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L8148 issue

Hello wetheads,

Our customer has a Hydrotherm HC85D-PV from 1996. All fine until this fall when the damper had to be replaced. Got an identical model, Field Controls, from Hydrotherm. All fine until end of December when the relay on the 8148 got intermittent. Had a used working one in the shop was going to use to get them by til we could get a new one. No luck. So figured maybe it wasn't as good as we thought.

Got a new one the next day, ran fine. We wondered about the damper so left unplgged til it got warmer. When it did we went back and plugged it in, no work. Unplugged or plugged.

SO, we dryheads don't know if there is an incompatibility between the Field Controls damper and the generic L8148 we get at the supply house or if something has since shorted out in the damper though it was working fine when we changed the original L8148.

Do we need to go back to Hydrotherm for a specially designed aquastat? Thanks for all comments.


  • Tim McElwain
    Tim McElwain Member Posts: 4,554
    When any damper

    Effikal (Now Fields), Honeywell or Johnson completes the first call for heat it blows a fuse inside the primary control it could be the relay, a module or any control the damper is plugged into. This is so you can't operate the system without the damper plugged in. If you unplug the damper the primary control will not work unless you jump out the harness.

    What model of L8148 is this is it the L8148E? If so that has a damper plug so it would be the typical control that would happen on.
  • John Mills_5
    John Mills_5 Member Posts: 935
    Thanks for replying Tim

    The aquastat we tried that worked until we plugged in the damper is L8148E1299.

    The new damper worked with the aquastat that came with the boiler. It just doesn't want to work with the generic replacements. Unfortunately we didn't save the dead OEM stat.

    Just not making sense why the damper worked on the old one but not the new ones unless the generics aren't compatible with it.
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