Thermostatic-Expansion Valves (Txv) - Carrier R-22 Application Manual And Service Manual

4TH PORT
4 PORT DESIGN
4. Braze new valve onto used stubs. Keep stubs oriented cor-
rectly. Scratch corresponding matching marks on old valve
and stubs and on new valve body to aid in lining up new valve
properly. When brazing stubs into valve, protect valve body
with wet rag to prevent overheating.
5. Use slip couplings to install new valve with stubs back into
system. Even if stubs are long, wrap valve with a wet rag to
prevent overheating.
6. After valve is brazed in, check for leaks. Evacuate and charge
system. Operate system in both modes several times to be sure
valve functions properly.
Step 7—Thermostatic-Expansion Valves (TXV)
TO OUTDOOR
COIL
TP-4
FROM COMPRESSOR
DISCHARGE LINE
Fig. 49—Reversing Valve (Cooling Mode or Defrost
Mode, Solenoid Energized)
The types of TXVs used in condensing-unit and heat-pump
systems are as follows:
Rapid-Pressure Balance (RPB)—Has a special bleed port that
NEW SOLENOID COIL
Fig. 48—Reversing Valve
FROM INDOOR COIL VIA
SERVICE VALVE ON
OUTDOOR COIL
TO
ACCUMULATOR
TP-3 TP-2
TP-1
A88342
A91456
FROM
OUTDOOR
COIL
TP-4
INSULATE FOR
ACCURATE
READING
FROM COMPRESSOR
DISCHARGE LINE
Fig. 50—Reversing Valve (Heating Mode, Solenoid
allows rapid bleed-through of pressure after system shutdown until
pressure equalization occurs within approximately 1 to 2 minutes.
Hard Shutoff (HSO)—Has no bleed port and allows no bleed-
through after system shutdown. No pressure equalization occurs.
Because of unequalized system pressures, a start capacitor and
relay must be installed on single-phase reciprocating compressors
to start the compressor.
See Table 21 for TXV superheat settings. These settings are
factory-set and are not field adjustable. Table 21 settings are for
Carrier-approved accessories and factory-installed TXVs only.
42
3 PORT DESIGN
TO
TO INDOOR COIL
ACCUMULATOR
VIA SERVICE VALVE
ON OUTDOOR COIL
INSULATE
FOR
ACCURATE
TP-3
READING
TP-1
ELECTRONIC
THERMOMETER
De-Energized)
A91457
TP-2
A88341