Forced Defrost Operation; Preventing Compressor Overcurrent; The Protection Function Of Ac Current; Antifreezing Protection Of The Indoor Heat Exchanger - Haier 2U18MS2VHB Service Manual

Ductless multi-split heat pump, outdoor/indoor, wall mount - highwall, 2'x2' compact cassette, 3'x3' large cassette, slim duct, mid-static ducted, medium static ducted, console
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Forced Defrost Operation

There are times when the switch is not active. The periods of
inactive switch operation are:
1. When the compressor starts up the switch will be off for 8
minutes.
2. When the system is defrosting the switch is not active.
3. In the oil return cycles the switch is not active.
4. In the refrigerant discharging procedure after the oil return
in cooling is over the switch is not active.
The system will recognize cold evaporator temperatures as a
likely condition where the low pressure switch may open. The
ECU uses the Te sensor in heat mode and the Tc2 sensor in
·When unit stops, the reason that system still checks the low pressure : in a long time stop, make
cooling mode to monitor the temperature of the evaporator
protection for the compressor on the condition of great refrigerant leakage.
circuit. If abnormally cold coil temperatures are detected,
·The reason that low pressure switch action time is 30 seconds: when compressor stops, low pressure
does not change, so it will be shorter than the set time in operation.
the ECU will reduce the compressor operating frequency to
(3) When compressor starts up, in 8 minutes, low pressure switch signal will be shielded.
prevent potential low pressure switch trips. The charts below
(4) In defrosting, low pressu re switch will be shielded.
show the frequency versus evaporator circuit temperature
(5) In oil return procedure, low pressure switch will be shielded.
(6) In the refrigerant discharging procedure after the oil return in cooling is over, low pressure switch will
relationships.
be shielded.
In addition, the system will control low pressure through the evaporator temp. TE to realize the low
pressure protection function.
In cooling, confirm through Tc2AVE:
-13℉
-22℉
-31℉
-40℉
-49℉
In heating, confirm through defrosting temp. Te:
Te
-22℉
-31℉
-40℉
-49℉
-58℉

Preventing Compressor Overcurrent

If the failure is not confirmed as the permanent protec t ion, outdoor will not send failure code to indoor, and
indoor will not alarm.
During compressor start-up, if the current of the compressor
is greater than 17A for 3 seconds, the compressor will stop
and alarm. After 3 minutes, the compressor will restart. If this
occurs 3 times in 20 minutes the compressor will stop, lock
out, and display an error code. Power must be removed from
the system to clear the code.
During compressor start-up, if the AC current is greater than
12A, the frequency of the compressor decreases at the speed
of 1HZ/second.
During compressor start-up, if the AC current is greater than
10A, the frequency of the compressor decreases at the speed
of 0.1HZ/second.
B-14
Operations
Normal operation
Min. running FQY 20HZ
SV2 OFF & 20HZ
SV2 ON & 20HZ
Keep for 5 seconds, unit stops and alarm
occurs. 3 minutes later, restart up. If it
occurs 3 times in 1 hour, it will always
alarm and stop, electrify again and failure
will be cleared.
Normal operation
Min. running FQY 20HZ
SV2 OFF & 20HZ
SV2 ON & 20HZ
Keep for 5 seconds, unit stops and
alarm occurs. 3 minutes later, restart
up. If it occurs 3 times in 1 hour, it will
always alarm and stop, electrify again
and failure will be cleared.
72
OUTDOOR TECHNICAL OVERVIEW
During compressor start-up, if the AC current is greater
than 9A, the frequency of the compressor increases at the
prohibited speed.
During compressor start-up, if the AC current is greater than
8A, the frequency of the compressor increases at the speed
of no faster than 0.1HZ/second.

The Protection Function of AC Current:

• During the starting process of the compressor, if the AC
current is greater than 15A, the frequency of the
compressor decreases at the speed of 1HZ/second.
• During the starting process of the compressor, if the AC
current is greater than 13A, the frequency of the
compressor decreases at the speed of 0.1HZ/second.
• During the starting process of the compressor, if the AC
current is greater than 11A, the frequency of the
compressor increases at the prohibited speed.
• During the starting process of the compressor, if the
AC current is greater than 10A, the frequency of the
compressor increases at the speed of no faster than 0.1HZ/
second.
When the outdoor ambient temperature is high, there's
compensation for AC current protection.
When the outdoor ambient temperature is higher than 104°F,
AC current protection value decreases by 10AD
When the outdoor ambient temperature is higher than 115°F,
AC current protection value decreases by 15AD
When the outdoor ambient temperature is higher than 122°F,
AC current protection value decreases by 20AD

Antifreezing Protection of the Indoor Heat Exchanger

Prevents freeze-up of the indoor coil.
Outdoor coil
Outdoor coil
Heat Mode
Heat Mode
Temperature
Temperature
Sensor
Sensor
(Defrost)
(Defrost)

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