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boiler always getting heat call

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t300
t300 Member Posts: 33
edited April 2 in Thermostats and Controls
Long sordid story. Triangle Tube Combi boiler. No name zone valves. mechanical relay box. half a dozen zones including radiant manifold in forced air furnace. Ecobee premium on the furnace, however electric elements of furnace never hooked up, the ecobee just called the furnace zone. I'm not a technician, know just enough to be dangerous so forgive what are probably some poor descriptions.

Problem. after some work including wiring changes, furnace zone is always getting a call for heat even with tstat disconnected.

- everything used to work fine.
- one of the NCOF zone valves was always bleeding glycol (not fully shutting), was going to replace in summer but then the Triangle boiler bypass/divertor valve failed so we had no furnace heat. tech put a dumb tstat on the furnace, wired up the electric elements and we waited for parts to come in. Triangle boiler was turned off. All was well.
- Since we already had system drained to replace boiler bypass valve, we replaced the leaking NCOF zone valve with a Caleffi Z111000. specs seem the same as the NCOF it replaced.
- some issues remembering how to wire the furnace back as it wasn't documented (not me!)

current state. everything back and running, all zones, except for furnace zone. Ecobee calls for heat and its zone valve opens and boiler gets a heat call as expected. Except that even when the Ecobee is NOT calling for heat, or ecobee completely disconnected; the zone valve open/closes as it should but there is still a heat call to the boiler somehow. Something off that furnace wiring appears to be calling for heat but can't figure out what. The other zones (floor heat) with their separate tstats all working fine.

Tried swapping relays, disconnected tstat, double checked wire connections, check relay box transformer. It must be either furnace miswired or Caleffi miswired but can't figure out what or where. Technicians coming back but they scratched their heads the previous couple trips and issue still the same so looking for some ideas.

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  • t300
    t300 Member Posts: 33
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  • Jamie Hall
    Jamie Hall Member Posts: 23,286
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    Ah... I'm a little confused. As I understand the way this should operate is that a thermostat calls for heat. The associated zone valve opens. The zone valve end switch -- or a relay in parallel with the zone valve (which is it?) closes, and the boiler fires up.

    Fair enough?

    Except that, again as I understand it, for the forced air furnace zone the zone valve opens and closes in response to the thermostat (that it's an Ecobee is probably irrelevant), but the boiler is always getting a call for heat regardless of the zone valve position?

    Now what is confusing is that "the boiler always getting a call for heat". It isn't clear to me whether the boiler is always getting a call for heat at all times, or only when the forced air furnace thermostat is calling, and you are saying that the position of the zone valve for that zone doesn't matter?

    So let me try to restate. You have six zones (I only see five relays. Why?). Now. All the thermostats are off. The boiler is off. The zone valves are closed. The circulating pump is off. You turn one, and only one, thermostat on. What, exactly, happens? Turn that one thermostat off. What, exactly, happens? Try this with all the zones individually.

    And please get back with the results...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • t300
    t300 Member Posts: 33
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    I guarantee I'm more confused that you lol.

    "Ah... I'm a little confused. As I understand the way this should operate is that a thermostat calls for heat. The associated zone valve opens. The zone valve end switch -- or a relay in parallel with the zone valve (which is it?) closes, and the boiler fires up."
    - my understanding of how its wired as well

    "Now what is confusing is that "the boiler always getting a call for heat". It isn't clear to me whether the boiler is always getting a call for heat at all times, or only when the forced air furnace thermostat is calling, and you are saying that the position of the zone valve for that zone doesn't matter?"

    - yes, the boiler is always getting a call for heat regardless of tstat and regardless of zone valve position. The relay for the furnace zone is always on (lit up). when I pull that specific relay, the call for heat stops. when I pull any of the other relays as a troubleshooting step, the furnace relay still stays energized.


    "So let me try to restate. You have six zones (I only see five relays. Why?). Now. All the thermostats are off. The boiler is off. The zone valves are closed. The circulating pump is off. You turn one, and only one, thermostat on. What, exactly, happens? Turn that one thermostat off. What, exactly, happens? Try this with all the zones individually."

