txv expansion valve insulation

eric_kJune 13, 2008

When insulating an expansion valve bulb after securing to the suction line, anyone know if there's a critical way to insulate it? Just wrap them both together, or try to cover as much copper as possible on each without wrapping in between the two? Maybe it doesn't matter as long as you've insulated? I've tried to cover as much as the copper as I can without separating the two with insulation where they meet, but was wondering if I could be interfering with the temperature sensing. Maybe I am over-thinking this.

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If the line and bulb were cleaned and clamped to the line properly there is no way that you could put insulation between them. The temperature transfer is at the point of direct contact between the line and the sensing bulb. Wrap the insulation around the outside to your hearts content as long as it is properly cleaned and clamped it will work well.

    Bookmark   June 13, 2008 at 1:40PM
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Do you have the sensing bulb clamped at the right angle ?
You don't just clamp it in place and hope it works. Are you
using the proper clamps ? Don't even think of using hose
clamps. What have you done so far ?

    Bookmark   June 13, 2008 at 5:42PM
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Actually a professional put it on, it's clamped horizontally at 2 o'clock position. I believe he used clamps that came with it. Another question... I remember him saying the new expansion valve had a longer bulb than the old one, does that necessarily mean he put an incorrect valve on or could the bulb size vary by manufacturer? The new one has a label on it saying to use the same part which made me wonder about the difference in bulb size. It seems to be working. He did take the old one with him because originally he said he got the wrong one... took it with him so I'm hoping it is the right one and bulb size doesn't necessarily mean it's incorrect part???

    Bookmark   June 13, 2008 at 10:18PM
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Sounds like it is in the right position and yeah you are probably over thinking it if you just wrap it with foam tape or over wrap it with a larger piece of pipe insulation you should be fine you are just trying to keep the temperature of the ambient air from interfering with the pipe temperature the bulb is sensing

Here is a link that might be useful: Air Conditioning Repair made Easy

    Bookmark   June 14, 2008 at 4:06AM
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The bulb should be at 10 or 2 o'clock per the install manual that I have.

There should be a "beer can" black foam blanket for the TXV itself. Mine came with that plus some black foam tape.

The TXV for the indoor coil is different for heat pump, straight a/c, 410, or R-22.

Good luck.

    Bookmark   June 14, 2008 at 2:08PM
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"There should be a "beer can" black foam blanket for the TXV itself."
AHH HA! I think gary just figured out why most HVAC techs consume vast quantities of beer! Especially those who do alot of work with TXV's :-)

    Bookmark   June 14, 2008 at 4:31PM
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