Heat Controller HRE1318/1360-1A Installation And Operation Manual page 30

THERMOSTATIC EXPANSION VALVES
SYMPTOMS
Superheat is low to normal
with low suction pressure
Superheat and suction
pressure fluctuate (valve is hunting)
Valve does not regulate at all
POSSIBLE CAUSE
Unequal evaporator circuit loading
Low load or airflow entering
evaporator coil
Expansion valve is oversized
Sensing bulb is affected by liquid
refrigerant or refrigerant oil flowing
through suction line
Unequal refrigerant flow through
evaporator circuits
Improper superheat adjustment
(only possible with TEV having
superheat adjustment)
Moisture freezing and partially
blocking TEV
External equalizer line not connected
or line plugged
Sensing bulb lost its operating charge
Valve body damaged during soldering
or by improper installation
CHECK OR REMEDIES
Ensure air flow is equally distributed
through evaporator
Ensure proper piston is inserted into
RCBA or RCHA evaporator coil
distributor
Check for blocked distributor
tubes
Ensure blower is moving proper air
CFM
Remove/Correct any air flow
restriction
Install correct TEV
Relocate sensing bulb in another
position around the circumference of
the suction line
Ensure proper distributor piston is
inserted in RCBA or RCHA coil
Ensure sensing bulb is located
properly
Check for blocked distributor
tubes
Replace TEV or adjust superheat
Recover refrigerant, change filter-
drier, evacuate system and
recharge
Connect equalizer line in proper
location, or remove any blockage
Replace TEV
Replace TEV
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