Panasonic U-72MF2U9 Service Manual page 14

3. Compressor Control
3. Compressor Control
3-2-2. Operating compressors
When heat exchanger of the outdoor unit is condenser (All cooling mode or mixed cooling/heating)
The compressor with higher priority order starts according to the priority order described on the compressor
selection rules.
Outdoor air temperature＜50°F (10°C): More than one compressor among all outdoor units will be operated.
When heat exchanger of the outdoor unit is evaporator (All cooling mode or mixed cooling/heating)
At least, one inverter compressor operates when the system starts.
The other compressors operate according to the priority order described on the compressor selection rules.
3-2-3. Stopping compressors
The compressor with lower priority order starts according to the priority order described on the compressor
selection rules.
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3-3. Operation When Starting 2 Compressors Mounted in Outdoor Unit
When necessary capacity gradually increases and one more inverter compressor is additionally started under
the present operating compressor, reduce the compressor frequency to 25Hz temporarily and then start an
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additional compressor.
The operation noted above is performed when 1st compressor or 2nd compressor is additionally started.
If necessary capacity is initially higher and two compressors are started simultaneously, the operation noted
above is not performed and both of them are regarded as the target frequency.
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3-4. Operating Frequency Range of Inverter Compressor
The inverter compressor can operate within the range in the table below.
1 When the high pressure is over 435psi (3.0MPa), the upper limit frequency is 90Hz.
2 If the high pressure is over 450psi (3.1MPa) and the minimum frequency operation is in progress, the system
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is stopped. (P25: Pre-trip)
3 If the low pressure is over 213psi (1.47MPa) during operation of the inverter compressor, the system is stopped.
(P27: Pre-trip)
4 If 2 inverter compressors are simultaneously operating in the same outdoor unit, the frequency of 1st
compressor becomes 5Hz lower than that of 2nd compressor.
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Type of outdoor unit
Minimum frequency (Hz)
Maximum frequency (Hz)
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* The frequency range in the table above is subject to change without notice.
3-5. Forced Stopping of Compressor
Once a compressor stops, it will not start for a period of 3 minutes (3-minute forced OFF).
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However, this does not apply when the compressor was forced to stop as the result of a special control operation.
(start control, defrost control, refrigerant oil recovery control, etc.)
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72 96
15 15
100 100
1 - 6
2WAY VRF SYSTEM
3WAY VRF SYSTEM
Control Functions
Control Functions
120 144
15 15
100 100