Heat pump TXV sensing bulb location

Discussion in 'HVAC Heating & Cooling' started by Slicker, Oct 3, 2020.

  1. Slicker

    Slicker New Member

    Joined:
    May 25, 2020
    Location:
    Charlottesville, VA
    I had a question about the TXV sensing bulb location on my heat pump in the external compressor unit. From what I've read online, the TXV valve sensing bulb should be located on a horizontal run but can also be located vertically with the tail end up if there's no suitable horizontal run. On my unit, the sensing bulb is located vertically (doesn't look like there's any place where it could go horizontally) but the tail/tube leading to the valve is pointing down. I've attached a picture showing the sensing bulb location on my system.

    Is this location/install incorrect and would this impact the performance of the heat pump (e.g. lower return temperatures)?

    Thanks in advance. IMG_9064.jpg
     
    Last edited: Oct 3, 2020
  2. WorthFlorida

    WorthFlorida The wife is still training me.

    Joined:
    Oct 28, 2009
    Occupation:
    Retired
    Location:
    Orlando, Florida
    If that is where it came from the factory, its OK. What you have read is horizontal is the preferred way to mount the bulb, not the only way.
     
    Last edited: Oct 3, 2020
  3. Sponsor

    Sponsor Paid Advertisement

     
  4. Slicker

    Slicker New Member

    Joined:
    May 25, 2020
    Location:
    Charlottesville, VA
    That's the rub, I'm not sure how it came from factory. Long story but I went through three techs trying to diagnose a seemingly random compressor shut down problem (it turned out to be a leak and low refrigerant). One of the techs diagnosed a faulty TXV and may have moved the sensing bulb to the horizontal line just before it left the cabinet. The tech that found/repaired the leak appears to have moved it back to the place it is now. I have a twin unit for the upstairs that is the same brand but lower capacity. The upstairs unit has the sensing bulb in the same location but with the capillary tube in the up position. So maybe it is the factory location?

    Just curious if a TXV that isn't causing starvation or flooding problems would have any impact on efficiency if it was installed incorrectly (e.g. not insulated, poor contact with pipe, capillary tube in wrong position etc.).
     
  5. WorthFlorida

    WorthFlorida The wife is still training me.

    Joined:
    Oct 28, 2009
    Occupation:
    Retired
    Location:
    Orlando, Florida
    The tube should be not be running down. You want gas to control the valve, not a liquid. Since it looked old I assumed that it was the original but there may not be enough slack to invert it. Realize that the outside TXV is only used when you're in heat mode. The outside ambient air is cool to begin with so most of the time the valve will be at its minimum opening. You would only get a flooding problem if the TXV is opened too much, it then allows too much refrigerant into the evaporator and it leaves the evaporator as a liquid and that can cause damage to the compressor. The current position of the tube is acting like a p-trap so some liquid refrigerant remains in the bulb but the bulb may also be full of gas. It needs to be inverted or moved.
     
  6. Slicker

    Slicker New Member

    Joined:
    May 25, 2020
    Location:
    Charlottesville, VA
    Thanks. I went ahead and re-positioned the sensing bulb since there was enough slack to move it so the capillary tube was facing up.

    What's the purpose of the outside TXV valve if its mostly closed during heating operation?
     
  7. WorthFlorida

    WorthFlorida The wife is still training me.

    Joined:
    Oct 28, 2009
    Occupation:
    Retired
    Location:
    Orlando, Florida
    It's a metering device. In Heat mode the reversing valve does just that, heat is dissipated in the air handler and heat is absorbed from the outside air. The AC operation is reversed, you are cooling the outside air therefore metering device is needed as not to flood the compressor. The outside unit becomes the evaporator and the coil in the air handler becomes the condenser. On YouTube, search "ty branaman". This one explains basic heat pump operation. He has a lot of videos but youtube doesn't list all of them. You need to search "ty branaman TXV" . Just use his name and subject manner.

     
  8. fitter30

    fitter30 Active Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Copper and bulb need to be clean, insulated and tight to the tubing. Stainless hose clamp works well.
     
Similar Threads: Heat pump
Forum Title Date
HVAC Heating & Cooling New heat pump instalation Friday at 2:54 PM
HVAC Heating & Cooling Thermostat for heatpump fails three times and counting Jul 19, 2020
HVAC Heating & Cooling Heat Pump and Droop? Feb 8, 2020
HVAC Heating & Cooling Gas Heat vs. Heat Pump in Spray Foamed New Construction Jan 28, 2020
HVAC Heating & Cooling Heat Pump vs Central Air Unit Oct 2, 2019

Share This Page