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Pressusretrol replacement

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mel rowe
mel rowe Member Posts: 324
in Thermostats and Controls
Thanks Mark for your reply. You were right that I do have a PA404A Pressuretrol. You recommended as a replacement the L408A. Could you explain how this is different than the L608A-1046 vaporstat, and why would it be better for me? Thanks very much. Mel

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  • mel rowe
    mel rowe Member Posts: 324
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    When the boiler on my old one pipe system was replaced, the installer put in a gauge that read from 0-50 psi. Obviously that was useless to me. I finally replaced it this week with a 0-5 psi gage and now I have found that my old pressuretrol Honeywell 404B has been breaking at 2 1/2 and making at 1 1/2, about 1 psi above where it should. I'mk thinking of replacing it with a vaporstat, after reading Dan's book. There are several listed in the Honeywell L608A family. My question is which one is the correct one to use as a replacement? Thanks.
  • carol_3
    carol_3 Member Posts: 397
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    I'll see what I can find out. Anyone else know?
  • superMARKet
    superMARKet Member Posts: 87
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    Vaporstat

    Are you sure you've got a "B" control (L404B or PA404B)? Those make a circuit when the pressure rises and aren't typically specified as controls on low-pressure steam boilers, where you want the burner to stop when the pressure rises. It sounds to me like you've probably got a PA404A instead. Could you take a closer look at your control and verify?

    Assuming you've got a PA404A on there now, you'll want an L408A Vaporstat, specifically, L408A1157. This will give you 0-4psi cut-out and 2-16oz/sq.in. subtractive differential.
  • mel rowe
    mel rowe Member Posts: 324
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    Pardon me Mark, I do have a PA404A. So you said that I would need a L408A1157. Could you please enlighten me as to why this version, rather than the L608A1046? I'm just trying to increase my understanding of these things. I looked at Honeywell's site and could find no info at all. Thanks for your help.
  • superMARKet
    superMARKet Member Posts: 87
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    L608A has extra contacts

    The L608A makes one circuit and breaks another on pressure rise (it's an spdt switch). Using the 404A/404B pressuretrol example from above, the 608A combines the features of both. You don't need the extra terminal, but other than the possibility of wiring confusion and about $15, it's the same thing.

    Note that I specified L408A1157, which is 0-4psi. L608A1046, what you asked about, is 0-1psi. The 608 equivalent with the wider range is L608A1053. You get 16oz/sq.in. adjustable subtractive differential with any of these. Having a 4psi top end gives you a little bit more flexibility, in my opinion.
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