Mitsubishi Heavy Industries SRK25GZ-L1 Handbook page 831

(b) Compressor protection control
(i) Start of compressor protection
1) Inverter is operated at the frequency not exceeding the upper limit of 65 Hz for 1 minute and 45 seconds after the start in order
for protection of compressor and then changes the frequency to the selected frequency. CM2 (for 224, 280) is stopped for the
same period of 1 minute and 45 seconds. If the selected frequency is lower than 65 Hz, the operation continues at the same
frequency. However, at the initial start of inverter after turning power ON or starting 6 hours or more after stopping the compres-
sor, the frequency is raised at a rate of 5 Hz/minute starting from 25 Hz for 12 minutes.
(ii) Compressor protection at high frequency
If operation is maintained at 95 Hz or higher for 9 minutes continuously, the frequency is reduced to 90 Hz. The operation
continues for 1 minute at the frequency and, if the required frequency of indoor unit is reduced to below 90 Hz by the protective
control or others in the mean time, the operation continues at such frequency. After operating at 90 Hz, the frequency is raised
at a rate of 5 Hz per 10 seconds.
(iii) Compressor start delay (3-minute timer)
When the inverter compressor (CM1) has been stopped due to the cooling (heating) thermostat operation, by the remote control-
ler start switch, error or others, the compressor start is disabled from 3 minutes. However, the 3-minute timer becomes invalid
when the power switch has been turned on.
Compressor (CM2) also does not start for 3 minutes after the stop and, if it has been started and stopped, then it cannot be started
for 6 minutes after the start.
(iv) Operation with equal amount of oil (Only for 224, 280 models)
After the CM2 has been operated continuously for 3 hours, the following operations take place:
Step 1: CM1 is operated at 40 Hz with CM2 ON for 3 minutes.
Step 2: CM1 is operated at 90 Hz (224) or 95 Hz (280) with CM2 OFF for 3 minutes.
(c) Crankcase heater power on detection control
With this control, duration of time when power has been turned ON (CH power on) is accumulated and, when operation is started
earlier than 6 hours, frequency is controlled as follows.
(i) Purpose of this control is to protect the compressor dilution ratio at the time of soak out on the compressor.
When the service switch (SW3-3) is turned OFF (setting at shipping), the following controls are performed.
This control is invalid when the switch is turned ON.
1 When the external temperature (Tho-A) and under-dome temperature (Tc) are in the shadowed area in the following figure, the
compressor will not be started.
2 Compressor will be started if either one of the following conditions is met.
a) 6 hours after power ON
b) Service switch (SW3-3) ON
c) When temperatures run out the shadowed area in the step 1.
3 While the compressor is stopped by this control, the following data are displayed on the 7-segment display regardless of setting
of the display selector switch (SW4).
• Immediately after power ON, specify as "360" and the number is reduced by "3" at every 3- minute.
(This corresponds to 6 hours after power ON and indicates remaining number of minutes.)
46˚C
Tc
6˚C
0˚C
Tho-A
40˚C
FDC-HKX
829