Refrigerant Circuit - CLIVET MSAN 81 Anleitung Zur Installation, Bedienung Und Wartung

REFRIGERANT CIRCUIT

- Correct compressor rotation direction
WARNING EXCESSIVE NOISE INDICATES THAT THE DIRECTION OF ROTATION IS NOT CORRECT
- Connect a pressure gauge suitable for high pressure to the corresponding Schrader fitting on the high pressure side of the
circuit, located at the high pressure switch.
- Check that the operation of the compressor leads to an increase in pressure on the high pressure side. No variation in
pressure means that the direction of rotation is not correct.
- Stop the compressor by operating the isolating switch.
- Reverse the connection of a pair of phase wires.
- Switch back the isolating switch, check the variation in pressure on the high pressure side, remove the pressure gauge.
- Carry out a final check for leaks from the valves and pressure test points on the system. Make sure that all the caps are
replaced on the test points and valves.
- Check liquid inspection opening (if present).
- Check the operating pressure using the pressure gauges connected (low pressure from 400KPa to 560Kpa, corresponding
to 0°C -+8°C SST), and condensing temperature of around 15-20°C greater than the outside air temperature (typical values).
- Check the superheating, by calculating the difference between the temperature read on the low pressure gauge, and the
temperature measured using a thermometer in direct contact with the inlet tubing upstream of the compressor. Values
between 4 and 8 degrees reflect correct operation, while in the event of values that differ greatly from these tolerances, refer
to the TROUBLESHOOTING section.
- Check the subcooling, by calculating the difference between the temperature read on the high pressure gauge, and the
temperature measured using a thermometer directly on the fluid line downstream of the condenser. Values of around 3/5
degrees mean correct operation, otherwise refer to the troubleshooting section as before.
- For correct analysis of the system, also check the compressor discharge temperature, which with the superheating and
subcooling data indicated must be around 30/40 degrees higher than the condensing temperature.
• It should be noted that the units feature fan speed control, and that it is useful to perform all these operating checks with
outside air - ambient air conditions similar to the standard design conditions.
It should also be noted that all the data indicated above is valid for units with a cooling field of operation.
For design conditions with an evaporation temperature (SST) lower than 0°C, check the operating parameters and the sizing of
the refrigerant pipes on a case-by-case basis.
For connection to terminal units fitted with fixed expansion devices, (for example, capillary tubing such as on our CED units for
false ceilings or CEI vertical flush-mounted units) the measurable parameters may change substantially according to the
operating conditions.
• This is due to the fact that while the thermostat controls the flow of refrigerant, in accordance with the inside/outside climatic
variations (maintaining the superheating of the gas constant), the presence of fixed expansion devices means that the system
balances by alternating movements of refrigerant on the high pressure side (condenser) or on the low pressure side
(evaporator), according to changes in the inside / outside climatic conditions.
IMPORTANT:
PAY SPECIAL ATTENTION TO THE COMPRESSOR DISCHARGE TEMPERATURE.
As a consequence, despite the refrigerant charge in the system being correct, the following operating conditions may occur:
- CHARGE CORRECT IF:
Rather high superheating (6/8°C) and subcooling (4/6°C) values, with the compressor discharge temperature 30/40°C above the
condensing temperature (values that indicate a concentration of refrigerant in the condenser, probably due to especially cold
outside air temperatures and/or rather hot inside air temperatures).
Rather low superheating (2/4°C) and subcooling (0/3°C) values, with the compressor discharge temperature 20/25°C above the
condensing temperature (values that indicate a rather cold inside temperature and/or hot outside temperature).
- CHARGE NOT CORRECT IF:
High superheating (6/8°C) and low subcooling (0/2°C) values, with the compressor discharge temperature 40/50°C above the
condensing temperature (values that indicate an insufficient refrigerant charge).
Low superheating values (0/2°C) and subcooling of 4/6°C, with compressor discharge temperature 15/20°C above the
condensing temperature (values that indicate an excessive refrigerant charge, with a probable return of liquid to the
compressor).
The above are some of the problems and corresponding solutions that may occur when starting a condensing unit; in any case,
the professionalism and qualification of the responsible personnel is essential.
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