Mitsubishi Heavy Industries SRK25GZ-L1 Handbook page 830

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(e) Compressor operation frequency UP control
1) If any indoor unit demands the maximum frequency for more than 3 minutes continuously during heating operation (pro-
vided either one of the following conditions is met), the compressor operation frequency will be increased by 5 Hz. Further
increase of 5 Hz will repeat at each time when the maximum frequency is maintained for 3 minutes. However, the frequency
will not rise beyond the upper limit of 30 Hz.
• When there are more than one units of indoor blower of which the thermostats are turned OFF or which are blowing.
• When one or more units have stopped heating.
• When the outdoor temperature is below 0˚C.
2) This control is released when the required frequency becomes lower than the maximum frequency.
3) When the protective function that suppresses the frequency is actuated during the control, the protective motion takes place
based on the condition in which the frequency has been raised.
(6) Compressor operation frequency UP/DOWN control
(a) When operation starts from the state that the compressor inverter being stopped (CM1), the frequency starts from 5 Hz and rises
in the unit of 1 Hz up to 25 Hz.
(b) The frequency is changed at a rate of 2 Hz per second at the inverter side for both UP and DOWN. However, if the frequency
is specified to be 0 Hz, the operation is stopped immediately.
(c) Inverter frequency is fixed in the range of 25 to 100 Hz. Frequency increases at a rate of 5 Hz/sec in this range.
(7) Compressor start/stop control
(a) Inverter compressor (CM1) will be stopped immediately upon receipt of stop command from the indoor unit or by a serial
signal error and when the protective function is actuated on the controller of the unit or inverter.
(b) If the inverter compressor (CM1) is stopped, the non-inverter compressor (MC2) (for models 224 and 280) will be stopped
simultaneously.
(8) 4-way valve switching assurance
At the start of inverter compressor (CM1), the following operations take place regardless of selected frequency.
(a) 5 ~ 25 Hz operation
It is operated in the range of 5 ~ 25 Hz. In this operation, however, the compressor cannot be operated with the current safe or
high pressure controls or discharge pipe control.
(b) 25 ~ 65 Hz operation (only for 224, 280 models)
Maximum frequency is determined based on the temperature detected with the outdoor air temperature sensor (Tho-A).
1) Below 0˚C : Maximum frequency is 90 Hz. Operation takes place at 90 Hz for 45 seconds after the start.
2) Above 0˚C : Maximum frequency is 65 Hz. Operation takes place at 65 Hz for 32.5 seconds after the start.
However, if conditions to start the current safe or high pressure controls or discharge pipe temperature control are met in the mean
time, this control is terminated and substituted with the current safe or high pressure controls or discharge pipe temperature control
which determines the compressor frequency. When the latter control is released, the operation returns to the normal mode.
(9) Equipment related to unit protection and maintenance
(a) Test run mode [Outdoor unit adaptation]
1) Test run operation mode is controlled from outdoor using switches SW3-5 , 6 which are provided on the outdoor unit control
PCB. (This is independent from CnS.)
Functions of switches
Switch
• All indoor units on the connection are operated.
ON
SW3-5 • Indoor unit demands the maximum frequency and the outdoor unit is operated at the maximum frequency ((a) 2) according to the demand from the indoor unit.
OFF • Normal operation
ON SW3-5ON : Cooling operation
SW3-6
OFF SW3-5 ON : Heating operation
Note (1) This operation is dominant over other options such as the center console, etc. Operation status is transmitted to the optional equipment.
2) Upper limit of frequency during test run operation
Upper limit of frequency is equal to the sum of maximum required frequencies (Hz) of units on the connection.
3) During the test run operation, there is no fuzzy control but other controls are effective. Remote controller displays the
operation status and a word "Center".
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Function