Installing Manifold Gauges; Installing R-134A Manifold Guage Set; Pumping The System Down Or Removing The Refrigerant Charge; System Pumpdown - Carrier 68G5-105 Series Operation & Service Manual

4.3 INSTALLING MANIFOLD GAUGES

The manifold gauge set can be used to determine
system operating pressures, add charge, equalize or
evacuate the system.
Low Pressure
Gauge
Opened
(Backseated )
Hand Valve
To Low Side
Access Valve
3
BLUE
2
4
6
(Blue Knob)
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 Coupler
6. Low Side Field Service Coupler
Figure 4-2. Manifold Gauge Set (R-134a)
4.3.1 Installing R-134a Manifold Gauge Set
An R-134a manifold gauge/hose set with self-sealing
hoses is required for service of models covered within
this manual. The manifold gauge/hose set is available
from Carrier Transicold. (CTD P/N 07-00294-00, which
includes items 1 through 6, see Figure 4-2.) To perform
service using the manifold gauge/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
evacuated to remove contaminants and air as
follows:
2. Back seat (turn counterclockwise ) both field service
couplers (See Figure 4-2, items 5 and 6) and
midseat both hand valves.
3. Connect the yellow hose to a vacuum pump and an
R-134a cylinder.
4. Evacuate to 10 inches (0.69 BAR) of vacuum and
then charge with R-134a to a slightly positive
pressure of 1.0 psig (0.07 BAR).
T-312
High Pressure
1
Gauge
Closed
(Frontseated)
Hand Valve
2
To High Side
Access Valve
3
RED
3
YELLOW
4
5
(Red Knob)
5. Front seat both manifold gauge set hand valves and
disconnect from cylinder. The gauge set is now
ready for use.
b. Connecting Manifold Gauge/Hose Set
To connect the manifold gauge/hose set for reading
pressures, do the following:
1. Remove service valve stem cap and check to make
sure it is backseated. Remove access valve cap.
2. Connect the field service coupler (see Figure 4-2,
items 5 and 6) to the access valve.
3. Turn the field service coupling knob clockwise, which
will open the system to the gauge set.
4. Read system pressures.
5. Repeat the procedure to connect the other side of
the gauge set.
c. Removing the Manifold Gauge Set
1. While the compressor is still ON, backseat the high
side service valve.
2. Midseat both hand valves on the manifold gauge set
and allow the pressure in the manifold gauge set to
be drawn down to low side pressure. This returns
any liquid that may be in the high side hose to the
system.
To prevent trapping liquid refrigerant in
the manifold gauge set be sure set is
brought to suction pressure before
disconnecting.
3. Backseat the low side service valve. Backseat both
field service couplers and frontseat both manifold set
hand valves. Remove the couplers from the access
valves.
4. Install both service valve stem caps and access
valve caps (finger-tight only).
4.4 PUMPING THE SYSTEM DOWN OR

REMOVING THE REFRIGERANT CHARGE

To avoid damage to the earth's ozone layer,
use a refrigerant recovery system whenever
removing refrigerant.

4.4.1 System Pumpdown

To service or replace the filter-drier, expansion valve,
evaporator coil, or suction line, pump the refrigerant into
condenser coil as follows:
a. Install manifold gauge set. (Refer to paragraph 4.3)
b. Start the unit and allow it to run in the cool mode for 15
to 20 minutes.
c. Unplug the suction pressure transducer(SPT).
The following procedure may have to be
repeated several times to maintain the 0 to 2
psig (6.9 kPa) pressure depending upon
amount of refrigerant absorbed in the oil.
4-2
CAUTION
NOTE
NOTE