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Honeywell L8148J Aquastat bulb seized.

Twilt Member Posts: 1
Can anyone tell me how to remove the bulb from the well. Mine is seized. The conductive compound appears to have hardened. I have tried to dig it out and not making much headway. Right now I am soaking it in WD40.

These aquastats are really garbage. My boiler is 20 years old and this is the fourth one I have had to install. (maybe more) The first two I had serviceman install, but it came to the point that I knew the symptoms so I did it myself. Saved a service call and the markup on the part.


  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 3,717
    edited November 2018
    If the bulb has seized, what else can you do? Replace the well, no?

    Aquastats aren't garbage, you just have to deal with them. As the French say, "Get over eet.".
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    HVACNUT Member Posts: 5,247
    ^^^ Yes, replace the well, in which case you need to cut the capillary. So it's a good time to upgrade the aquastat to one that offers LWCO, ODR, etc.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,237
    You could try some heat, maybe it will melt the paste, but you should replace the well.
    In my almost 30 years I've probably replaced 2 dozen aquastats, and never the same one twice.
    I think something else is going on-bad install, bad ground, bad voltage (spikes or shorts) or the well is limed up inside the boiler and not sensing temperature correctly.
    You didn't say why it failed.
  • rick in Alaska
    rick in Alaska Member Posts: 1,429
    That is also the reason that the heat conductive past is not recommended to be used. The stuff hardens and the probe is stuck. I don't think it makes very much difference at all by using it, so you are better off not.
    And yes, you are either going to have to drill it out, which won't get it all out, or replace the well.
  • GBart
    GBart Member Posts: 746
    Agreed, after killing myself trying to get a probe out of a well with the paste it in I never used it, ever.
  • Tim McElwain
    Tim McElwain Member Posts: 4,593
    There is new stuff in a tube that does not harden. Sorry I do not have the brand name but I believe it comes from Honeywell or White Rodgers.
    rick in Alaska