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CONTROL VALVES
6 - 8
Table 6-4 — Troubleshooting the TEV
Malfunction
Cause
Evaporator
Superheat adjusted
Starved
too high
Moisture
Dirt plugging strainer
or valve mechanism
Wax
Equalizer
Internal misapplied
External plugged
Capped
Restricted
Incorrect location
Flash gas upstream
of TEV
Insufficient pressure
drop across valve
"Dead" Bulb
Undersized TEV
Superheat adjusted
Evaporator
Flooded
too low
Bulb not getting
good thermal pickup
Moisture or dirt
holding valve open
Oversized TEV
Valve damage or
valve seat leak
Poor
Uneven circuit load on
Performance
multiple evaporators
Moisture or Dirt
TEV mis-sized
HUSSM ANN CORPORATION • BRIDGETON, M O 63044-2483 • Printed in USA
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Action
Adjust to proper superheat
Dehydrate and install new liquid line filter dryer
Remove and clean or replace
Clean valve and install wax trapping dryer
Install externally equalized TEV
Clear
Install properly
Correct or re-pipe
Re-pipe
Head pressure too low, raise head pressure
Liquid supply line not exiting branch line from
bottom, re-pipe
Liquid supply line too small, re-pipe
Raise head pressure
Install valve with adequate capacity at reduced
pressure
Replace
Install correct size
Adjust to proper superheat
Check bulb and correct for good contact, location,
and ambient influence
Clean and dehydrate and install new liquid line
filter dryer
Install correct size
Repair or replace
Balance load (lightly loaded evaporator is
controlling TEV, starving loaded evaporator.)
Clean and dehydrate and install new liquid line
filter dryer
Install correct size
September 1, 1997
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