Main Protection - Century B-VMH36SD-1 Service Manual

Service Manual - VMH 9/12/18/24 SU & VMH30/36S D Series

8.3 Main Protection

8.3.1 Three minutes delay at restart for
compressor
Less than one minute delay for the first time
start-up and a three minute delay for others.
8.3.2 Temperature protection of compressor
top
The unit will stop working when the compressor
top temp. protector cuts off, and will restart after
the compressor top temp. protector restarts.
8.3.3 Temperature protection of compressor
discharge
Compressor discharge temp. TP >115°F
(239°F) for 5s, compressor stops.
8.3.4 Fan speed is out of control
When Indoor fan speed runs too low
(300RPM) or too high (1500RPM) for a pre-
determined time, the unit will stop and the LED
will display the failure
8.3.5 Inverter module protection
The Inverter module has a protection function
for current, voltage and temperature. If these
protections happen, the corresponding code
will display on indoor unit and the unit will stop
working.
8.3.6 Indoor fan delayed open function
When the unit starts up, the louver will be active
immediately and the indoor fan will open 10
seconds later.
If the unit runs in heating mode, the indoor fan
will also be controlled by anti-cold wind
function. Fan will turn on, low speed, at 87°F
coil temperature. Fan will switch to high speed
at 114°F coil temperature.
8.3.7 Compressor preheating functions
Preheating permitting condition:
When T4 (outdoor ambient temperature) ＜3°C
(37.4°F), the preheating function will be
activated.
8.3.8 Zero crossing detection error
protection
If AC detects time interval is not correct for
continuous 240s, the unit will stop and the LED
will display the failure. The correct zero
crossing signal time interval should be between
6-13ms.
8.3.9 Sensor protection at open circuit and
breaking disconnection.
When there is only one temperature sensor in
malfunction, the air conditioner will keep
working but show the error code, in case of any
emergency use.
When there is more than one temperature
sensor in malfunction, the air conditioner will
stop working.
8.3.10 Refrigerant leakage detection
This function is only active in cooling mode. It
can better prevent the compressor being
damaged by refrigerant leakage or
compressor overload.
Open condition:
When compressor is active, the value of the
coil temperature of evaporator T2 has no
change, or very little change.
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