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Boiler help

warinhavwarinhav Member Posts: 4
edited October 17 in Controls
We just had a Weil-McLain boiler installed with a Taco ZVC406-4 zone valve control. We paid $ plus for the boiler and installation. The problem is slow heat. Doing a little research online, I came to the conclusion the circulator pump isn't working. So we called the plumber who installed it. I told him what I thought the problem was and we went back and forth on it. He insists "The circulator pump has to be working or we wouldn't have any hot water at our taps." I told him I thought that was wrong, the hot water at the taps would work because of town water pressure. After coming here twice, he insists its working and said he doesn't know how to explain it to me so I'd understand..!
This morning I took my multimeter downstairs and disconnected the pump. I turned on our heat and hot water and checked the wires. No voltage. I took the cover off the panel and tested where the wires connect. No power. There is a little transparent relay just above the panel connection point. If I turn the power off to the whole system and turn it back on, the relay clicks and you can see it making contact but no power to the leads.
So what do you think? Is that relay bad even though it engages? Money is tight so I'd like to fix it myself. Any advice would be appreciated. Thanks


  • hvacfreak2hvacfreak2 Member Posts: 491
    I would power the pump from the supply voltage to the boiler ( it will run continuously ). Once you can see the difference I would drag the plumber by his ear down to the basement to show him the difference ( no voltage from the relay ). The plumber needs to replace that relay.

    Mechanical Enthusiast

    Burnham MST 396 , 60 oz gauge , Tigerloop , Firomatic Check Valve , Mcdonnell Miller 67 lwco , Danfoss RA2k TRV's

    Easyio FG20 Controller

  • Can you show us a picture of how the ZVC406 is wired?
    Often wrong, never in doubt.

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  • MaxMercyMaxMercy Member Posts: 17
    edited October 17
    warinhav said:

    So what do you think? Is that relay bad even though it engages? Money is tight so I'd like to fix it myself.

    You shouldn't have to pay to fix it. If you paid a professional (he is, right?), then he should make sure it's working.

    You don't need to disconnect any wiring. When the zone is calling, the circulator should have 120V across the black and white wires. You can check this at the circulator or across the terminals.

    It looks like the relays are dry contacts. The circulator is hard wired to the neutral and the hot is switched by the dry contacts on the Taco. If no hot is wired into the right spot, the relay won't switch any power.


    EDIT: Trying to figure out if the installer thought you wouldn't know that the domestic hot water flow is "powered" by city water pressure or if he really thinks the circulator does that.

  • kcoppkcopp Member Posts: 3,535
    What model Weil boiler is it? Is it possible the system has an outdoor reset function and that the temps are on the mild side thereby producing lower temp heating water output to the system?
  • EdTheHeaterManEdTheHeaterMan Member Posts: 798
    edited October 18
    How many circulators? Does it have only one circ pump? The ZVC may not be the control operating the pump. The pump may be operated by the boiler control.

    The best way to see if the circ pump is getting power, measure the voltage at the pump!

    ZVC has multiple wiring options for things like Primary/Secondary piping design with 2 pumps. Your control may not be set up to operate the pump.

    If your Control IS set up to operate the pump, then the wiring may not be completed properly.

    Take some pictures on your phone, then email than to yourself so you can upload them to your computer. (that's how I do it) once you have them in a file on your computer it is easy to post them

    We would like to see the wiring inside the ZVC box and the boiler piping from about 6 to 8 feet away. At least 2 angles of the boiler
  • warinhavwarinhav Member Posts: 4
    Thanks for all the help guys. I found an old iron down cellar and cut off the cord and hard wired the circulator pump, just as a test. It came on instantly and we had heat immediately. I'm going to put everything back the way they left it. I'm going to call the electrician first to see what when he can come out. I haven't dealt with him yet and I'm anxious to see what he says. I'll take some pics and try to post them. not sure if it'll work. Thanks Hvacfreak. MaxMercy...The way he was speaking, he absolutely believes the circulator controls the domestic flow. He is licensed.? kcopp..I don't think so.. Edtheheaterman...The circulator is hard wired directly to the board. one pump. Im gonna try the picture thing..

  • warinhavwarinhav Member Posts: 4

    The second pic is where the circulator is connected.
  • EdTheHeaterManEdTheHeaterMan Member Posts: 798
    edited October 18
    The problem is where the pump is wired. The black wire on the pump and the white wire on the pump are both connected to a switch. There is no power coming from the switch. There is a symbol just above the terminal screws indicating just that.

    Ask your electrician to put the white wire from the pump on N anywhere on the control, then a wire from L1on the control and place it on the terminal where the white wire from the pump was removed.

    Illustration fo follow:
  • EdTheHeaterManEdTheHeaterMan Member Posts: 798
    edited October 18

    Here is the suggested wiring from Taco:

    I have indicated the problem spot in green. Have your electrician do this and send the bill to your installer. Include a letter addressed to the state attorney generals office (if there is a division that handles plumbing license address it to that department) and ask if the contractor wants to pay for his mistake and learn from it, or does he want his license questioned? What is his license worth to him and is it worth the hassle. Include this illustration with your letter and say "Your Welcome" for the lesson on wiring.

    Either way, I would NOT send the letter to the AG's office I would just use it to let your installer you are serious about his admitting his mistake and owning the results of his error.

    BTW: If you are at all handy and are comfortable with electricity, this is a DIY thing for many.
  • MaxMercyMaxMercy Member Posts: 17

    Exactly. He connected the circ to dry contacts. The X X contacts on that zone controller only switch what they're fed.

  • warinhavwarinhav Member Posts: 4
    You guys are great. I wasn't sure exactly what you meant to do Ed, but I went to youtube and there was a step by step video. Rigged it up and instant heat. This is great. I don't have to deal with the morons who installed it. It's Sunday, the wife is at work, football is coming on, and we have heat! Thanks again everyone. God Bless.
    Alan (California Radiant) ForbesZmanMaxMercymikeapolis
  • Tom_133Tom_133 Member Posts: 702
    Good eye Ed, that dry contact seems to get a lot of guys in trouble!!
    Montpelier Vt
  • JohnNYJohnNY Member Posts: 2,494
    Tom_133 said:

    Good eye Ed, that dry contact seems to get a lot of guys in trouble!!

    Meanwhile, that dry contact is a godsend and typically underutilized.
    For troubleshooting and private consulting services, find John "JohnNY" Cataneo here at :
    "72°F Mechanical, LLC"
    Or email John at [email protected]
    John is the Boilers and Hydronic Heating Systems Course Instructor at NYC's Mechanics Institute, a professional Master Plumber, licensed by The Department of Buildings of The City of New York, and works extensively in NYC while consulting for clients in and out of state.
    For residential service and installations in New Jersey, please see Toro Plumbing & Mechanical and fill out our contacts page, upload pics, and submit, or call (973-672-1000).
    Alan (California Radiant) Forbes
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