Regulation; Calibration Of General High Pressure Switch (Srmcr) - Arneg UCA Manuel D'installation Et De Service

- If the system still contains water and is not sealed, the curve will be similar to the previous one but after dropping the
pressure will continue to rise.
In both cases the operation should be repeated and, in the second case, the leaks should be eliminated first.
If the system is perfectly sealed and correctly dehydrated, the pressure ascent curve acquires a characteristic flat profile
and the pressure increase in 24 hours will not exceed 0.5 mbar
The admissible extent of the pressure increase, that is, 0.5 mbar as indicated above, should not be placed in relation to
the volume of the system: it is a mistake to think that an increase of more than 0.5 mbar is tolerable in a large system
over a period of 24 hours.
Filling with coolant
Before filling with coolant, make sure:
- The vacuum is as required above
- The compressors are working properly
- All safety devices have been calibrated at the nominal values
- There is the required amount of oil (top up if necessary before applying the vacuum)
- The condenser fans function normally and rotate in the proper direction.
Since at the present time the European directive and Italian law only permit use of mixtures of HFC as coolants, these
specifications will only refer to their use.
a) The system should be filled with coolant in the liquid state without starting the compressors until the pressure of
the system and tank is balanced. When filling with coolant on the intake side, make sure there is not too much foam
or coolant on the compressor because this could cause mechanical damage.
To start the machine use the circuit breaker on the power panel and wait for the electronic circuit to complete its
calculations.
4.2

REGULATION

The parts requiring calibration are:
4.2.1) The pressure switch
4.2.2) The bimetal relay (also called thermal relay)
4.2.3) Where required, the pressure limiting valve on the casing (also called KVL)

CALIBRATION OF GENERAL HIGH PRESSURE SWITCH (SRMCR)

Devices designed to prevent pressure equipment from exceeding the admissible limits are called "Safety Accessories".
Directive 97/23/CE (European Directive for Pressure Equipment "P.E.D.") describes two types of safety devices.
- devices for direct pressure limitation, such as safety valves, bursting disk safety devices, buckling rods,
controlled safety pressure relief systems (CSPRS), and
- limiting devices, which either activate the means for correction or provide for shutdown or shutdown and
lockout, such as pressure switches or temperature switches or fluid level switches and 'safety related
measurement control and regulation (SRMCR) devices.
The Pressure switches used by ARNEG SPA and considered as (SRMCR), are classified in category IV of the above
directive and are used only for safety in the high pressure side.
On mono or multi compressor refrigerating units (GFMMC) other types of pressure switches may be found, used for
control of the assembly. These pressure switches can be connected either in the system or in the GFMMC. The
calibration depends on the working conditions considered most appropriate for the system. The PED classification of
these pressure switches depends on their maximum admissible pressure and their DN.
REGULATION OF SRMCR (SAFETY Pressure switch):
CODE: 05050532 Edition 02 15-04-2003
05050532 03 11/02/2010
Use and Maintenance of Condensing Units
Technical Manual
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