Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Liquid floodback

Smaller amounts of liquid will definitely attack the weaker portions of the compressor first, the valves being right up there.

I always tell my guys to ask themselves "WHY?" when they are faced with a situation. In your case, it might go something like this:

1 - The compressor is operating, but bno refrigerant is moving through the system. WHY?

2 - (after testing the unit) The compressor has defective valves. WHY?

3 - Liquid refrigerant has entered the compressor. WHY?

4 - The metering device was overfeeding the evaporator. WHY?

5 - The thermal bulb was not secured properly. WHY?

You get the picture.

Don. You are absolutely correct to mention that ALL thermal bulbs should be wrapped to ensure that the bulb will sense the suction line temperature accurately.

Some individuals are under the assumption that, as long as the thermal bulb is located with in the confines of the air distribution system, the bulb does not have to be insulated. Such could not be further from the truth.

The evaporator is able to absorb heat becasue it is at a temperature that is lower than the air passing through the coil. The suction line is also at a temperature that is lower than the air passing over the coil. By not insulating the bulb, it will be exposed to a higher temperature and, therfore, the pressure in the bulb will rise. This will cause the TXV to open wide.

Thanks for the great post, Don.


  • don_163
    don_163 Member Posts: 67
    liquid flood back.

    Does it take out the valves first?

    A system we put in last summer the compressor would not pump.Found a loose thermal bulb with only one screw and no
    thermal wrap on the bulb.

    Thats another question why are alot of company not wrapping
    the bulb now days?Could be they're walking over a dollar to pick up a dime?

    Anyway did nothing to the bulb and charge it up in ac mode
    in dail it in.Subcool and superheat in the safe zone.

    Then I flip it over to heat to see the superheat plunge to zero.Shutdown unit and tighten down the bulb and wrap it.
    The superheat came up and maintain around 15 degree.

    Darn it...that two compressor replace thus far this year under warranty.

  • Jeff Lawrence_25
    Jeff Lawrence_25 Member Posts: 746
    What's that saying?

    Compressors don't die, we kill them.
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380

    The saying is:

    "Old fisherman never die, they just smell that way"
  • Ron Schroeder
    Ron Schroeder Member Posts: 998
    \"Old fisherman never die,

    they just smell that way" Hey keep me out of this I didn't do anyting to you ;-)
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Nothing personal

    Nothing personal, Bruce.
  • RadPro
    RadPro Member Posts: 90
    Speaking of TXV bulb placement!!

    Quite a few years back I serviced a Lennox split system. Can't really remember if yearly maintenance or problem, but here I am and I take a look at the A-coil.

    A second look and again, what is wrong with this picture? That's it the txv's sensing bulb is attatched to the liquid line! I could not believe it. I asked the customer if they ever had trouble with the ac not working right, not that they could remember.

    So I move it where it is supposed to be and continue with the check. Everything was fine, I could not believe it!

    You just never know what you will run into!!

    Don in SEIA
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    I have never....

    I've never heard of that one before...

    Although I have heard about the suction line being connected to the condensate drain fitting.

    No cooling? Gee... I wonder why... No wonder why they couldn't pull a decent vacuum!
  • Blackoakbob
    Blackoakbob Member Posts: 252
    I just had one...

    that was always flooding back to the compressor and making a rattling noise that the owner asked me to check 'cause it annoyed him. Well, all it was that the duct tape holding the txv bulb to the suction line was loose, imagine that. LOL Best regards.
This discussion has been closed.