TM 9-4120-357-14
h. Final Assembly. Replace the front access panel on the air conditioner by placing the bottom edge behind the
step in the base plate, then pushing into position. Secure with four panel fastener screws.
5-23. Service Valves.
The suction line service valve and the discharge service valve are identical, and are located in the front center area of
the lower compartment. (See Figure 1-2.) The service valves are used for charging and discharging refrigerant into or
out of the system.
a. Access. Obtain access to the service valves by removing the front access panel as follows:
(1) Unscrew four panel fastener screws securing the front access panel.
(2) Pull the panel forward and upward to remove.
b. Discharging the System.
Whenever a
leak is
detected or a
refrigeration component must be
replaced, discharge
all gas from the refrigeration system in accordance with paragraph 5-6.
CAUTION
Wrap the body of the valve to be brazed or debrazed; in wet cloth. Excessive heat can
damage internal parts.
c. Removal. Connect a cylinder of dry nitrogen to whichever of the service valves is not to be removed, and estab-
lish a 1-2 CFM (0.5-1 M3) flow through the system for 3-5 minutes. Debraze joint of valve to be removed, and remove
valve.
d. Installation. With nitrogen flowing through the system, set the service valve in place and braze the joint.
CAUTION
Whenever the refrigeration system has been opened to the atmosphere, you must install
With the refrigeration system discharged and a hose attached to the gauge port of the suction service valve, connect a
cylinder of oil-pumped dry nitrogen to the gauge 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 M ) 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-
pressure service valve gage port, and pressure hose and drier-strainer, loosely, to the suction service valve gage port.
Leave both valves closed. Proceed as follows:
WARNING
Avoid contact with the liquid refrigerant or escaping refrigerant gas. Irreversible tissue
damage can result from sudden freezing. Be especially careful to protect the eyes. Avoid
inhaling high concentrations of refrigerant and prevent gas coming into direct contact
with flame or hot metal surfaces; lethal phosgene gas can be formed.
(1) Connect a cylinder or 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.
(2) Open both service valves and the cylinder shutoff valve, and charge the system with refrigerant gas until the gage
on the discharge (high-pressure) service valve registers 70 (5KG/ CM2) . Close the suction service valve and the cylin-
der shutoff valve.
(3) Transfer the charging line to a
cylinder of
dry nitrogen. Open the cylinder shutoff valve and suction service valve,
and let nitrogen flow into the refrigeration system until the discharge pressure gage reads 350 PSI (21.44 KG/CM2) .
Turn off suction and discharge service valves and the cylinder shutoff valve. Disconnect the charging line from the suc-
tion service valve.
5-42