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Thread: Oil fired boiler tankless coil problems??

  1. #1

    Default Oil fired boiler tankless coil problems??

    Need help/advice,

    I have come to the conclusion that i will install an electric hot water heater to take over my demands in the spring i- but it is the dead of winter and need advice. My hot water only lasts a few minutes in the shower, but seems well at all other faucets. I live in New Jersey. I have 2 Delta Monitor fixtures in my bathroom (bath & shower separate). I have researched all about tankless coils and mine probably should be replaced. I may attempt it myself or call a pro to do it, but:

    1. If i do decide to switch to Electric HWH is it worth the effort to replace the coil. (i did read about keeping the coil in series with the new HWH and cutting off the boiler in the summer)? If i don't replace the coil and it is clogged or just insufficient, how will it affect the new electric hot water tank when it is installed?

    2. Could it just be my aquastat settings (Hi 180 lo 150 diff 15)?

    3. I did recently replace the shower head to a higher flow unit. Could this cause problems with the anti-scald balancing valves in the Delta fixtures?

    4. If things really go good for me i want to change my entire boiler next year. Does this change any of the things i want to do?

    5. I couldn't get much info off the boiler, but the serial plate tag stated IBR model 1352.

    Any advice would be appreciated!!

    Thanks,

    daves

  2. #2
    Network Engineer rmelo99's Avatar
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    Electric hot water heaters are on the expensive side to run and recovery isn't that good. So if you are looking to get a seperate unit that isn't gas I'll assume it isn't available at your home. If it is then that is a much better option.

    You have plans to replace the boiler, if that is true than a new boiler with an indirect water heater will make you plenty of hot water to keep you happy. It was be a waste of money to buy a seperate tank to use only for one year.

    It sounds like your coil is showing it's age and just not producing as much hot water as quick as you need. It doesn't help that you added a higher flowing shower head. That will easily cut the length of time you get hot water(water flows from shower faster than the coil can bring it up to temp.)

    I wouldn't mess with your aquastat just yet, esp since you seemed to have explained some of the possible culprits.

    The plate off the boiler is just a rating and means nothing to anyone who doesn't have the big picture of your whole house.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    An in-boiler coil is a type of tankless WH. Cold comes in, gets heated by passing through the coils in the hot water bath (instead of a flame), then goes to your fixtures. So, it must be working as you said your sinks have hot when you need it. The new high volume showerhead is your main culprit...you are drawing too much water through the coil and it can't provide enough heat. It's sort of like passing your hand across a candle. Do it slowly, you could get burned, do it fast, and you probably won't notice. By drawing more water than can the thing can heat fast enough, you're doing the same thing - only getting warm water. Switch back to a standard showerhead until you replace the boiler next year. then, pick an indirect WH. This is essentially a tank with a coil in it fed by the boiler...sort of like a radiator zone.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4
    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by daves View Post
    1. If i do decide to switch to Electric HWH is it worth the effort to replace the coil. (i did read about keeping the coil in series with the new HWH and cutting off the boiler in the summer)? If i don't replace the coil and it is clogged or just insufficient, how will it affect the new electric hot water tank when it is installed?

    2. Could it just be my aquastat settings (Hi 180 lo 150 diff 15)?

    3. I did recently replace the shower head to a higher flow unit. Could this cause problems with the anti-scald balancing valves in the Delta fixtures?

    4. If things really go good for me i want to change my entire boiler next year. Does this change any of the things i want to do?

    5. I couldn't get much info off the boiler, but the serial plate tag stated IBR model 1352.

    Any advice would be appreciated!!

    Thanks,

    daves
    1. Sure it is if you have no hot water.....

    2. Those settings are just fine. What are the settings on your indirect tank? What are you having the domestic water heated up to?

    3. It shouldn't and if everything in your coil is working properly you should beable to provide water to run that shower for quite a while without problems.

    4. Having a boiler heat up your domestic hotwater is great in the winter when your boiler is going already. However in the summer you're heating the water with a pretty large input appliance VS a 30-40,000 BTU hot water tank.

    5. No worries.
    Last edited by Doherty Plumbing; 12-13-2009 at 03:00 PM.

  5. #5
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    #1 you are probably running out of hot water for one of the following reasons

    1 - Tempering valve element is shot
    2 - Too much flow through the coil (they are only rated at between 2 1/2 gpm and perhaps 4 if its a big assed coil
    3 - The coil is limed up

    I would expect # 3

    Tankless coils are possibly the least efficient way to make hot water as it requires the boiler to maintain constant temperature all year round.

    electric water heaters suck also.

    Look into an indirect like a Super Stor or a Boler Mate

  6. #6
    DIY Junior Member MAoilTech's Avatar
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    Agree's with peter

  7. #7
    In the trades Dana's Avatar
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    Quote Originally Posted by Peter Griffin View Post
    #1 you are probably running out of hot water for one of the following reasons

    1 - Tempering valve element is shot
    2 - Too much flow through the coil (they are only rated at between 2 1/2 gpm and perhaps 4 if its a big assed coil
    3 - The coil is limed up

    I would expect # 3

    Tankless coils are possibly the least efficient way to make hot water as it requires the boiler to maintain constant temperature all year round.

    electric water heaters suck also.

    Look into an indirect like a Super Stor or a Boler Mate
    What he said, 'ceptin' before you buy the indirect, verify that your boiler isn't oversized for the heating load. If it is, go with a reverse-indirect (it's more money, but bear with me) like a TurboMax or Everhot EA series, ErgoMax, and replumb the heating system a bit to use the reverse-indirect as a buffer for the heating season. If your boiler is more than 2x oversized for the heating load (which is WAY too common), you'll reap double-digit percentage fuel savings during the heating season due to the buffering effect of the thermal mass of the tank. (A standard indirect will provide some benefit too, but not even half as much.)

    To find out how oversized the boiler is, read the ratings on the nameplate, and plug 'em into the calculator downloadable here (along with the other relevant information, including location or heating degree-day & fuel use ratio.):

    http://www.nora-oilheat.org/site20/index.mv?screen=home

    http://nora-oilheat.org/site20/fsa/F...or_1_1_0_8.zip

    If it's under 1.5x oversized it'll still improve things, but sub-10%. At 1.25x oversized, stick with a standard indirect and zone it as "priority zone".

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    Agreeing with Dana.

  9. #9
    In the trades Dana's Avatar
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    As an aside, a reverse-indirect's heat exchanger is very much like the internal coil on a high mass boiler, only much much bigger, which gives you better flow.

    The mass of a reverse-indirect is also several times that of a high-mass boiler, but it's insulation tends to be much higher than the boiler (and can be made arbitrarily high with additional insulation, if you like), and without flues & fireboxes as heat-loss points, the standby losses are extremely low- lower than any boiler, and much lower than a standalone tank.

    They'll outlast any standalone tank, and most tankless heaters too, with minimal maintenance.

    As long as your boiler is still happy with cold starts (and most are these days), as long as the indirect is maintained at 140F or higher the wear & tear on the boiler from DHW burns are minimal- much lower than the shorter & more numerous cycles you get when using the internal HW coil. If you run it at 120F you'll still have plenty of hot water, but the cooler return water can cause condensation & corrosion issues on the boiler's heat exchangers, reducing both efficiency & lifespan.

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