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Before starting, insure the
blower wheel, indoor and outdoor
coils are clean.
Is sub cooling at the
outdoor unit between
8 to 12F?
Verify line set is
sized properly
for application
NO
Is sub cooling less
YES
than 8F?
NO
Confirm that
charge is
correct.
18-AD25D1-4C-EN
Is superheat
YES
YES
< 5F?
NO
Is superheat
< 20F?
NO
Is the liquid line
temperature at indoor
NO
coil within 8F of outdoor
liquid line temperature?
YES
Is indoor
temperature more
NO
than 85F?
YES
The system is running at max
capacity and this may be
causing the High superheat.
Wait until indoor temperature
is less than 80F and check
superheat again.
Confirm that charge
is correct and look
for dirty or restricted
outdoor coil.
Is air flow at least
NO
350 CFM per ton?
YES
YES
Remove sensing bulb from the
suction line. Measure superheat
at indoor coil while holding the
bulb in bare hand for one minute.
Does superheat decrease?
NO
Verify inlet screen
Has TXV screen
of inlet tube
NO
been checked and
assembly is clear
cleaned?
of debris
Replace the
Inlet screen located in liquid line. Check, clean, &
replace if necessary.
Installer's Guide
Correct air
flow
problem
TXV is OK
Measure superheat at indoor coil
YES
while placing the bulb in an ice
and water bath for one minute.
Does superheat increase?
NO
YES
TXV
YES
5
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