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Thread: Hot coming out of cold... Boilermate/Coil issue?

  1. #16
    DIY Member watson524's Avatar
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    wow ok... lots to think about, or at least ask about since i'm not quite sure what it all means but i think i get the general idea.

    We actually don't have a chimney. The stainless piping off the boiler goes to a power venter and a "squirrel trap" right at the bottom of the siding there.

    The oil company is coming Friday to look at things so we'll see. One interesting thing I noticed is that the cold pipe from the coil that goes to the boilermate and the house line is actually very warm even over where it goes into the boilermate. Not HOT, and i can hold my hand on it but it's not cold like you'd expect. Seems like something is definitely out of balance and migrating to where it shouldn't.

  2. #17
    DIY Member watson524's Avatar
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    Well the oil company guy that put the thing in came.... He was one of the ones that installed the boilermate. He said they leave the coils in for a backup system in case the boilermate goes BUT.... said that either the hot or cold valve near the coil should be shut off but shutting the hot off was better. Ok, I get it, now there's no way to have hot coming from the coil BUT I asked him all kinds of questions about if cold is going in, hot isn't coming out, do I need to worry about steam, pressure, condensation, etc? He said no. Also, he opened the mixing valve between the hot and cold there just aboute the aquastat about 1/8 turn and said the well tank would maintain the pressure in the system.... and by then I was starting to get suspect. Ok, so I ran hot water, which was hot but not steaming and since hot valve out of coil is closed, obviously it can only come from the boilermate which is the desired outcome but I went down a bit after he left because I'm still scratching my head, and guess what, as I expected.... the line above the valve on the cold side of the coil (which goes up to the boilermate and out to DCW is starting to get warm, and below the valve from the cold in to the coil is REALLY warm.... so I suspect since the hot side of the coil has no where to go, and since the boiler is firing because of calls for heat, obviously the water sitting in there will warm up and I think it's going backwards a bit into the cold side. Does that make "sense"? Sense in the fact that is what is happening, but maybe not what SHOULD be happening.

    He also said that yeah he might be able to take a wire off the aquastat and just have the high limit but he said it also could have high and low turned back a bit but only took it back to 150/170..... Said low could be set to 110 as the lowest but then I said "well is that enough to have for hot water baseboard???" and so 150 is the low, 170 the high....

    Oy... I mean it's nice that now we only get DHW from the boilermate and I guess the theory is nice that if the boilermate dies, I can easily go back to DHW on the coil but I think in practice this isn't the right thing.....

  3. #18
    In the trades Dana's Avatar
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    Quote Originally Posted by watson524 View Post
    wow ok... lots to think about, or at least ask about since i'm not quite sure what it all means but i think i get the general idea.

    We actually don't have a chimney. The stainless piping off the boiler goes to a power venter and a "squirrel trap" right at the bottom of the siding there.

    The oil company is coming Friday to look at things so we'll see. One interesting thing I noticed is that the cold pipe from the coil that goes to the boilermate and the house line is actually very warm even over where it goes into the boilermate. Not HOT, and i can hold my hand on it but it's not cold like you'd expect. Seems like something is definitely out of balance and migrating to where it shouldn't.
    Power vented through stainless flue condensation is less of an issue, but keep an eye out for black acidic drips burning through your galvanized sections when turning the boiler temp down.

    If the embedded coil is anywhere in the loop it's just plain WRONG, now that you have an indirect, as is maintaining the boiler's low limit at 160F. The high standby temp of the boiler is just ROBBING you of the efficiency gains that you'd otherwise be reaping with an indirect.

    Even without retrofit smart-controls, setting the low limit to 140F and letting it cycle between 140F & 180F would only drop the average temp to the radiation from ~170F to ~160F, but it would cut the number of cycles required to acheive the same average duty cycle (== same heat output for less wear & tear on the boiler.) With the "dumb" controls the boiler is parked at the high-limit at the end of a burn cycle, but with heat-purging controls managing the burn it leaves the boiler near the low limit at the end of a cycle, which cuts standby loss considerably. Low double-digit percentage fuel use reductions are typical, but with 5x oversized boilers (all too common) savings can be in the 20-30% range, sometimes more.

