Replaced TXV and still not working!

charliechicago

Hello to all,
I recently went on an ac call that I am having trouble with. The condenser was very dirty so I chemically cleaned it and then checked pressures. Its a ten year old Trane 410A 13 SEER horizontal cased coil/furnace TXV unit in the attic. Started it up and these were my approximate pressures/temperatures.
275 PSI/85 degrees high side and 100 PSI/30 degrees low side. 14 degree Subcool and 35 degree superheat. 70 degrees outside and 74 inside. I added two pounds 410A and my head and suction pressures remained the same and my subcool started to climb. I thought is was the TVX or a restriction. I took out the old TXV and blew out the lines from the condenser up to the air handler. No apparent restriction (nitro flowed strong and no debris came out) and strainer seemed clean. Came back later in the week with the TXV. Installed it and replaced filter drier. Getting the same pressures/temperatures again, except now my suction is down to 62 PSI/10 degrees.
Any ideas?
Regards, Michael.

pecmsg

Is the evaporator fan even turning?

HVACNUT

What was the temperature drop across the evaporator?
How's the air filter?
Is it moving air? Static pressure?
The 100/275 pressures don't seen too out of range but don't know what Trane wants. What do they spec for sub cooling on that model?
I'm sure you trickled nitro while brazing and did a triple vac after the TXV and drier. 
Do you have history with this equipment?
Did you put back the same refrigerant you recovered? Was it converted from R22 using existing the line set? Could be oil, noncondensables, or mixed refrigerants.
The 40 psi drop on the low side is weird.

charliechicago

Thanks for response.
Fan is running. Filter is clean. 13 Degree temp drop across coil. Don't know static pressure. I agree high side and subcool looks normal. I pumped unit down, brazed filter drier while purging nitro but did not triple evacuate. Unfortunately I don't have any history with this unit. This was a completely new 410A install 10 years ago (not a replacement of R22)

HVACNUT

Are pressures stabilized or fluctuating?
Try taking the TXV bulb off the suction line and see if there's any changes. 
You did not triple vac, but did you vac at all?

charliechicago

pressures are stable. I will take off bulb when I go back tomorrow and of course I pulled vacuum. 

Thanks. 

pecmsg

Airflow
airflow
airflow

You’ve got 1 or 2* SH!

charliechicago

No. Superheat is 35 as posted. 

pecmsg

100#’s and 33* is 1.5* SH. 

charliechicago

sorry for confusion 
I meant that suction pressure was approximately 100 psi which is equivalent to about 30 degrees saturation. And by superheat was 35. Meaning my suction line temperature was about 65. 

pecmsg

Did you measure the suction line temperature?

charliechicago

yes