7--2
T--311
g. Repeat steps d.and e. one time.
h. Evacuate unit to 500 microns. Close the electronic
vacuum gauge and vacuum pump valves. Shut off the
vacuum pump. Wait five minutes to see if vacuum
holds. This procedure checks for residual moisture
and/or leaks.
i. With a vacuum still in the unit, the refrigerant charge
may be drawn into the system from a refrigerant con-
tainer on weight scales.
7.3 INSTALLING MANIFOLD GAUGES
The manifold gauge set is used to determine system
operating pressures, add refrigerant charge, and to
equalize or evacuate the system.
When the suction pressure hand valve is frontseated
(turned all the way in), the suction (low) pressure can be
checked. When the discharge pressure hand valve is
frontseated, 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.
A R-134a manifold gauge/hose set with self-sealing
hoses is required for service of the models covered
within this manual. The manifold gauge/hose set is
available from Carrier Transicold. (Carrier Transicold
P/N 07-00294-00, which includes items 1 through 6. To
perform service using the manifold gage/hose set, do
the following:
a.
Preparing Manifold Gauge/Hose Set For Use
1. If the manifold gauge/hose set is new or was
exposed to the atmosphere it will need to be eva-
cuated to remove contaminants and air as follows:
2. Back seat (turn counterclockwise ) both field service
couplings (see Figure 7-1) and midseat both hand
valves.
3. Connect the yellow hose to a vacuum pump.
4. Evacuate to 10 inches of vacuum.
5 Connect yellow line to R134a cylinder, purge line,
then charge with to a slightly positive pressure of 0.1
kg/cm
@
(1.0 psig).
6. Front seat both manifold gauge set valves and dis-
connect from cylinder. The gauge set is now ready
for use.
b.
Connecting Manifold Gauge/Hose Set
Connection of the manifold gauge/hose set (see
Figure 7-2) is dependent on the type system being
serviced. The center hose connection is brought to the
tool being used. To connect the manifold gauge/hose
set, do the following.
1. Connect the high side field service coupling to the
discharge line service valve port.
2. Turn the high side field service coupling knob (red)
clockwise, which will open the high side of the sys-
tem to the gauge set.
3. Connect the low side field service coupling to the
suction service valve port.
4. Turn the low side field service coupling knob (blue)
clockwise, which will open the low side of the system
to the gauge set.
CAUTION
To prevent trapping liquid refrigerant in the
manifold gauge set be sure set is brought to
suction pressure before disconnecting.
OPENED
(Backseated )
HAND VALVE
CLOSED
(Frontseated)
HAND VALVE
SUCTION
PRESSURE
GAUGE
DISCHARGE
PRESSURE
GAUGE
To Low Side
Access Valve
To High Side
Access Valve
Red Knob
Blue Knob
1
4
3
YELLOW
2
4
5
6
3
RED
3
BLUE
2
1. Manifold Gauge Set
2. Hose Fitting (0.5-16 Acme)
3. Refrigeration and/or Evacuation Hose
.
(SAE J2196/R-134a)
4. Hose Fitting w/O-ring (M14 x 1.5)
5. High Side Field Service Coupling
6. Low Side Field Service Coupling
Figure 7-1 Manifold Gauge Set
c.
Removing the Manifold Gauge Set
1. Midseat both hand valves on the manifold gauge set
and allow the pressure in the manifold gauge set to
be drawn down to suction pressure. This returns any
liquid that may be in the high side hose to the system.
2. Backseat both field service couplings and frontseat
both manifold set valves. Remove the couplings
from the service ports.
3. Install both service port caps (finger-tight only).