Service Manual

23
tube. This tube must be installed on the liquid service valve.
After connecting the stub tube 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 industry accepted methods and
materials. 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
evaporator coil have been evacuated, the valve stem can
be turned counterclockwise until 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
counterclockwise until seated) before the service- port caps
can be removed and hoses of gauge 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.
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.
PERSONAL INJURY HAZARD
Failure to follow this caution may result in personal
injury.
Wear safety glasses, protective clothing, and gloves
when handling refrigerant.
CAUTION
!
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 gauge to suction service- valve
gauge 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.
STEM
SERVICE PORT
W/SCHRADER CORE
SEAT
BAR STOCK FRONT SEATING VALVE
FIELD
SIDE
A91447
Fig. 15 – Suction Service Valve (Front Seating)
Used in Base and Comfort ACs and HPs
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 unit off immediately, front
seat suction valve, and recover remaining pressure.
Heating Piston (AccuRater
r) - Heat Pumps Only
In most heat pumps, AccuRater pistons are used to meter
refrigerant for heat pump heating mode only. All indoor coils
are supplied with a bi- flow TXV for metering in the cooling
mode. AccuRaterr piston has a refrigerant metering hole
through it. The piston seats against the piston body in
heating mode and meters the refrigerant in heating mode
and allows refrigerant to flow around it in cooling mode.
There are 2 types of liquid line connections used. Flare
connections are used in R- 22 systems.
1. Shut off power to unit.
2. Pump unit down using pumpdown procedure
described in this service manual.
3. Loosen nut and remove liquid line flare connection
from AccuRaterr.
4. Pull retainer out of body, being careful not to scratch
flare sealing surface. If retainer does not pull out
easily, carefully use locking pliers to remove it.
5. Slide piston and piston ring out by inserting a small
soft wire with small kinks through metering hole. Do
not damage metering hole, sealing surface around
piston cones, or fluted portion of piston.
6. Clean piston refrigerant metering hole.
7. Install a new retainer O- ring, retainer assembly, or
Teflon washer before reassembling AccuRaterr.