g. Start-up & Operation
Initial pressure test (by vacuum and nitrogen) - Step-by-step:
-
Use a 4-port gauge manifold with 3/8” hose and connections to the vacuum
pump. The vacuum gauge does not have to be connected for this part of the
process.
-
Connect the gauges to service ports provided on receiver valve and suction
tube. In order to remove any non-condensable that may have entered the
system during installation, follow these steps:
-
Start the vacuum pump. The evaporator fan should be running and the
compressor crankcase heater is energized at this point. This will involve
powering up the unit so it is important to disconnect the live feed wire to the
compressor contactor (so the compressor cannot run and the crankcase
heater can be energized).
-
Open both valves on the manifold and then open the main vacuum valve on
the pump. Run the system until the vacuum level of -0.85 bar (as read on
manifold gauge) is achieved.
-
Shut off the main vacuum pump valve. Check for vacuum rise using the
manifold compound gauge. A rise would indicate a large leak.
-
If vacuum holds for 10 minutes, break vacuum with Nitrogen. Check the
name plate of the unit / compressor for allowable leak test pressure. Ensure
that pressure regulators are installed on the Nitrogen cylinders. Check for
leaks and repair leakage.
Leak Check
The success of all the subsequent commissioning depends on a leak free system,
free of contaminants, free of oxides, free of non-condensable’ s, that has been evac-
uated to a low vacuum and charged with the prescribed refrigerant.
Leak test is particularly important for field-connected systems. Typically, field
systems lose as much as 20%–30% of their refrigeration charge annually. This is not
only an unnecessary expense but also damages the environment. Compressor oil
can be lost at the same time as refrigerant and eventually lead to compressor
failure. (Time spent on leak test will eventually reduce the time spent on the evacua-
tion process).
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