T-CU11-OCT22-0
Page 15
Installation
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 indication tag which is tied to service valve before installation.
Once the pipework installation is complete, it should be pressure tested for leaks prior to evacuation.
A pressure leak test should be carried out using oxygen free nitrogen (OFN). 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 PPE as required.
Leak detection must be carried out using oxygen free nitrogen (OFN), or a mixture of
nitrogen and refrigerant or nitrogen and helium. Never use other gasses such as
oxygen, dry air or acetylene as these may form an inflammable mixture.
Always pressurize the system on high pressure side first then only low-pressure side, preferably in stages up to the
maximum required pressure. Never exceed maximum test pressures shown in
Failure to obey the limit will
cause premature failure on the pressure safety device.
Listen for any possible leaks and check all joints with bubble spray. If any leaks are discovered, release pressure slowly
from both high pressure and low-pressure side 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 installed pipework only) according to applicable standards.
Once testing has been completed satisfactorily, release the pressure from the system gradually and safely to external
atmosphere.
Table 7: Maximum Test Pressures
High Side, barG/ psig
Low Side, barG/psig
28/405
19/275
Evacuation
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) measured at refrigeration system, and not at the vacuum pump
gauge.
Once pressure testing has been completed, the system can now be evacuated to remove air and any moisture from the
piping. It is recommended to evacuate on both high- and low-pressure side to achieve fast and uniform vacuum in the
entire system. 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.
