bad txv or bad suction valve

[timjimbob]

How can you determine which it is?

Scrolls don't normally pump down.

I seem to remember, a bad suction valve will have low SH.

[pecmsg]

Scrolls can pump down and don't have valves.
Look up the performance curve for the vompressor

[timjimbob]

usually they bail at 30 or 40 psi

[jtrammel]

usually they bail at 30 or 40 psi

No usually they pump down unless it has a LPS which you can jump out. Scrolls don't have valves.

Generally txvs fail in the closed position with low suction pressure and high superheat. I have seen them fail open though. What's your subcooling?

Low superheat is usually due to low airflow or overcharge.

[timjimbob]

SH 40 SC9

[jtrammel]

SH 40 SC9

More than likely bad txv

[kdean1]

No usually they pump down unless it has a LPS which you can jump out. Scrolls don't have valves.

I've had many which opened the IPR when suction pressure was still over 100 PSI. That stinks because I have to recover the refrigerant for a repair on the indoor coil.

[TechmanTerry]

What is the evap SH? The SH should be the same, KindaSorta, a 10* SH should still be 10* w / leaking suction reeds or even a leaking scroll. Little leakers,

[CircusEnvy]

I've had many which opened the IPR when suction pressure was still over 100 PSI. That stinks because I have to recover the refrigerant for a repair on the indoor coil.

Air conditioner or heat pump?

Most air conditioners don't have enough volume in the condenser coil to pump down and hold the factory charge. IPR will generally open in this case. York started putting labels on their ODUs warning technicians not to attempt a pump down.

[tunaguy]

SSH way too high and SC may be normal which means TXV or drier or restriction. Some OEMs want 10-20 SC depending upon unit. Bad suction valves will have roughly normal but never low SSH. To me the scroll vs a recip does not apply hear.

[DaltonsLaw]

I've pumed down all scrolls... that hold. Internal check valve.