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To determine that a TXV has failed, verify the following:
•
The suction pressure is low and the valve is non-
responsive.
•
The TXV sensing bulb can be removed from the suction
line and warmed by holding the bulb in your hand. This ac-
tion should result in an increase in the suction pressure
while the compressor is operating. The sensing bulb can
also be chilled by immersion in ice water, which should re-
sult in a decrease in the suction pressure while the com-
pressor is operating. No change in the suction pressure
would indicate a nonresponsive valve.
•
Simultaneous LOW suction pressure, HIGH refrigerant
subcooling and HIGH superheat.
•
LOW suction pressure, LOW subcooling and HIGH super-
heat may indicate an undercharge of refrigerant. HIGH
subcooling and LOW superheat may indicate an over-
charge of refrigerant. The suction pressure will usually be
normal or high if there is an overcharge of refrigerant.
•
LOW suction pressure and frosting of the valve and/or
equalizer line may indicate a failed valve. However, these
symptoms may also indicate an undercharge of refrigerant.
Calculate the subcooling and superheat to verify a failed
valve or refrigerant charge issue.
Repair
WARNING
Puron
refrigerant (R-410A) operates at higher pressure than
®
R-22, which is found in other WSHPs. Tools such as manifold
gauges must be rated to withstand the higher pressures. Failure
to use approved tools may result in a failure of tools, which
can lead to severe damage to the unit, injury or death.
WARNING
Most TXVs are designed for a fixed superheat setting and are
therefore considered non-adjustable. Removal of the bottom
cap will not provide access for adjustment and can lead to
damage to the valve or equipment, unintended venting of re-
frigerant, personal injury, or possibly death.
CAUTION
Always recover the refrigerant from the system with suitable
approved tools, recovery equipment, and practices prior to at-
tempting to remove or repair any TXV.
Use caution when tightening the strap. The strap must be tight
enough to hold the bulb securely but caution must be taken not
to over-tighten the strap, which could dent, bend, collapse or
otherwise damage the bulb.
Puron
refrigerant (R-410A) requires the use of synthetic lu-
®
bricant (POE oil). Do not use common tools on systems that
contain R-22 refrigerants or mineral oil. Contamination and
failure of this equipment may result.
IMPORTANT: Due to the hygroscopic nature of the POE oil in
Puron refrigerant (R-410A) and other environmentally balanced
refrigerants, any component replacement must be conducted in a
timely manner using caution and proper service procedure for
these types of refrigerants. A complete installation instruction
will be included with each replacement TXV/filter drier assem-
bly. It is of critical importance these instructions are thoroughly
understood and carefully followed. Failure to follow these in-
structions can result in a system that is contaminated with mois-
ture to the extent that several filter drier replacements may be re-
quired to properly dry the system.
IMPORTANT: Repair of any sealed refrigerant system requires
training in the use of refrigeration tools and procedures. Repair
should only be attempted by a qualified service technician. A
universal refrigerant handling certificate will be required. Local
and/or state license or certificate may also be required.
Figure 47 illustrates the typical refrigerant diagram for 50PC units.
See Table 33 for additional troubleshooting information.
Disconnect power from unit before removing or replacing
connectors, or servicing motor. Wait 5 minutes after discon-
necting power before opening motor.
61
CAUTION
CAUTION
CAUTION
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