Sysem Pumping Down

[NANOTECH]

I have a Trane Heat Pump Md# 2TWB3036A1000AA that keeps pumping down and shutting off on LP control!!! Nameplate says it takes 7lbs. 6 ozs. R22. I start out with around 170 head and 80 suction then she starts pumping down and shuts off on LP control at 5psi then cuts back on around 20psi. I recovered out all the refrigerant (8lbs.) and installed a new filter dryer pulled a vacuum and put the refrigerant back in. It did the exact same thing. FLA is 14amps I'm pulling 6.5amps. Could this be a bad TXV? If the compressor had bad valves would I have these symptoms? Any therories to what the problem is here?!!

[Tech83]

Did you purge with nitrogen thru the line set from one side to the other? I would look at kinked or blockage in liquid line. (Have also heard guys forgetting to pull plugs on new driers, the new one's have caps and thin/small black plugs that get misses. ) Temp readings on line might help you isolate the issue.

[choptank]

I would lean towards a bad txv or restriction. Just had a system that did the same thing. would pump its self down and cut out on low pressure. took like 10 mins to equalize. bulb line rubbed though.

[Rubio480]

TXV


We all make choices, but in the end our choices make us.

[ICanHas]

What does it do in heating mode? Use two high side gauges on outside ports and low side port on compression suction port inside the unit.

In cooling mode, compare the suction line at compressor and vapor line port which should be roughly the same.

If there's something inside the liquid line between the inside and outside, it will go back and forth and don't expel.

[gravity]

Are the service valves open?

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[ajharris904]

I would say it's the txv switch it to heat and see what your pressures do, if there is a restriction it will show,but it also show if your heating valve is good or bad

[gravity]

Trane has a check valve inside at the txv. It will bypass the indoor txv in heating.

You also need to look at the filter drier and see if it filters in both modes. Some tranes used 2 driers. Other tranes had 2 driers and a charge compensator that looked like a drier.

Keep us posted

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[Mike703]

txv i did nothing but trane warranty work for years, classic. also almost anytime you see an aspen coil on a trane system and its low on refrigerant you can just about guarantee with 90% accuracy that its the coil.