TM 9-4120-357-14
b. Pressure-Test and Adjustment. Test and adjust regulator as directed in the following steps:
(1) Remove caps from the suction and discharge line service valves, and connect pressure gages to the gage
ports.
(2) Open both service valves.
(3) Replace front access panel on unit, leading gage lines out through circuit breaker access opening.
(4) Block off evaporator intake and fresh air intake to
cause suction pressure to
drop below normal.
(5) Provide temperature conditions of
50-75F (10-24 ) at
the condenser let, and start the air conditioner.
C
Turn the mode selector switch to cool, and the temperature control thermostat to maximum decrease.
(6) If suction line pressure gage reads higher or lower than the normal pressure 58 PSIG (4.08 KG/CM2) , remove
flat, knurled cap from pressure regulating valve (12, Figure 4-7) and adjust pressure regulating screws with a screw-
driver until 58 PSIG (4.08 KG/CM2) is obtained. Replace knurled cap.
(7) If pressure requirements cannot be met, close both system service valves, remove the pressure gages, and
replace the pressure regulating valve.
c Removal. Remove the pressure regulating valve from the air conditioner in accordance with the following proce-
dure:
(1) Discharging the System.
Whenever a
leak is
detected or a
refrigeration component must be
replaced, you
must discharge all gas from the refrigeration system in accordance with paragraph 5-6.
CAUTION
Wrap the valve body in wet cloth when brazing or debrazing joints. Excessive heat can
damage internal parts.
(2) Debrazing Connections. Provide a 1-2 CFM (0.5 - 1 M3) flow of dry nitrogen to the discharge line service
valve, and opening the cylinder shutoff valve and both service valves slightly. After the nitrogen has flowed through the
system for 2-3 minutes, debraze connections, and remove the pressure regulating valve.
d. Installation. Install a serviceable pressure regulating valve in the system, making sure that the direction of-flow
arrow is pointing in the proper direction. Establish a 1-2 CFM (0.5 - 1 M3) flow of dry nitrogen through the refrigeration
system, and braze the joints.
CAUTION
Whenever the refrigeration system has been opened to the atmosphere, you must install a
With the refrigeration system discharged and a hose attached to the gage port of the suction service valve, connect a
cylinder of oil-pumped dry nitrogen to the gage port of the high-pressure service valve. Open the high-pressure service
valve, and crack open the cylinder shutoff valve to establish a flow of 1-2 CFM (0.5 -1 M3) through the system. Purge
for at least 30 minutes to expel all other gases, impurities and water vapor. Turn off both service valves before discon-
necting the nitrogen cylinder and the discharge hose.
f. Charging the System. Prepare the refrigeration system for charging by attaching a pressure gage to the high pres-
sure service valve gage port, and a pressure hose and drier-strainer, loosely, to the suction service valve gage port.
Leave both valves closed. Proceed as follows:
CAUTION
Avoid contact with liquid refrigerant or escaping refrigerant gas. Irreversible tissue dam-
age can result from sudden freezing. Be especially careful to protect the eyes, avoid in-
haling high concentrations of refrigerant gas, and prevent gas coming into direct contact
with flame or hot metal surfaces; lethal phosgene gas can be formed.
(1) Connect a cylinder of refrigerant, R22, to the pressure hose. Open the cylinder shutoff valve slightly to purge the
hose of air, then tighten the hose connection to the suction service valve gage port.
5-33