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8.5 LOW AMBIENT OPERATION
Even if the compressor can work in low ambient conditions, the system may require specific design or
recommendations to ensure compressor working conditions to remain inside the application envelop.
In the low ambient temperature, normally, the cooling load will be lower. To avoid the liquid flood back.
during the operation, the expansion device should be designed to maintain the minimum and stable
superheat. Short cycle of start/stop should be avoided, see Chapter
8.10 – Compressor On/off cycling.
The system should be verified by testing.
To prevent the flood start, a crankcase heater is required to avoid the compressor being the coldes point of
the installation. It has to be put in operation at minimum 12 hours before the first time start up. Despite the
radial compliance of our scroll compressors, the usage of a suction accumulator can be required, according
to the refrigerant charge of the system and refrigerant charge limits of the compressor see Chapter
8.8 –
Accumulator.
HP control pressure management like fan speed controller or regulating pressure switch for the condenser
fan is required to ensure the discharge pressure will never be lower than the minimum saturated condensing
temperature of the compressor envelop. And also maintain the enough pressure difference between the
discharge and suction pressure, to guarantee the right operation of the expansion device.
If the refrigerant is charged on the site, the adequate refrigerant quantity should be monitored by the scale
before start the compressor.
In case of ultra low ambient temperature; both the suction and discharge pressure inside the system
will be very low after a long time off period. When the compressor start up, because there is no enough
pressure difference between both sides of the expansion device, there will be no enough refrigerant to pass
the expansion device, the suction line pressure will be lower and the low pressure switch will cut off the
compressor running. In this case, because the pressure of the high side is also very low, it is impossible for
the suction pressure to arrive at the reset point of the low pressure switch, the compressor can't start again.
Some methods should be considered to maintain the pressure inside of the receiver during the long time off
period. Never short the circuit of the low pressure switch.
8.6 REFRIGERANT CHARGE
Avoid the liquid or gaseous refrigerants from vessel to come in contact with human
body. Skin, eyes may be permanently damaged; use personal safety equipment
(gloves, goggles).
Refrigerant charge amount depends from the internal volume of the system, its design and working conditions,
from the type of refrigerants and safety limits.
For each system, the optimal refrigerant charge should be determined by appropriate lab tests in order to
optimize the working conditions and energy consumption.
It is recommended to charge the system using the weighted charge method, using high side of the system.
Do not exceed the recommended charge limits or implement safety device (i.e.
suction accumulator). Never charge liquid to the low side at the start of the
charging procedure, refer to Chapter
11.6 - Charging process.
WARNING
CAUTION
