Processing At Overheat Thermistor (Oh) High Temperature; Restriction Start Conditions; Restriction Release Condition (In Common For All) - Hitachi RAM-52QH5 Service Manual

MODEL RAM-52QH5

PROCESSING AT OVERHEAT THERMISTOR (OH) HIGH TEMPERATURE

Restriction Start Conditions

If any expansion valve is operated at 480 pulses and the OH temperature > [NDOWN_ON], the compressor speed will be
reduced at a rate of 100 min
This reduced rotation speed is based on the speed when the reduction started, and will be maintained until the reduction is
finished. However, the reference speed will be exchanged only if the target speed is lower than the speed when the
reduction started.
If [NDOWN_OFF] ≤ OH temperature ≤ [NDOWN_ON] and the OH temperature does not rise from that 20 seconds
before, the reduction of compressor speed will not occur.

Restriction Release Condition (in common for all)

The restriction will be released when OH temperature < [NDOWN_OFF], and the compressor speed will be increased at a
-1
rate of 50 min /30 seconds to restore the target speed.
When two units are operated for heating:
Unit 1
Unit 2
Cooling output
Heating output
Turns on
for cooling
Outdoor fan
[EDWN_ON]
[EDWN_OFF]
WMAX2
Compressor
rotation speed
20 sec.
520
480
Hold
Unit 1
Hold 500ms
0
520
480
Hold
Unit 2
Hold 500ms
0
Operation with one unit in heating or cooling mode and with two units in cooling mode is the same as in the above diagram.
WMAX2 and MINRPM are EEPROM data.
-1
/30 seconds.
Decreases by 100 min
20 sec.
-1
/30sec. Increases by 50 min
MINRPM
– 67 –
-1
/30sec.
20 sec. 20 sec. 20 sec.
WMAX2