Help rewiring a replacement Aquastat

Discussion in 'Boiler Forum' started by jordan69s, Oct 22, 2011.

  1. jordan69s

    jordan69s New Member

    Apr 14, 2009
    Thanks for reading my post.

    Well, it is a Weil-Mclain boiler, the numbers I found were: 1269463
    boiler size: P-466HE
    144BTU HR
    30PSI water
    1.25 nozzle
    series 3
    water 125.2mbh

    Wiring of the original Aquastat

    T- white wire to R845A
    Tv- red wire to R845A
    Z empty
    Zc yellow wire to ignition (R8184G)
    B2 White to ignition
    Zr empty

    The new Aquastat has:

    T W Tv (It says thermostat)
    B1 & B2 (burner)

    line --- S2.... C1 C2
    S1.... L1 L2

    This boiler used to have an internal coil to make how water for the showers, and someone cut the pipes, left the original Aquastat L8124L, and setup an indirect fired water heater. My friend told the that the original Aquastat has a low and high setting, so that during the summer, the boiler was still "maintaining" the heat for the baseboards, though using more oil. He suggested replacing it with this L8148A which would only have one high setting (setup to 180 degrees). Lastly he said that the wiring between the two units were the same so I could just follow up the wiring. The house has 3 floors, and the baseboard lines have 4 loops, one per floor and one for the bedrooms, but it did not have any zone valves; so when the only thermostat on the lower floor will call for heat, the whole house would "light up", so now I incorporated the zone valves. All I have to do now is to figured out the wiring... I have done wiring for zone valves in the past which was pretty straight forward, but someone told me that because I changed the Aquastat, that the wiring should be redone! Of course he could not told me how.

    So as of right now I replaced the aquastat with a L8148A (not wiring done yet) and added the zone valves (no wiring done). I have an electrical background, so it would be easy for me to follow an electrical diagram. Would a kind soul be able to draw me a diagram I could follow up to wire up this boiler?

    I would greatly appreciate the help since the boiler is down until I get the wires done :(

    DSCN9193.jpg DSCN9199.jpg
  2. Tom Sawyer

    Tom Sawyer In the Trades

    Nov 29, 2010
    Replacing the aquastat has no effect on the zone valves at all. The L8148 has two terminals ( T T ) that call the burner and circulator. I'm not sure what you have for zone valves but in any case there will be two wires or terminals from the zone valves that switch TT. These should be wired in parallel to TT on the 8148

    You can find wiring diagrams for pretty much anything old or new at

    You could have saved yourself some money by leaving the 8124 and just pulling and capping the blue wire which disables the low limit function. Oh well, live and learn
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  4. BadgerBoilerMN

    BadgerBoilerMN Hydronic Heating Designer

    Mar 4, 2011
    hydronic heating designer/contractor
    You may consider a new boiler...but no rush.
  5. Tom Sawyer

    Tom Sawyer In the Trades

    Nov 29, 2010
    I would be for sure
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