Defrost Control; Defrosting Beginning Conditions; Defrosting Finish Conditions; Protection During Defrost - Haier H-MRV Series Service Manual

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If Ta ≤27℃, when compressor stops, electric heater is electrified on.
When Ta ≥32℃, or compressor starts up, electric heater is not electrified.

6. Defrost control

In heating mode, the defrosting sensor Te will check the frost state of outdoor heat exchanger, to
control defrosting function.

6.1 Defrosting beginning conditions

In heating mode, if the compressor has run for 45 minutes in all, by checking the defrosting sensor
Te and outdoor ambient temperature sensor Ta, the unit will enter defrost operation:
When Ta ＜2℃, if for 2 minutes contineously Ta-Te≥9℃, or for 5 minutes contineously Te＜12℃,
the unit will enter defrost.
When Ta ≥2℃, if for 5 minutes contineously Te＜-5℃, the unit will enter defrost.

6.2 Defrosting finish conditions

The defrost operation will be over 10 minutes later after defrost begins.
By checking the outdoor defrosting state through Te, if Te is over 7℃ for over 60 seconds in all or
Te reaches 12℃, defrost will finish.

6.3 Protection during defrost

A: Pressure switch not work
B: Protection to temperature sensors is cancelled
6.4 Measures after defrosting: If the defrost is over, the adjustment of the solenoid valve and the
current can be treated as the adjustment when compressor starts up.
7. Control of refrigerant spray valve SV2
Control of refrigerant spray: according to the overheat state of compressor discharging, the unit will
control the open time of SV2.
7.1 Control conditions
A. In cool/heat/dry mode, SV2 can be controlled.
B. Within soft startup period (3 minutes) after compressor starts up, the abnormal suction temp.,
discharging temp. of compressor will be ignored.
7.2 After compressor starts up for 3 minutes, according to the overheat state of compressor
discharging, perform as follow:
If the discharging temp. is overhigh, the spray valve will open; while overlow, it will close.
8. Unloading valve SV1
According to the operation state, the open/close control of unloading valve will be as follow:
Unloading valve SV1: Before or after compressor starts up, it will make unloading operation.
In the compressor soft startup period, SV1 opens; after soft startup is over, SV1 closes.
If compressor shuts off, SV1 opens and will delay 10 minutes to close.
In heating, Ta ＞17℃, and running indoor HP ≤1HP, SV1 will open or close according to the
discharging temp. and the coil temp.
9. Discharging temperature sensor Td
Within 3 minutes after compressor begins soft startup or the unit receives the stop-compressor
signal, the abnormal value of Td, Ts will be ignored.
Due to the measured temperature by Td and Ts, the unit will make by-pass control when the
discharging temperature is overheat.
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