MSAT 102-122-142-162-182-202-242

START-UP
- Make sure the indoor unit is working correctly.
- Check the connections of any solenoid valves.
- Locate the command SA2 on the wiring diagram. This represents the signal from the indoor unit for the selection of the
capacity-control step, and corresponds to the activation of the first step, while the command for the activation of the
second step is represented by the symbol SA3 on the wiring diagram .
- The first compressor to start is defined by the control system (see control manual).
The fans in the circuit in operation only start at the same time as the compressor.
- Make sure that there is demand from the system.
- To add refrigerant gas, use the service test point on on-off valve in the suction line, and introduce freon in the gaseous
state. Pay careful attention in this phase, as during start-up the minimum pressure switch is bypassed for 70 seconds.
To charge one circuit first and then the other, use the corresponding fuse holders to stop the compressor on the circuit
not being charged, as the control module features an operating cycle logic.
IMPORTANT: after stopping, the system counts a period of 6 minutes from the previous start, (if this time has already
elapsed only the 30 second delay will be counted) before starting again.
- The charge is considered complete when:
- No bubbles can be seen in the liquid inspection opening (if present).
- The superheating of the suction gas is 4-8°K.
- The subcooling of the liquid is 3-5°K.
ADDING OIL
The exact quantity of refrigerant added to the system, in addition to the factory charge, must be known in order to define
the quantity of oil required. The quantity must be equal to around 10% of the weight of the refrigerant added (the type of
oil is specified in the general manual). Oil must be added for refrigerant top-ups of over 3kg. In any case, check the
compressor oil level using the Schrader fitting, where present.
CHECKS ON FIRST START-UP
AFTER HAVING STARTED THE UNIT, CHECK:
ELECTRICAL PARTS
The unbalance of the phases. This must be lower than a maximum value of 2% (see calculation example).
Calculation example:
L1 - L2 = 388V L2 - L3 = 379V L3 - L1 = 377V
The average of the values measured is:
388 + 379 + 377
= 381
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The maximum deviation from the average is:
388-381=7 V
The unbalance is therefore:
7
x 100 =1,83% (acceptable)
381
Compressor power input. Must be less than the value shown in the table enclosed, under the item F.L.A.
REFRIGERANT CIRCUIT
- 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 and fitted with
thermostats.
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.
- The indications provided above are some of the problems and corresponding solutions that may arise when the condensing
unit is started; the professionalism and qualification of the personnel responsible are in any case essential.
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