T-CU19-JAN24-1
Page 12
Figure 8: Piping layout for outdoor below
indoor
Pressure Testing
•
The condensing units are pressure tested in the factory
prior to dispatch. All units come with a holding charge
of oxygen free nitrogen. Remove the holding charge
and indication tag prior to pipework installation using
the service valve or regulator with pressure gauges
and hoses.
•
Once the pipework installation is complete, it should be
pressure tested prior to evacuation to test for leaks.
•
A pressure leak test should be carried out using
oxygen free nitrogen (OFN). NEVER USE OXYGEN
FOR PRESSURE TESTING SYSTEMS. A calibrated
nitrogen pressure regulator must always be used.
Before starting any pressure testing, ensure the area
surrounding the system is safe, inform relevant
personnel and fit warning signs indicating high pressure
testing. Also, use correct Personal Protection Equipment
(PPE) as required.
•
Always pressurize the system slowly, preferably in
stages up to the maximum required pressure. Maximum
test pressures applicable to the unit are as follows:
Table 9: Test Pressure
Test Pressure (barg/psig)
High side
Low side
28/405
19/275
•
Listen for any possible leaks and check all joints with
bubble spray. If any leaks are discovered, release
pressure slowly from system until empty, repair leak
and then restart pressure testing procedure. Never
attempt to repair a leak on a pressurized system.
•
A strength test should also be incorporated (to install
pipework only) according to applicable standards.
•
Once testing has been completed satisfactorily, release
the pressure from the system gradually and safely to
external atmosphere.
Evacuation and Charging
Moisture prevents proper functioning of the
compressor and the refrigeration system.
Ensure that a good quality vacuum pump is
used to pull a minimum vacuum of 250
microns (0.25 torr).
Once pressure testing has been completed, the system can
now be evacuated to remove air and any moisture from the
piping. This can be done as follows:
•
Ensure any nitrogen charge is safely released from the
system.
•
Connect a gauge manifold to the connections on the
service valves on the condensing unit.
•
Connect a vacuum pump and vacuum gauge to the
system.
•
Ensure all gauge manifold and service valves are open
as required.
•
Evacuate the system until vacuum is below 250 microns
(0.25 torr).
Note: A triple evacuation procedure is recommended for all
new systems or where moisture is suspected.
•
Once the system is isolated and the vacuum pump is
switched off, any rise in pressure indicates that either
there may be a leak in the system or moisture is still
present. In this case, recheck the system for leaks,
repair as necessary, and then restart the evacuation
procedure. Once completed satisfactorily, the vacuum
pump and vacuum gauge can be removed.
•
At this point, the refrigerant charge can be added to
the system as required. Refrigerants must be charged
in the liquid phase. Charging liquid into the suction side
of the system should ONLY be done with a metering
device. Use calibrated weighing scales to record the
amount of refrigerant added to the system.
OUTDOOR
UNIT
INDOOR
UNIT
INVERTED P-TRAP
SUCTION LINE
LIQUID LINE
MAX. RISE 6M
2cm/m SLOPE, 4m/s OR MORE
BULB LOCATION
