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L7224U/R832A Compatibility

I have replaced my old aquastat with a Honeywell L7224U. The existing relay for the second zone is a Honeywell R832A. Currently the thermostat for zone two runs the circulator but will not start the burner. Is the 832 compatible with the L7224U or do I need to replace that relay as well? I currently have it fed from ZC and L1. It seems to me that I should be able to make it work but I don't want to blow out a new aquastat trying.



  • Robert O'Brien
    Robert O'Brien Member Posts: 3,385
    Needs an 845 or similar. ZC is hot when the boiler temp is above the LL
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  • WalleyeHunter
    WalleyeHunter Member Posts: 3
    Thank you, that explains how it worked with the old aquastat. And I've been reading a bit about a taco relay, are they a better choice?
  • icesailor
    icesailor Member Posts: 7,265
    edited November 2014
    You can wire the R832 also. Its just more complicated. You can use the Taco 501 and it will cover every application that the Honeywell 832 and 845's do and more. It is a universal replacement.

    Its the ZC and ZR connections that are giving you the problem.

    The 832 has the two "X-X" contacts which are dry low voltage contacts that are for operating low voltage equipment. With the 845, terminals 5 & 6 are dry contacts that have no power to them.

    Once you understand how ZC & ZR works, you will need to explain it to Sparky. They really have a hard time with it if they only run house wiring. Watch what happens when they have to wire a 4-way or 5 way switch. Wiring ZC & ZR is kind of like that. Easy once you get the concept.

    Here's the Honeywell Cut Sheet for the R832 and all the other Honeywell relays of that class. The Taco SR501 covers every one of those relays. My aged memory is getting frail. The SR501 will solve your problems if you want to change controls.
  • WalleyeHunter
    WalleyeHunter Member Posts: 3
    Since I already have the R832A in place and it's only back up for the wood stove I would keep it if I could figure out how to wire it. If someone could just tell me hook x to zr, etc I could make it work. I'm thinking I could almost do it on my own but having just replaced that aquastat and it's all computerized I could see myself smoking a circuit board.