    - actually 4 working zones plus DHW, so 5 relays. there are a couple more piped zones that previous owner did for 'future' but not implemented or wired up in any way.
    - Yes except with all the tstats off, including physically disconnecting the ecobee/furnace tstat, the relay for the furnace zone is still getting a call for heat If I pull that relay out then the heat call stops. Any other zone works as expected. The only thing that stops the call for heat on furnace zone is pulling the furnace zone relay.

    Now that I've stepped back from the trees to the see the forest, this should be a simple matter of tracing back all the wires on that furnace relay to see what is energizing it, and then figuring out why. What makes this difficult is the massive mess of wiring from the original installer, no documentation and even within the utility room they ran a lot of the wiring inside the wall as opposed to surface. Company is sending their controls electrician to review.
  • Jamie Hall
    Jamie Hall Member Posts: 23,286
    edited April 3
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    Progress. Maybe. Somewhere in the wiring to that specific relay coil it is getting power. Now just where that might be...

    As you say, that wiring is a bit of a jungle. Not unusual to see that on control wiring, but sad.

    My suggestion would be to go back to square one on that circuit. Disconnect ther wires to the misbehaving relay coil. Now... do you have a C wire to the Ecobee? One of the three wires? Then two other wires -- usually red and white, but remember that electricity is colour blind. The terminals these connect to on the Ecobee will be R and W. So far so good. Find the end of those three wires from the Ecobee in the junction box near the relay. Find the transformer powering the Ecobee -- the C wire from the Ecobee should be attached to one terminal. Now take a wire from that terminal of that transformer and connect to one of the relay coil terminals. Connect the wire from the W terminal of the Ecobee to the other relay coil terminal. Connect the wire from the R terminal of the Ecobee back to the other terminal (not the one with the C wire) of the transformer.

    That will work -- if the relay controls the zone valve. If the Ecobee controls the zone valve which in turn controls the relay, the idea is similar -- but not the same. The zone valve will have end switch terminals. You will treat those in a similar way to the Ecobee -- except that there's no C wire involved. You will go from one transformer terminal to one terminal on the zone valve end switch. Go from the other terminal on the end switch (I can't be more specific, as some zone valves have four terminals -- two for power and two for the end switch -- and some have three -- one for power, one common, and one for the end switch. If you have that arrangement, note what transformer terminal the common terminal is connected to and call that "C"). Where was I. Go from the other terminal of the end switch to one of the relay coil terminals. Go grom the other relay coil terminal back to the transformer and connect to whichever terminal did NOT get connected to the end switch.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    t300BillyWill
  • t300
    t300 Member Posts: 33
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    Thanks this is very helpful. Hopefully have good news to report in a day or 2. When I bought this house I had zero knowledge about any of this, been quite a learning curve.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
    edited April 3
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    So for clarity, You have 5 zones that are connected to a boiler.

    One of them is for a DHW tank.

    Three of them go to some type of radiators or convector or radiant system that does not require a fan to move the heat.

    The 5th zone is the problem zone. That zone is operated by Ecobee. If that is the case then, The Ecobee will signal the furnace to call for heat. In the furnace there is a “heat really” that normally activates the electric elements in the furnace.

    You probably don't want that to happen because you want the boiler water to heat a wet coil in the furnace. Once the wet coil is hot you then send a call for heat to that relay that is staying lit (Red LED).

    Your problem is in the way the Ecobee is connected to the furnace and the way the W wire from the ecobee is converting the signal from the furnace 24 VAC transformer (in the Green circle) to that Relay with the red light.

    Do you have the wiring diagram for the furnace? Can you post that wiring diagram? Since I do not see the Ecobee white wire connected to W1 on the furnace, I believe that the transformer from the furnace (Green Circle) is back-feeding the problem relay.

    The guy the took it apart should have taken a picture of the wires before disconnecting them.

