Carrier 69NT40-521, 69NT40-511-199 Suction and Discharge Service Valves, Pumping the Unit Down

6.2SUCTION AND DISCHARGE SERVICE VALVES

The suction and discharge service valves used on the compressor are equipped with mating flanges for connection to flanges on the compressor. These valves 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 frontseat the valve to close off the suction or discharge line and open the gauge connection to the compressor. See Figure 6-3. Turning the valve stem counterclockwise (all the way out) will backseat the valve to open the suction or discharge line to the compressor and close off the gauge connection.

With the valve stem midway between frontseated and backseated positions, the suction or discharge line is open to both the compressor and the gauge connection.

For example, when connecting a manifold gauge to measure suction or discharge pressure, the valve stem is fully backseated. Then, to measure suction or discharge pressure, crack open the valves 1/4 to 1/2 turn.

	Gauge Connection
To Suction or	Valve Cap
Discharge Line

	Valve Stem
Compressor
Valve	Valve
Frontseated	Backseated
(clockwise)	(counterclockwise)

Figure 6-3. Suction or Discharge Service Valve

6.3 PUMPING THE UNIT DOWN

To service the filter-drier, moisture-liquid indicator, expansion valve, suction modulation valve, suction solenoid valve or evaporator coil, pump most of the refrigerant into the condenser coil and receiver as follows:

a.Backseat the suction and discharge valves (turn counterclockwise) to close off gauge connections and attach manifold gauges to valves.

Refer to section 6.1.a.

b.Allow the compressor to run 10 to 15 minutes before frontseating the liquid line valve. Then close (front seat) the liquid line valve by turning

clockwise. Start the unit and run in a cooling mode. Place start-stop switch in the OFF position when the unit reaches a positive pressure of 0.1 kg/cm@ (1.0 psig).

c.Frontseat (close) the suction service valve. The refrigerant will be trapped between the compressor suction service valve and the liquid line valve.

d.Before opening up any part of the system, a slight positive pressure should be indicated on the pressure gauge. If a vacuum is indicated, emit refrigerant by cracking the liquid line valve momentarily to build up a slight positive pressure.

e.When opening up the refrigerant system, certain parts may frost. Allow the part to warm to ambient temperature before dismantling. This avoids internal condensation which puts moisture in the system.

f.After repairs have been made, be sure to perform a refrigerant leak check (section 6.4), and evacuate and dehydrate the system (section 6.5).

g.Check refrigerant charge (refer to section 6.6).

6.4 REFRIGERANT LEAK CHECKING

WARNING

Never mix refrigerants with air for leak testing. It has been determined that pressurized, air-rich mixtures of refrigerants and air can undergo combustion when exposed to an ignition source.

a.The recommended procedure for finding leaks in a system is with a R-134a electronic leak detector. Testing joints with soapsuds is satisfactory only for locating large leaks.

b.If the system is without refrigerant, charge the system with refrigerant to build up pressure between 2.1 to 3.5 kg/cm@ (30 to 50 psig). Remove refrigerant cylinder and leak-check all connections.

NOTE

It must be emphasized that only the correct refrigerant cylinder be connected to pressurize the system. Any other gas or vapor will contaminate the system, which will require additional purging and evacuation of the system.

c.Remove refrigerant using a refrigerant recovery system and repair any leaks.

T-268-07 6-4