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Turn the unit ON using the ON-OFF button (or switch).
Press the MODE button to select COOLING OPERATION.
Press the MODE button again to select HEATING OPERATION (heat pump only).
The control system will enable the compressor to start after the pre-set safety times.
If the unit has more than one compressor, one will start after the pre-set safety times, and the others will start in sequence after the
first.
ELECTRICAL CHECKS
- Check the power supply voltage, as described previously.
CHECKING THE COMPRESSOR DISCHARGE TEMPERATURE
For a correct analysis of the system, also check the compressor discharge temperature, which at the indicated superheating and
subcooling values must be around 30/40 degrees higher than the condensing temperature.
- Check the power input of the compressor, referring to the electrical data table in the section on "Electrical connections".
- Check the power input of the fans, referring to the corresponding table in the section on "Electrical connections".
- Check the correct direction of rotation of the fans.
- Check, with the compressor off, the power input of the crankcase heaters (if present)
- After a short period of operation, check the oil level in each compressor (where the inspection glass is present) and the presence of
bubbles in the liquid line.
- Check the unit’s operating pressure in running conditions, using the pressure gauges connected
- The low pressure must stabilise at a value corresponding to a saturated temperature of around 4-6°C below the exchanger outlet
water temperature.
- The high pressure must stabilise at a value corresponding to a saturated temperature of around 15-20°C higher than exchanger coil
inlet air temperature.
These are typical values that are valid for standard operating conditions (flow-rate and water temperature, outside air temperature
near rated conditions).
N.B.: The saturated temperature is the temperature read on the pressure gauge corresponding to the pressure measured and the type
of refrigerant
REFRIGERANT CIRCUIT CHECKS
- Perform a final check for refrigerant leaks on the tap fittings and pressure test points in the system.
Start-up
WATER SYSTEM CHECKS
WATER FLOW-RATE:
- Check that the difference between the water inlet and evaporator outlet temperature is related to the capacity, according to the
formula :
refrigeration capacity (kW) x 860 = Dt (°C) x flow-rate ( L/h )
The reference Dt is of 5°C with unit at full load; differences higher than ±1°C must be considered very carefully.
The refrigeration capacity is defined in the tables on "Cooling Performance" in the TECHNICAL BULLETIN, according to:
- unit size
- condenser air inlet temperature
- evaporator fluid outlet temperature
N.B.
THE WATER FLOW-RATE AT THE EXCHANGER MUST REMAIN CONSTANT, IRRESPECTIVE OF THE THERMAL LOAD AND
THE UTILITIES CONNECTED
EVAPORATOR PRESSURE DROP:
Determine the water flow-rate, as follows:
Measure the existing pressure difference between the exchanger inlet and outlet, and calculate the flow-rate as shown under
the section "Water/aeraulic connections" in the graph "Exchanger/evaporator pressure drop, water side" (the working point
must not be off the graph).
The pressure can be measured more easily by installing the pressure gauges "M" shown in the same section on the water
connection diagram.
For units with built-in hydronic system (pump, expansion vessel, etc.), measure the existing pressure difference between unit inlet and
outlet and calculate the flow-rate value as shown under the section "Water/aeraulic connections" in the graph "Selecting the pump
based on the effective discharge head in the system".
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