  4. #19
    In the trades Dana's Avatar
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    Quote Originally Posted by watson524 View Post

    He also said that yeah he might be able to take a wire off the aquastat and just have the high limit but he said it also could have high and low turned back a bit but only took it back to 150/170..... Said low could be set to 110 as the lowest but then I said "well is that enough to have for hot water baseboard???" and so 150 is the low, 170 the high....

    Oy... I mean it's nice that now we only get DHW from the boilermate and I guess the theory is nice that if the boilermate dies, I can easily go back to DHW on the coil but I think in practice this isn't the right thing.....
    I think you need a second opinion- this guy seemed more interested in not actually doing anything than actually diagonosing & fixing a problem.

    110F as an operating low-limit is too low- you're likely to damage the heat exchangers by too much time spent operating at that temp with the circulation pumps running. It would still work with your baseboards though, as long as the high-limit was 160F+, since the boiler temp woiuld rise fairly quickly to where the baseboards are starting to put out significant heat, and rising more slowly as the heat-emittance increases further. But even at 130F out the baseboards would be emitting ~250BTU/foot, and the return water would be well into condensing temps under 120F, potentially creating a severe condensation issue. The condensing temp of undiluted boiler exhuast is typically in the ~130F range- (well above that of natural-gas exhuast which is usually ~122-125F). The manufacturer's warranty on the boiler would be void in that mode of operation. At a 140F low-limit and a high-limit north of 170F you'll be OK. Every 10F you can peel off the average boiler temp is worth ~ 2-3% fuel savings, unless you set the high & low so close together that it short-cycles.

    See if you can't find somebody willing to set it up for cold-starting and installing an Intellicon 3250 HW+, and disconnect the coil. For reasonably handy people installing and tweaking in one of these is a reasonable DIY project. See the manual. They're available from a number of online sources for under $250- sometimes under $150 on auction sites or webstore sales.

    With an Intellicon you set the existing boiler controls up for cold starting, set the high-limit to the max operating temp specified by the boiler manufacturer, set the operating low limit (during active calls for heat) to 140F and let the controller "learn" how soon to turn off the the burner in anticipation of the end of the thermostat or indirect HW tank call to be able to simply park the beast at lower temp rather than keeping it hot in anticipation of a heating or indirect HW call that's not actually coming for hours/days/weeks. (As a DIY you'd have to figure out how to set up the boiler for cold start by consulting the boiler or controller manufacturer's documentation.)

    In the meantime you might try closing the valve to the embedded coil on the COLD feed side, and opening up the hot valve, if you insist on keeping it for backup- it doesn't seem likely to increase the standby loss an more than it's already doing. I'd just cut it out of the HW heating system, myself- the odds you'd ever need it and be able to actually use it are low, and in the meantime it's just a headache and a heat drain out of your boiler burning extra oil for no good reason.

  5. #20
    DIY Member watson524's Avatar
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    Thanks for all the info! I'm running around trying to get some things done for a trip tomorrow so I need to look at this again when I have more time to digest it but one question I did have.... can you tell me why you think I should close the valve to the coil on the cold feed side vs how he did it today with the hot output side being closed? I just want to understand if one side would matter more though honestly, closing the cold I THINK makes more sense to me just in that if there's cold going in, getting hot and having no place to go on the output/hot side, that seems like asking for trouble to me. Vs if the cold is in closed but hot out is opened, it'll just kinda sit there in "equilibrium" so to speak with no pressure build. But again, what do I know LOL! :-)

  6. #21
    DIY Member watson524's Avatar
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    Hi all,

    I'm reviving this one because our AC/heat pump company came to take a look while they were doing spring start up on that system last week. they said leaving the coil in is perfectly acceptable but that it would be better to close both hot out of coil and cold coming in and I shouldn't need to worry about any boil off or anything (the tech said his mother has had the same setup for 15 years after she added an amtrol tank to the system).

