-C Service Handbook page 68

[1]-2 PUHY-400·500 YMF-C
(1) Initial processing
• When turning on power source, initial processing of microcomputer is given top priority.
• During initial processing, control processing corresponding to operation signal is suspended. The control
is resumed after initial processing is completed. (Initial processing: Data processing in
processing
microcomputer and initial
(2) Control at staring
• For 3 minutes after starting, 60 Hz is the upper frequency limit. (When only No. 1 compressor is operating.)
• 75 Hz is the upper limit within 2 hours after the power supply has been turned ON and for the 30 minutes after the
compressor has started operation.
• Normal control is performed after the initial start mode (described later) has been completed.
(3) Compressor capacity control
• Variable capacitor compressor is performed by the variable capacity compressor (No. 1: inverter motor) and
constant capacity compressor (No. 2: Model 500 has capacity control switching, Model 400 does not).
• In response to the required performance, the number of compressors operating, the switching of capacity control
and the frequency of the variable capacity compressor is controlled so that the evaporation temperature is
between 0 and 5˚C in cooling mode and that the high pressure is between 1.76 and 1.96 MPa in heating mode.
• The fluctuation of the frequency of the variable capacity compressor is as follows. It is performed at 2 Hz per
second.
20 to 100 Hz (TH6 > 20˚C and in cooling mode, or in heating mode)
30 to 100 Hz (TH6 < 20˚C and in cooling mode)
1) No. 2 compressor operation, stopping and full-load/un-load switching
1
Switching from stopping to operation of No. 2 compressor.
When the required performance cannot be obtained by only No. 1 compressor, the No. 2 compressor will be
started. (On Model 500, the No. 2 compressor will be started in un-load operation.)
• Model 400: After the No. 1 compressor has reached 98 Hz, the No. 2 compressor stops
• Model 500: After the No. 1 compressor has reached 100 Hz, the No. 2 compressor stops
full-load.
2
Switching from operation to stopping of No. 2 compressor.
When the required performance is exceeded when the two compressors, No. 1 and No. 2, are operating, the No.
2 compressor is stopped. (On Model 500, the No. 2 compressor will be performed in un-load operation.)
3
Switching from un-load to full-load of No. 2 compressor (Model 500 only)
When the required performance cannot be obtained by the No. 1 compressor and the No. 2 compressor operat-
ing in un-load, the No. 2 compressor will be switched to full-load operation.
4
Switching from full-load to un-load of No. 2 compressor (Model 500 only)
When the required performance is exceeded when the two compressors, No.1 and No. 2 operating in full-load,
the No 2 compressor will be switched to un-load operation.
2) Pressure control
The upper limit value for the high pressure (Pd) has been set for each frequency. When this value is exceeded,
the frequency is reduced every 30 seconds.
3) Discharge temperature control
The discharge temperature of the compressor (Td) is monitored during the operation. If the upper limit is exceeded,
the frequency is reduced by 5 Hz.
• Control is performed every 30 seconds after 30 seconds at the compressor starting.
setting of each LEV opening, requiring approx. 2 minutes at the maximum.)
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starts.
un-load or un-load