Answer

Here is a list of what you can check for

Flash gas in the liquid line.
Insufficient refrigerant charge.
Excessive pressure drop in the liquid line due to an undersized liquid line or excessive vertical lift.
Liquid line restrictions.
Improper piping design.
Inadequate subcooling.
Low head pressure.
Expansion valve distributor or cap tube restricted.
Excessive load on the evaporator above the design conditions.
System contamination, probably moisture or rarely, wax.
Undersize expansion valve.
Internally equalized expansion valve used on a system with too much pressure drop thru the evaporator or used with a refrigerant distributor.
Expansion valve power element has failed or lost its charge.
Incorrect expansion valve power head charge.
Oversized evaporator or undersized compressor.
Superheat setting on expansion valve too high.

Expert:	Rick Mather
Pos. Feedback:	96.1 %
Accepts:
Answered:	6/8/2009

HVAC Technician

35 years experience, HVAC