    He did say however that it was silly to have the boiler running when nothing needs it and recommended changing the aquastat (mentioned a honeywell 8148A) and setting it up for cold start so that unless a zone (hot water baseboard or hot water amtrol tank) is calling for it, the boiler won't run at all.

    Based on feedback, it sounds like some of you might not agree with the first part (leaving the coil in) but would agree with the cold start of the boiler, right? Is there anything so bad with this proposed setup?

    One thing I don't get is let's say that the boilermate dies one day. I can close the valves to/from the boilermate off, and open the ones to/from the coil, but since potable hot water isn't a zone (unless it's coming from the boilermate), then I don't think the coil will make hot water in a cold start setup because there won't be a zone calling to turn it on, right?

  7. #22
    Retired Defense Industry Engineer jadnashua's Avatar
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    Most indirects will outlast the boiler firing them, so it failing is generally not something you have to worry about. If you change the aquastat to cold start, then you'd have to change it back to use the internal coil. Personally, I wouldn't worry about it and disconnect it.

    Regular cold starting, especially if it is a short cycle, can be problematic on a boiler. But, the burn time to reheat the indirect should be long enough to not be a big problem, then, it likely wouldn't need to come on again for quite awhile (most indirects have decent insulation, and you may only need to crank it up once a day, if your heavy use is in the morning for showers.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  8. #23
    DIY Member watson524's Avatar
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    What about in the winter when our heat pump can't keep up and we're using the hot water baseboard. The tech said they'd set the temp at 180 because you need that for the hot water baseboard system coming back in but so I need to worry about short cycling if say a heat zone called for it?

  9. #24
    In the Trades Tom Sawyer's Avatar
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    Yes, cold start the boiler and disconnect the coil. As for the aquastat I'm gonna assume you have an L8124 on there and a knowlegable tech knows how to disable the low limit so's you don't need to buy a new one. BTW, a Beckett Heat manager or similar product will save you quite a few more bucks as well. Google it.

  10. #25
    DIY Member watson524's Avatar
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    They're saying leave the coil in place, just shut off the cold valve going to it and the hot coming out of it vs taking it out and getting a plate.

    And I did ask them about just disabling the low limit on the existing aquastat (I'm not sure which one it is but if it's written on it somewhere I can look) and he said he's seen that done several times and twice it failed after about 6 months but didn't say why. Now I'm wondering if I really should have them do it or what. Anyone from NE PA on here that has a clue and makes house calls?

  11. #26
    In the Trades Tom Sawyer's Avatar
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    Yes, leave the coil in place, just shut it off. The low limit is just a switch that makes on temperature drop. There is no reason why disabling it would cause anything to fail. I have disabled a few dozen or more over the years, none have failed because of it.

  12. #27
    DIY Member watson524's Avatar
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    But not something I could do myself? Just seems silly to spend $277 for part and install (though it's not THAT much in the grand scheme of home maintenance) when what I have is perfectly capable of doing what the new part will.

  13. #28
    Retired Defense Industry Engineer jadnashua's Avatar
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    During the heating season, when the boiler may need to run frequently, you would probably want the low-limit functioning. Once you figure out which wire it is, you could just put a switch on it (toggle switch, wall switch, whatever as it's low-voltage and not much current, most any switch would work), and close it during the heating season, and open it the rest of the year.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  14. #29
    DIY Member watson524's Avatar
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    oh wow..... well now we're into a whole 'nother realm. new england huh... want to take a nice trip right down 84? i'm 5 minutes off the exit in PA :-)

    i'm totally torn on what to do at this point because i can't seem to find anyone down here that can give me a straight answer. anyone know anyone in PA?

  15. #30
    In the Trades Tom Sawyer's Avatar
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    Take the cover off, take a good picture and post it and I'll tell you which wire to cut and cap.

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