Service Manual

26
6. Scratch matching marks on tubing studs and old
accumulator. Scratch matching marks on new
accumulator. Unbraze stubs from old accumulator
and braze into new accumulator.
7. Thoroughly rinse any flux residue from joints and
paint with corrosion- resistant coating such as
zinc- rich paint.
8. Install factory authorized accumulator into system
with copper slip couplings.
9. Evacuate and charge system.
Pour and measure oil quantity (if any) from old accumulator.
If more than 20 percent of oil charge is trapped in
accumulator, add new POE oil to compressor to make up for
this loss.
430° FUSE
ELEMENT
A88410
Fig. 22 – Accumulator
Thermostatic Expansion Valve (TXV)
All (post- 2006) furnace coils, most fan coils, and a few heat
pumps have a factory installed thermostatic expansion
valve (TXV). The TXV will be a bi- flow, hard- shutoff with an
external equalizer and a balance port pin. A hard shut- off
TXV does not have a bleed port. Therefore, minimal
equalization takes place after shutdown. TXVs are
specifically designed to operate with R- 410A or R- 22
refrigerant, use only factory authorized TXV’s. Do not
interchange R- 410A and R- 22 TXVs.
TXV
Operation
The TXV is a metering device that is used in air conditioning
and heat pump systems to adjust to changing load
conditions by maintaining a preset superheat temperature at
the outlet of the evaporator coil. The volume of refrigerant
metered through the valve seat is dependent upon the
following:
1. Superheat temperature is sensed by cap tube
sensing bulb on suction tube at outlet of evaporator
coil. This temperature is converted into pressure by
refrigerant in the bulb pushing downward on the
diaphragm which opens the valve via the pushrod(s).
2. The suction pressure at the outlet of the evaporator
coil is transferred via the external equalizer tube to
the underside of the diaphragm. This is needed to
account for the indoor coil pressure drop. Residential
coils typically have a high pressure drop, which
requires this valve feature.
3. The pin is spring loaded, which exerts pressure on
the underside of the diaphragm. Therefore, the bulb
pressure works against the spring pressure and
evaporator suction pressure to open the valve.
If the load increases, the temperature increases at the
bulb, which increases the pressure on the top side of
the diaphragm. This opens the valve and increases
the flow of refrigerant. The increased refrigerant flow
causes the leaving evaporator temperature to
decrease. This lowers the pressure on the diaphragm
and closes the pin. The refrigerant flow is effectively
stabilized to the load demand with negligible change
in superheat.
Install
TXV
The thermostatic expansion valve is specifically designed to
operate with a refrigerant type. Do not use an R- 22 TXV on
a R- 410A system, and do not use a R- 410A valve on an
R- 22 system. Refer to specification sheets for the
appropriate TXV kit number.
CAUTION
!
UNIT OPERATION HAZARD
Failure to follow this caution may result in
equipment damage or improper operation.
Al indoor coil units must be installed with a hard
shut off R- 410A TXV metering device.
IMPORTANT: The TXV should be mounted as close to
the indoor coil as possible and in a vertical, upright
position. Avoid mounting the inlet tube vertically down.
The valve is more susceptible to malfunction due to
debris if inlet tube is facing down. A factory - approved
filter drier must be installed in the liquid line at the
indoor unit.
Installing TXV in Place of Piston in a Rated Indoor
Coil
(pre- 2006)
1. Pump system down to 2 psig, if possible, and recover
refrigerant.
2. Remove hex nut from piston body. Use backup
wrench on fan coils.
3. Remove and discard factory- installed piston. Be sure
Teflon seal is in place.
4. Reinstall hex nut. Finger tighten nut plus 1/2 turn.
NOTE: If the piston is not removed from the body, TXV will
not function properly.
CAUTION
!
EQUIPMENT DAMAGE HAZARD
Failure to follow this caution may result in
equipment damage or improper operation.
Use a brazing shield and wrap TXV with wet
cloth or use heat sink material
5. Install TXV on indoor coil liquid line. Sweat swivel
adapter to inlet of indoor coil and attach to TXV outlet.
Use backup wrench to avoid damage to tubing or
valve. Sweat inlet of TXV, marked “IN” to liquid line.
Avoid excessive heat which could damage valve.
6. Install vapor elbow with equalizer adapter to suction
tube of line set and suction connection to indoor coil.
Adapter has a 1/4- in. male connector for attaching
equalizer tube.