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Grundfos pump replacement

67GCBC Member Posts: 3
So, I am replacing my grundfos 15-42 with a grundfos 15-58FC, controlled by a Honeywell 8124C. The -42 only required two wires, whereas the -58FC calls for the use of a green ground. There are only two wires coming from the aquastat, I’d assume a line and a neutral. Has anyone used this setup, and if you ran a grounding wire, what did you ground it to?


  • delta T
    delta T Member Posts: 883
    On the power coming into the L8124 (the wires connected to L1 and L2) is there a ground wire connected to the green grounding screw at the bottom of the control box? If so, just run your grounding wire from the pump to that. Make sure the C1 contact in the control connects to the L contact in the pump and C2 in the control to N in the pump.

    If there is not a ground in the control box you should really consider getting a properly grounded circuit to the boiler to make sure it is safe. Even though this is a low probability, without a proper ground you have the potential to energize the heating and water piping in your house :#

    (pun intended ;) )
  • 67GCBC
    67GCBC Member Posts: 3
    I have the L1&L2 wires, but no other ground wires. There is a screw with a copper base right next to where those wires come in, but it isn’t green and as far as I can tell there aren’t any green screws. I’ll attempt to provide photos.
  • 67GCBC
    67GCBC Member Posts: 3
    Here’s what it looks like.
  • SuperTech
    SuperTech Member Posts: 1,943
    I would consider replacing the wire. You can buy small lengths of MC/BX wire at most hardware stores. 10-15 feet of wire doesn't cost much and it's worth the piece of mind knowing that your equipment is grounded properly.
    EBEBRATT-Ed Member Posts: 13,824
    Having a green or bare "equipment grounding conductor" run with the circuit conductors is considered best.

    It is not however NEC code required if the conductors are in BX, greenfield (under some conditions), sealtight (under some conditions) or metal conduit.

    There are millions of older installations that do not have a ground conductor wire. The ground path is through the metal conduit, cable armor etc.

    It is important when using conduit, greenfield, bx etc. That all connectors and locknuts are made up tight and screws are secure
  • hot_rod
    hot_rod Member Posts: 19,933
    If the wiring in the aqua stat or relay is not grounded, really no value in adding a green ground between it and the pump?

    As Ed mentioned most metallic conduits would qualify as a ground and the boiler, being connected to a water line may be considered grounded. Looks like it could be romex? If so that really should not be exposed either.

    Probably buy grounded Greenfield or such at box stores by the foot.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • ch4man
    ch4man Member Posts: 294
    i believe the 42 has a metal control box and the 58 is plastic thereby making the metal conduit useless as an EGC.

    you should run new bx cable w/ground
  • Our 0015e is a 3 speed, ECM circ, does not have a ground connection (encapsulated winding).