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Old Weil McLain Gold CGt keeps not respecting thermostat

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LightArc
LightArc Member Posts: 5
in Gas Heating
Hey! My heat's been a thorn in my side for a long time, been trying to find a solution and someone recommended I ask here. Trying to figure out how to best proceed.

I have a Weil McLain Gold CGt in my basement, which uses natural gas and provides both heat (baseboard) to my unit as well as hot water. The trouble is, it frequently gets stuck in a permanently on or permanently off state. I'm in Massachusetts, and one of those is really bad depending on the time of year - When it gets permanently on in summer, my house will hit over 100 degrees, and in winter not having heat is really bad. I've bypassed this over the summer by just unplugging the circulator from the control board (so I can still have hot water, but not heat the house) but that's a temporary solution at best.

I've been told that this sounds like a control board issue, but we replaced that last year and it didn't solve the problem.

What does seem to solve it, at least temporarily, is replacing the 3-way valve. It's the little gray box at the top-left of the image attached. Repair people have replaced it a few times, saying that it broke and got stuck in an on or off position - But they also have told me that the part's getting harder to find, and each time they've replaced it, it's been to the tune of $400 or so after parts and labor. It inevitably breaks again within a few months (sometimes weeks, and I'm back at square one.

I've looked into replacing the boiler entirely, having trouble finding a contractor who isn't looking to rip me off or sell me something much bigger than what I need. But I've also had a few people tell me that the problem with my existing one should be solveable, and that I should ask here.

Any thoughts on fixing this issue? Or am I better off replacing it?


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  • Jamie Hall
    Jamie Hall Member Posts: 23,286
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    There's no point in replacing anything -- valve or boiler or anything else -- until you find out why that valve isn't working properly. It may be a water quality issue, or a bad sensor, or a control board issue, or simply a loose connection, or... but whatever, the valve isn't the cause, it's the symptom -- and curing the symptom doesn't fix the cause.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • LightArc
    LightArc Member Posts: 5
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    Jamie Hall said:

    There's no point in replacing anything -- valve or boiler or anything else -- until you find out why that valve isn't working properly. It may be a water quality issue, or a bad sensor, or a control board issue, or simply a loose connection, or... but whatever, the valve isn't the cause, it's the symptom -- and curing the symptom doesn't fix the cause.

    I have square-zero knowledge on how to start figuring that out, and everyone I've brought in to look at it has said one of three things:
    1. It's the control board (we replaced it already)
    2. Replace the valve and you should be fine (we've done that 5 or 6 times now)
    3. This boiler's too old to be worth spending time digging into why this keeps happening
    So far I haven't been able to convince anyone to *spend time actually looking into why it's happening*, and while I've learned a lot in the dozens of hours I've tried to figure it out myself, I'm not exactly an expert. :frowning:
  • Jamie Hall
    Jamie Hall Member Posts: 23,286
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    In response to...
    1. A fairly normal parts changer's response. Didn't fix the problem. Wasn't likely to. He or she doesn't know how to find out what the problem was.
    2. Another parts changer's response. May have "fixed" the issure temporarily -- but those valves are intended to last years, not months, unless there is something else wrong.
    3. That boiler is still in production. The guy doesn't know how to troubleshoot it, so he wants to sell you something which maybe he does understand (and maybe not).

    Bottom line: you need a technician out there to come and find out what the problem really is, and fix it. Such people do exist. Where are you located? Perhaps we know someone nearby we can trust...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • LightArc
    LightArc Member Posts: 5
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    Jamie Hall said:
    Where are you located? Perhaps we know someone nearby we can trust...
    That'd be great! I'm in Norwood, MA, just outside of Boston.

  • Jamie Hall
    Jamie Hall Member Posts: 23,286
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    Try Ryan, at New England Steamwork (401) 954-3510. He usually does steam, but he -- and his team -- can do almost anything, and I know him to be one of the very best in the business.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    ethicalpaul
  • LightArc
    LightArc Member Posts: 5
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    Jamie Hall said:

    Try Ryan, at New England Steamwork (401) 954-3510. He usually does steam, but he -- and his team -- can do almost anything, and I know him to be one of the very best in the business.

    Thanks, I'll give him a call tomorrow!
  • LightArc
    LightArc Member Posts: 5
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    No luck, unfortunately - they told me they won't come out for a gas boiler, and recommended me to someone else (Gas Doctor, in Providence) - but they won't come out to Norwood. 
  • ethicalpaul
    ethicalpaul Member Posts: 5,702
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    Won’t come out for a gas boiler? That sounds really strange!!
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
  • Tim McElwain
    Tim McElwain Member Posts: 4,621
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    Try Denny Reardon at e-mail address dennys.service@yahoo.com tell him I gave you his information. I will try and find a phone number for him and come back and post it.
  • Tim McElwain
    Tim McElwain Member Posts: 4,621
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    Dennys Service is in Peabody Mass and his number is 978-531-4010. He is one of the best!
  • JohnnyB201
    JohnnyB201 Member Posts: 1
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    I have installed 2 of these CGt boilers and both have the same problem. The cartridge for the 3 way zone valve gets stuck in either the open or closed position. Weil McLain sells just the cartridge VCZZ6100/U for about $40. It will keep happening though. Weil McLain has discontinued this boiler after only a short time selling them. Obviously they're well aware of the issues. I've tried treating the water in multiple ways and still end up with the same problem eventually. This style boiler (hot water with a coil) was a great idea for weil McLain especially for small apartments but it was terrible design. The 3 way zone valve is just awful.
  • mattmia2
    mattmia2 Member Posts: 9,639
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    Maybe pull the cartridge out and soak it in some citric acid or vinegar once a year?

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