Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Hydronic Coil Air Haindler

Johan Member Posts: 2
I can't find a model number and think the water circulation pump may not be enough power for the system. The main water goes into the water heater. Hot water comes out of the water heater into the circulation pump to the radiator and joins back where the main water comes in to go back into the water heater. I've tested the pump, electrical, clogs, etc. All is functioning and working. There is a spout after the radiator that if I open up to bypass going back into the water heater, the hot water flows and the heater works. If I close the spout and to allow the flow to go back into the water heater to recirculate the flow stops. My guess is that the pressure from the main is more than the pressure coming from the radiator? Any help would be greatly appreciated! :)


  • icesailor
    icesailor Member Posts: 7,265
    Domestic Water Heaters & Coils:

    First, the circulator is probably broken. I've found quite a few broken impellers in circulators when piped into the bad idea you have for a cheap way to heat your house, and an expensive medical condition if the moon and stars align in the right house.

    That "Armstrong" circulator looks like a re-branded Grundfoss pump. It must be a bronze or Stainless Steel pump. They are not cheap. Do not use a cast iron pump because it is cheaper. It won't last more than 6 months, probably less.

    When the water heater starts leaking, replace it with a Mod-Con boiler and an indirect water heater. Protect the health and safety of you and any family you have living in the house.

    There is not one thing about that set-up that is safe or efficient. The only ones that gained were the hackaroos that installed it.

    They really are bad.
  • Eric_32
    Eric_32 Member Posts: 267
    Do you know....

    Do you know how many things are wrong with what you are trying to do there?

    The whole thing. You have a cast iron radiator full of God knows what in it, circulating thru your potable water line, and probably a cast iron circulator pump. Do yourself a favor, find another way to heat that radiator. That's a good way to get the family sick.
  • MechTech_2
    MechTech_2 Member Posts: 84

    the arrow on the volute of your pump, and ensure it's installed in the right direction. Your pump model has a bronze volute which is approved for open loop potable systems, but double check that the balance of your components are approved for potable applications.
  • icesailor
    icesailor Member Posts: 7,265
    Bronze Volutes:

    I had a Grundfoss with a brass volute and it wasn't flowing. Like this one is being described. The motor ran fine. My magnetic thingy said it was running. When I took the wet end out of the vulute, the impeller was inside and not connected to the motor.
  • Danger Here

    I see some potential issues with this type of system (using the heat from a DHW for a heating zone).

    1  Possible issues with thermal expansion.

    2. Most importantly, what happens in the summer when the heating zone is not seeing any flow for months?  The water will "die" and become toxic (that is why wet pipe fire sprinkler systems use backflow preventers).  This is nasty stuff and I would for sure stay away from it (I agree with the other posts on this).

    One last point, the older Armstrong circ was manufactured by Wilo, not Grundfos (note the steel terminal box).  Newer models of the Armstrong circs are no longer manufactured by Wilo...
  • Ironman
    Ironman Member Posts: 7,339

    I think we have a terminology problem here. The heading on the thread says "Hydronic Coil Air Haindler", but our O.P. discribes a "radiator" in his post. Could it be that he's improperly calling the hydronic coil a radiator and the responses have been based on the assumption that he's referring to a C.I. rad?

    I think what he's trying to ask is if the circ in the AHU is of sufficient size. The answer to that is an obvious "yes".


    Your problem is either that the coil is air bound, the check valve is stuck or the circ is bad.

    However, I would stronger add my voice to the others that you get the AHU off of your domestic and convert it to a closed loop. The type of setup that you have is illegal in most places and should be everywhere: it's a legoinella breeding machine.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • icesailor
    icesailor Member Posts: 7,265
    Air Handler:

    The problem is that the potable/domestic hot water heater is feeding a heating coil. At one time, it was absolutely prohibited. Lobbying by tract/spec building groups pushed this through over the objections of every plumbing board that I know of.

    Massachusetts allowed it with restrictions. One being that the copper in the coil or baseboard along with ALL piping had to meet potable water specifications. That means, Type "L" copper tube.

    This was a bad idea in the early 1960's. Every installation I ever saw, failed due to premature tank failure and the fact that you could never heat the structure with the water temperature used when it got cold. There wasn't room for any more radiation. The water turned rusty red, and the tanks started to leak.

    And that was before we knew about Legionella. There should be a big consumer warning on every install of this type.
  • Ironman
    Ironman Member Posts: 7,339
    I Totally Agree, Ice

    This is also posted on HVACTalk and on there he stated that it's in a condo in Vegas.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • nugs
    nugs Member Posts: 77
    Cross connection

    The plumbing code will not allow you to run potable water through a heating loop of any kind.  It is considered a cross connection and is illegal in all 50 states.
  • icesailor
    icesailor Member Posts: 7,265
    Combi units:

    Sadly Nugs, 'taint so.

    The AHJ's fought it but lobbying from the development and spec builders along with the few water heater manufacturers that went along, the legislature was lobbied, and the legislature made the boards go along. A good consumer idea, don't you know. In Massachusetts, the water heater tanks are supposed to be approved by the board. Plumbers don't install them. They are usually installed by HVAC guys who get a licensed plumber to get a permit for the plumbing part, if a permit is gotten.

    There are a lot of them out there. I think that all parts of the system are supposed to meet NSF conditions. I'm sure that a lot of Hackaroo installs don't meet that criteria.

    It has been mentioned that David Yates and someone else fought this hard. And failed. It shows how the rights of a few, get to screw so many and the few can get away with it.
This discussion has been closed.