Operating instructions

TM 11574A-OI
3-6
b. Repair the Refrigeration System.
WARNING
Never use air for leak testing. It has been determined that pressurized mixtures of
refrigerant and air can undergo combustion when exposed to an ignition source.
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) Service Valves. The compressor suction, compressor discharge, and liquid line service
valves (Figure 3-2) are provided with a double seat and a gauge connection, which enable
servicing of the compressor and refrigerant lines. Turning the valve stem clockwise (all the
way forward) will front seat the valve to close off the suction, discharge or liquid line and open
the gauge port to the compressor or low side. Turning the stem counterclockwise (all the way
out) will open (backseat) the valve to open the connections and close off the port with the
valve stem midway between closed (front seat) and open (backseat), the lines are open to
both the connections and the gauge connection. For example, the valve stem is first fully
open (back seated) when connecting a manifold gauge to measure pressure. Then, the
valve is opened 1/4 to 1/2 turn to measure the pressure.
1. Suction, Discharge or
Liquid Line Connection
2. Service Port
3. Stem Cap
4. Valve Stem
5. Compressor Or Filter
Drier Inlet Connection
Figure 3-2. Service Valve.
(2) Manifold Gauge Set. The manifold gauge set is used to determine system operating
pressure, add refrigerant charge, and to equalize or evacuate the system.
When the suction pressure hand valve is front seated (turned all the way in), the suction (low)
pressure can be checked. When the discharge pressure hand valve is front seated, the
discharge (high) pressure can be checked. When both valves are open (turned counter-
clockwise all the way out), high pressure vapor will flow into the low side. When the suction
pressure valve is open and the discharge pressure valve shut, the system can be charged.
Oil can also be added to the system.