Haier HBU-18HF03 Manual page 238

sensor will check the indoor coil temperature, and send the temp. to outdoor; if indoor coil temp.
>T1 （53℃） , the outdoor motor will enter low speed; if indoor coil temp.＜T2 （50℃） , outdoor motor
will enter high speed; if indoor coil temp. >T3（56℃）, outdoor motor will stop; if indoor coil temp.
＜T4（53℃）, outdoor motor will resume low speed; when indoor PCB receive the signal of outdoor
motor stop from outdoor PCB over 2 minutes, if indoor coil temp. >T6（70℃）or 10 minutes later
indoor coil temp. >T5（56℃）, send compressor stop signal to outdoor unit; if indoor coil temp.＜46
℃ and the compressor has stopped over 3 minutes, send compressor run signal to outdoor unit,
and compressor resume to normal.
The outdoor motor is control by oudoor unit.
4.3 Over current protection
4.3.1 In heating mode
After compressor running for 40 seconds, if the current thermostat has measured that system
working current is more than 21A and keep it for 5 seconds, outdoor motor will convert into low
speed; if working current is less than 18A, it will resume to high speed; if working current is more
than 25A and keep it for 5 seconds, outdoor motor will stop; if working current is less than 22A,
outdoor will resume to low speed (fan speed conversion frequency must be more than 45 seconds);
after compressor running for 5 minutes, if working current is more than 34A and keep it for 5
seconds, compressor will stop and will resume 3 minutes later.
If within 30 minutes there are 3 times compressor over current protection, compressor will not start
up, meanwhile, LCD will display E5. Only shut off and powered on again, the protection can be
cancelled.
4.3.2 Not in heating mode
After compressor running for 5 minutes, if working current is more than 34A and keep it for 5
seconds, compressor will stop and will resume 3 minutes later.
If within 30 minutes there are 3 times compressor over current protection, compressor will not start
up, meanwhile, LCD will display E5. Only shut off and powered on again, the protection can be
cancelled.
4.4 Power protection
4.5 High/Low Pressure protection (cooling only unit without this function)
After compressor running for 8 minutes, the system will check the pipe pressure. If pipe
pressure is over high, high pressure switch has acteivated more than 15 seconds, compressor,
outdoor motor will stop and 3 minutes later it will resume. If within 30 minutes there are stop
phenomenon 3 times because of pressure over high, the compressor will stop and LCD will display
E6. only shut off and powered on again, the protection can be cancelled.
Low pressure protection
(1) After compressor running for 3 minutes, if low pressure switch has acteivated for 15 seconds
continuously, compressor will stop and alarm.
(2) Check the low pressure switch when compressor is stop, the compressor will not run if low
pressure switch act, low pressure switch has acteivated more than 30 seconds, LCD will display
Low pressure abnormal
(3) In defrosting and in 6 minute after defrost is over , low pressure switch will not be checked.
(4) In heating, compressor run and outdoor motor stop, low pressure switch will be shielded.
(5) Low pressure protection can be resumable when power-off.
4.6 3-minutes protection for compressor
After compressor stops, it cannot be started until 3 minutes later. During the machine's running,
if the time not more than 3 minutes after power is off, the compressor cannot be restarted until 3
Electric control functions
-238-