[floser]

My Trane is showing roughly a consistent 100 PSI on both liquid and vapor side at the service connectors with and without the compressor running. It kicks in and run for around 5 minutes then shuts down and will not start again. This must be due to thermal protection, but not sure why the pressure is consistent.

 

[Plumber101]

Are you sure the manifold gauge valves are closed?

If they are are you sure the compressor is coming on?

What is the amp draw?

If you are 100% sure the compresor is coming on then your compressor valves are shot and you need a new compressor/condenser.

You may also have a compressor capacitor not allowing the compressor to start fully.

 

[floser]

yes, the gauge is closed. The compressor is running like it is supposed to. I did not check the amperage, but it did not trip the breakers when fan/compressor running so I assumed that it is within range. I' ll check tomorrow.

This unit was running fine when installed in another house. A new heatpump was installed in the other house and hoping to reuse this one in mine. I swap my 15 yr old old unit for this unit (8 years) - replaced both condenser and evaporator to make sure it is compatible. The lines are identical in sizes.

Is there an easy way to test the compression.

 

[Plumber101]

How did you charge this? Weigh it in?

Did you pull a vac on the system?

Did the system have a filter and if so did you replace it?

Sounds like something come loose and either caused the TXV (EVAP) to stick open or something got into the valves of the compressor.

 

[floser]

Full vac and weighed it, 8 lbs into system (8.5 is max on sticker). It's an XL 1200 (TTX042D100A0). I capped it after removing from original location until I got it back home. I don't think there is a filter in this unit. My original system was working but not very efficient, so I though this would be a good free upgrade.

Do you think it would help/good idea to disconnect the lines and flush with air in reverse?

I'm pretty sure the TXV is working, but will remove the bulb tomorrow and see if the TXV is working.

 

[Plumber101]

What happens when you make a call for heat?

What are your pressures?

 

[floser]

Works fine when calling for heat, furnace kicks in fine. This is not a heat pump, just AC unit.

 

[SKIP4661]

If it is a scroll compressor it could be running backwards.

 

[Plumber101]

Sorry, picked up on HP early in post.

Check amps, check cap and may need a hard start.

 

[biggles]

100 PSI with the unit off and 80F outside your short of gas....if the unit starts and the pressures don't change and it is a hermitic compressor the valves are shot or the drive is scrambled for the piston

 

[kennzz05]

broken crank? can you rapidly pull the disconnect out and push it back in and have the compressor start everytime? unhook the fan motor so you can hear what the compressor is doing also as mentioned amp draw will give you an idea what is happening with the compressor

 

[floser]

its a Scroll and the compressor starts everytime when the disconnects are manually engaged. The compressor hums like usual. Draws about 8 amps.

 

[Plumber101]

Install a set of gauges.

Close high service port valve

Manually engage the contactor

Watch gauges to see if the pressure will go to zero and continue running until it goes into a vac.

If the compressor won't do that then the compressor is junk.

If it will then the txv

 

[HvacWiz]

If it is a scroll compressor it could be running backwards.

Only on 3 phase units, not many homes have 3 phase a/c, at least i've never seen it.

 

[yuri]

A scroll can go backwards if it is started and stopped very quickly. Was reading about that in Lennox tech info. They ALSO state that you should not pump down a scroll compressor to less than 7 psig as the fusilite plug can start arcing internally and the compressor may get damaged. Has to do with the way scrolls are lubricated. DO NOT run them into a vacuum!!

 

[Plumber101]

Thanks for the update Yuri. Did not know that.

But still trying to pump down the system will tell this guy if the compressor is Crap

 

[yuri]

Sounds like it is shot anyway. Didn't know about the 7 psig but read a lot of Lennox tech stuff to keep ahead of the other guys in my area. Doesn't help that most units have no low pressure control anymore due to the dumbing down and cost cutting of the industry driven by builders grade units and customers not willing to pay for quality.

 

[floser]

Thanks yuri, luckily did not have a chance to pump it into a vacumn. Thanks plumber, will do want you suggested but only to 7 psi, hopefully it works. Thanks again for all you guys help.

 

[hvaclover]

A messed up run cap can cause it to run backwards too.