Operating instructions

TM 11574A-OI
3-13
(4) Refrigeration Charge.
(a) Checking the refrigerant charge. To check the refrigeration charge, follow the steps
below:
NOTE
To avoid damage to the earth’s ozone layer, use a refrigerant recovery system whenever
removing refrigerant. When working with refrigerants you must comply with all local
government environmental laws. In the US, refer to EPA section 608.
1
Connect the gauge manifold to the compressor discharge and suction service valves.
2
Bring the container temperature to approximately 35 F (1.7 C) or 0 F (-17.8 C). Set
the controller set point to -13 F (-25 C) to ensure that the suction modulation valve is
at maximum allowed open position.
3
Partially block the condenser coil inlet air. Increase the area blocked until the
compressor discharge pressure is raised to approximately 175 psig @ (12 kg/cm@).
4
On units equipped with a receiver, the level should be between the glasses. If the
refrigerant level is not correct, continue with the following paragraphs to add or
remove refrigerant as required.
(b) Fully charging the refrigeration system. To fully recharge the refrigeration system, follow
the steps below:
1
Evacuate unit and leave in deep vacuum (refer to Evacuation and dehydration
paragraph 3-10b(3)).
2
Place cylinder of R-134a on scale and connect charging line from cylinder to liquid
line valve. Purge charging line at liquid line valve and then note weight of cylinder
and refrigerant.
3
Open liquid valve on cylinder. Open liquid line valve half-way and allow the liquid
refrigerant to flow into the unit until the correct weight of refrigerant (refer to
Refrigeration system data table paragraph) has been added as indicated by scales.
NOTE
It may be necessary to finish charging unit through suction service valve in gas form, due
to pressure rise in high side of the system (refer to Partial charging refrigeration system
section paragraph).
4
Open (backseat) manual liquid line valve (to close off gauge port). Close liquid valve
on cylinder.
5
Start unit in cooling mode. Run approximately 10 minutes and check the refrigerant
charge.
(c) Partial charging the refrigeration system. To partially recharge the refrigeration system,
follow the steps below:
1
Examine the unit refrigerant system for any evidence of leaks. Repair as necessary
(refer to Refrigerant leak checking paragraph).
2
Maintain the conditions outlined in Checking the refrigerant charge paragraph 3-
103b(4).