Mitsubishi Heavy Industries SRK25GZ-L1 Handbook page 1043

(17) Compressor operating frequency increase control
(a) In the case that at least one in-door unit requires the maximum frequency supply during cooling or heating operation for 6
minutes continuously, the compressor operating frequency is increased by 10 Hz. After that, the maximum frequency is
increased by 10 Hz every continuous 6 minutes; however, the upper limit is 30 Hz.
(b) When requirement of the maximum frequency ceases, the control is released.
(c) When the protective function of frequency suppressing is activated during control, the protective motion is performed at the
condition of increased frequency as the base.
(Example: When the current safe is activated at the condition of +20 Hz compensation)
Required Hz
from in-door unit
Compressor
operating Hz
(18) Control at heating change over
When one of the in-door units is changed over from "Cooling (including automatic), dehumidification and ventilating mode" to
"Heating (including automatic) mode", or from "Heating mode" to "Cooling, dehumidification and ventilating mode", the
following control is performed.
(a) During compressor is operating
1) The heating output is kept at the output condition just before cooling/heating change over for 2 minutes and 45 seconds,
after that the heating output of in-door unit where cooling/heating has been changed is changed over.
2) The 4 way valve (20SL, 20SS) is changed over at 2 minutes after the compressor stopped.
3) The compressor starts operation with the operation pattern shown in the following diagram after 3 minutes' stop.
In-door
unit
4 way valve
(20SL, 20SS)
(b) When the compressor has kept on stopping for 2 minutes and 45 seconds or more:
1) The heating output is changed over immediately.
2) The motion of compressor and 4 way valve is the same manner as described in Article (a).
(c) When the stop time of compressor is less than 2 minutes and 45 seconds:
1) The heating output is changed over after 2 minutes and 45 seconds has passed since the compressor stop.
2) The motion of compressor and 4 way valve is the same manner as described in Article (a).
50
Current safe
40
30
60
50
40
Heating
Operation
mode
Cooling
ON
Heating
output
OFF
ON
Compressor
OFF
2 min.
ON
or
OFF
Current safe released
2 min. and 45 sec.
3 min.
Initial operation
pattern
FDC-HKXR
In-door unit
requirement
With +20 Hz
compensation
Without +20 Hz
compensation
2 min. and 45 sec.
3 min.
2 min.
Initial operation
pattern
1041