    Those 5 relays should be powered by the 24 VAC transformer for the other 4 zones. Not the furnace 24 VAC transformer. You are lucky that you did not let the factory installed smoke out of one of those transformers or relays.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • t300
    t300 Member Posts: 33
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    The W from the (electric) furnace is not hooked up. Well it was temporarily to get heat while we waited for boiler parts but original wiring and now, it is not. The Ecobee W should be connected to the relay box or is it the zone valve first? What I don't get is why the call for heat even with the Ecobee physically disconnected. You have me thinking though of what else the original guy may have changed when he did the no heat call but maybe he did something else on the furnace
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
    edited April 3
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    So I guess I'm correct in my assessment. Ecobee to the Furnace and the 5 relays for the boiler zones. The 5 relays look like a site built system.

    I have connected many Hydro Coils in my career. There are several ways to do this. The easiest way is to add a "Heat Relay” at the air handler. The White wire from Ecobee will have a return path to the same transformer in the furnace. Then the dry contacts of the “heat relay” will operate the zone valve pump, boiler and relay, in the same way as the other wet zones do.

    What is probably happening now is the transformer in the furnace is feeding some electric current to one of the 5 relays that are connected to a different transformer for the other 4 zones. You may even have both transformers cross connected in the spaghetti of wires.

    Post the Electric Furnace Wiring diagram and we will figure this out.

    Here is an example of what I have done for other with fan coils that have add on hydronic coil. https://forum.heatinghelp.com/discussion/comment/1783726#Comment_1783726?


    In the pink shaded area is the heat relay that I added to make the boiler operate when his heat pump would not keep up with demand so the boiler would operate to get the system going at those colder temperatures. More sophisticated because it was a variable speed fan furnace.

    Your system should be less complicated. Please post the furnace diagram.

    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • t300
    t300 Member Posts: 33
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    Thanks Ed. Through trial and error found that with the HRV powered on, there is constant heat call to furnace boiler. With HRV unplugged from power, everything works as designed. Specifically when you plug in (power up) the HRV its fine for about 1 minute or so, then once the HRV spins up then the erroneous call for heat occurs. So must be something miswired in furnace when the original tech rewired to electric heat temporarily when my boiler failed. In any event a controls tech is here today to figure that out. I'll get the furnace wiring posted as it would still be great to configure this so the electric elements come on automatically in case the boiler fails as opposed to having to re-wire it every time. Or even a manual switch would suffice, I actually may like that idea better. Just not rewiring lol
  • Jamie Hall
    Jamie Hall Member Posts: 23,286
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    HRV? What HRV? You really do need someone to go over all the control wiring, assuming that nothing is correct, and get it connected properly. Has to be done in person...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EdTheHeaterMan
  • t300
    t300 Member Posts: 33
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    Good news sort of, system is back working. Long story short, the end switch on the new caleffi zone valve was DOA (or it got zapped during install). This was identified on a prior visit but I guess somehow the tech mixed up the DOA one and the spare. Replaced that and things are working again.

    Thanks for all the feedback here, brings to light how proper documentation and cleaning up the wiring needs to happen before future change. So now begins project to document all the wiring with the goal to make necessary changes for the electric furnace to become automated or semi-automated backup. As well as easier troubleshooting. thank you all.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
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    I like to draw wiring diagrams. I like to leave them with the customer when there is a particularly difficult or complicated wiring design. 3 copies, one is with the boiler or furnace next to the factory wiring diagram. I printed them on adhesive backed label paper that would fit in my laser printer. The other two on plane paper. That would be with the instruction manual that I left with the equipment. The other went in the file that the office held that included the contract to do the job with all the paid invoices. I would also make a second copy of the I/O manual that went in that same office file.

    That way you didn't need to get into the office to get the manual when doing service. I always hated it when someone ( mostly home owners) would take the manual from the boiler room to store it in a safe place, where no one could find it when I needed it.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • PRR
    PRR Member Posts: 126
    edited April 13
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    ...take the manual from the boiler room to store it in a safe place, where no one could find it when I needed it.

    Real Estate Brochure Box, screwed to the plenum. "Outdoor", to shed dust and drips. I have one on my furnace, need another for my water equipment.
    Most are over-priced. This one is under $10- https://realestatesupplystore.com/products/brochure-box-info-pack

    EdTheHeaterManDave Carpentier