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Condensing Boiler vs. conventional atmospheric burner type boiler

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Steve_210
Steve_210 Member Posts: 646
Hi Guys,
I have a client who has a townhouse that we are renovating right now. The original plan was condensing boiler which would only be heating (2) of the floors (tenant space is electric heat; 1 floor). Spray foam insulation everywhere; total of 1620 sq ft. Using all old radiators so everything should be well oversized (this is why a condensing boiler would've worked well) because of the lack of available chimneys, it looks like we are going to have to use a conventional atmospheric burner type boiler. My question is: For this amount of square footage, how much can he expect to save using over sized radiators? Hopefully, this makes sense. We are located in NYC with a design temperature of 10 degrees. I am just trying to give him the best possible advice. Thanks, Steve

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  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
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    What do you mean by 'lack of available chimneys'? Do you mean you have no place to properly vent the condensing boiler?
    I would try to get the mod con to work.

    There was an error rendering this rich post.

  • ChrisJ
    ChrisJ Member Posts: 15,929
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    Yeah,
    If there's a lack of chimneys, how does an atmospheric boiler work, but a modcon doesn't?

    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    JUGHNECanucker
  • jbo
    jbo Member Posts: 12
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    Aren't most mod cons able to side vent where atmospheric is a bit rare? If it isn't a closeted space you can usually just vent using pvc, exhaust clear and spaced to mfg specs and intake usually with a T close to the building in 'dead air' zone. (Should all be in IOM). I would think going atmospheric would be harder both in terms of avoiding short cycling and venting.
  • Steamhead
    Steamhead Member Posts: 17,012
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    jbo said:

    .......... you can usually just vent using pvc.............

    PVC is not UL approved for venting combustion products. Since there are now polypropylene-based and stainless-steel venting systems which are, there's no need to risk a failure or a lawsuit with PVC anymore.

    @Steve , can you clarify what venting locations are available? If there is no chimney, where were you planning to vent this thing?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • jbo
    jbo Member Posts: 12
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    @Steamhead This may have been updated but I thought UL-S636 certified PVC at 149*, and ANSI/ASTM D1785 allows it as well. Am I wrong in assuming it would not leave a contractor liable if both of those statements are factual and a boiler mfg' manual list PVC as an option? Also, are boiler mfgs leaving hemselves open to litigation to have PVC listed at all?
  • ChrisJ
    ChrisJ Member Posts: 15,929
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    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    kcoppZman
  • Robert O'Brien
    Robert O'Brien Member Posts: 3,548
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    NYC doesn't allow PVC for venting flue gas
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
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    If you can install an atmospheric, why can't you line the chimney with polypro or the like and use the mod/con? I've done that a few times.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • Steve_210
    Steve_210 Member Posts: 646
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    PVC is not allowed, Also Sidewall venting is not allowed unless you can gain 4 feet from the window, which we cannot achieve
    On 95% of our jobs, he has one water heater for the tenant and a new boiler with an indirect.
    There is an existing chimney liner,
    Original plan we were going to do fast n seal to the roof.
    We only have one chimney available so I have to common vent therefore we cannot use a condensing boiler.
    With the 2012 Energy code even an atmospheric gas boiler has to be 82% minimum aflue.
    I know it's hard but I was just wondering a rough estimate of how much more efficiency he could get from a condensing boiler it can be done but it would be a lot of extra expense and I don't know if it's worth it for the client.
  • JUGHNE
    JUGHNE Member Posts: 11,111
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    So what does California allow??
    They are on the bleeding edge of technology that the rest of the country has to eventually follow.
    We have all read the tags "The state of California has found this........etc" :*
    Solid_Fuel_Man
  • Gordy
    Gordy Member Posts: 9,546
    edited May 2017
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    You have to do a proper heat loss, and radiator edr survey to determine the necessary water temps. If then you could use say 140 supply with a 20 delta, and 120 return at design day. You would always be condensing with efficiency in the upper 80's at design and lower 90's above design conditions. Not to mention the benefits of odr, and not having to worry about sub 130 return to a ci boiler. Let alone a mixing valve additional cost to prevent that.

    As for your venting I'm a bit perplexed by your discription of options....
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,849
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    I believe "IPEX" makes the only PVC listed for gas venting (in areas where PVC venting is allowed)
  • Zman
    Zman Member Posts: 7,607
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    To answer the original question, if both boilers are properly sized and installed, I would say the efficiency difference would be somewhere in the 5%-10% range.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Gordyj a_2
  • kcopp
    kcopp Member Posts: 4,452
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    If the question is "how much will he save?"... I would have to think it would be in the 30-35% range. That is what I am seeing for most of my customers.


    Getting back to the clearance issue.... I thought that most all Cat 4 appliances that use an intake and exhaust, the clearance was 12" not 4'
  • Steamhead
    Steamhead Member Posts: 17,012
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    kcopp said:

    Getting back to the clearance issue.... I thought that most all Cat 4 appliances that use an intake and exhaust, the clearance was 12" not 4'

    Depends on what Codes are in force there. I'm assuming when he says-
    Steve said:

    PVC is not allowed, Also Sidewall venting is not allowed unless you can gain 4 feet from the window, which we cannot achieve

    that info comes from the local Code authorities.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Steve_210
    Steve_210 Member Posts: 646
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    I believe in Europe it's only 8 inches everywhere else in America it's 12 inches but New York City is 48".( it may also be New York) state.
    I spoke to a rep recently told me a story that he claims is the reason.
    Sometime after 9/11 a building had over 200 sidewall vent terminations. People seen all the condensate plumes
    And believing it to be smoke called the fire department, i'm told the law was brought in to avoid nuisance calls to the fire department. I don't know for sure if this is true but it would be interesting to find out.
    Thanks for the answers guys as far as efficiency is concerned it give me something to work on.
  • Steve_210
    Steve_210 Member Posts: 646
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    On the PVC issue we use this for make up air only never the exhaust because it's not legal here.
    Even if it was legal with all the information I got from here and other sources over the years I would not use it.
    I know there's been huge conversation about this in the past, that's my two cents.
  • Steve_210
    Steve_210 Member Posts: 646
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  • Steve_210
    Steve_210 Member Posts: 646
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    Another problem we're have on jobs because of the venting law