Accurater™ (Bypass-Type) Heat Pumps Only - Carrier R-22 Application Manual And Service Manual

STEM
SEAT
FORGED FRONT SEATING VALVE
pressurized. To pressurize the service port, this valve must be
moved off the back-seating position. This valve does not contain a
Schrader fitting. Both types of service valves are designed for
sweat connection to the field tubing.
The service valves in the outdoor unit come from the factory
front-seated. This means that the refrigerant charge is isolated from
the line-set connection ports. Some heat pumps are shipped with
sweat-adapter tube. This tube must be installed on the liquid-
service valve. After connecting the sweat adapter to the liquid-
service valve of a heat pump, the valves are ready for brazing. The
interconnecting tubing (line set) can be brazed to the service valves
using either silver-bearing or non-silver-bearing brazing material.
Consult local codes.
Before brazing the line set to the valves, the belled ends of the
sweat connections on the service valves must be cleaned so that no
brass plating remains on either the inside or outside of the bell
joint. To prevent damage to the valve and/or cap O ring, use a
wet cloth or other acceptable heat-sinking material on the valve
before brazing. To prevent damage to the unit, use a metal barrier
between brazing area and unit.
After the brazing operation and the refrigerant tubing and evapo-
rator coil have been evacuated, the valve stem can be turned
counterclockwise until it opens or back-seats, which releases
refrigerant into tubing and evaporator coil. The system can now be
operated.
Back-seating service valves must be back-seated (turned counter-
clockwise until seated) before the service-port caps can be re-
moved and hoses of gage manifold connected. In this position,
refrigerant has access from and through outdoor and indoor unit.
The service valve-stem cap is tightened to 20 ± 2 ft/lb torque and
the service-port caps to 9 ± 2 ft/lb torque. The seating surface of
the valve stem has a knife-set edge against which the caps are
tightened to attain a metal-to-metal seal. If accessory pressure
switches are used, the service valve must be cracked. Then, the
knife-set stem cap becomes the primary seal.
SERVICE PORT
W/SCHRADER
CORE
FIELD
SIDE
A91448
Fig. 46—Service Valves
FIELD
SIDE
SEAT
BAR STOCK FRONT SEATING VALVE
The service valve cannot be field repaired; therefore, only a
complete valve or valve stem and service-port caps are available
for replacement.
If the service valve is to be replaced, a metal barrier must be
inserted between the valve and the unit to prevent damaging the
unit exterior from the heat of the brazing operations.
Wear safety glasses and gloves when handling refrigerants.
Pumpdown Procedure
Service valves provide a convenient shutoff valve useful for
certain refrigeration-system repairs. System may be pumped down
to make repairs on low side without losing complete refrigerant
charge.
1. Attach pressure gage to suction service-valve gage port.
2. Front seat liquid-line valve.
3. Start unit in cooling mode. Run until suction pressure reaches
5 psig (35kPa). Do not allow compressor to pump to a
vacuum.
4. Shut unit off. Front seat suction valve.
NOTE: All outdoor unit coils will hold only factory-supplied
amount of refrigerant. Excess refrigerant, such as in long-line
applications, may cause unit to relieve pressure through internal
pressure-relief valve (indicated by sudden rise of suction pressure)
before suction pressure reaches 5 psig (35kPa). If this occurs, shut
off unit immediately, front seat suction valve, and recover remain-
ing pressure.
Step 5—AccuRater™ (Bypass-Type) Heat Pumps Only
AccuRater™ piston has a refrigerant-metering hole through it. The
retainer forms a stop for piston in refrigerant-bypass mode and a
sealing surface for liquid-line flare connection. (See Fig. 47). To
check, clean, or replace piston:
40
STEM
SERVICE PORT
W/SCHRADER CORE
A91447