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Condensig boiler

airolds Member Posts: 2
Hi Guys,

My wife and I just purchased a home and we realized that the heating (specifically the boiler) system needs to be replaced. We currently have a hot water system (radiators) with a 50 year old boiler that moves the water simply by gravity... no pumping at all! I'd like to go high efficiency in order to take full advantage of the state rebates. I have received several offers and everybody but one guy (who seem very knowledgeable) is suggesting installing a condensing boiler.

I was convinced that a condensing boiler was the way to go but this last guy told me that condensing boiler will most likely **** the bed in 4-5 year and, on top of that, they require an expansive maintenance service every year (otherwise the warranty is voided). He suggests to instead install a less efficient boiler (85% efficiency) with constant circulation. His claim is that the boiler he wants to install does not require any sort of maintenance (or at least not every year), in addition he's claiming that he'll just hard code directly on the boiler the temperatures I want in the house in the morning and at night and I pretty much would not have to do anything from a controlling/thermostat point of view. He pretty much claims that the thermostat in the house would be useless at that point. I also told him m worry was that the pump constantly running would blow up my electricity bill and he said that, beside from the energy necessary to accelerate the pump at the right RPM, the pump once it's running does not use any energy due to gravity effect. Now, I called **** and that last claim but he insisted so much about it that I dropped it.

Finally he's also telling me that, although condensing boilers claim a 95% efficiency, they barely get at 90% in real application due to the returning water not being warm enough.

Although being an engineer and understanding technical concept very well I do not have a deep understanding on boilers and I am having a hard time understanding who's telling me the truth. The guys suggesting the condensing boiler or this last guy suggesting another type of boiler with lower efficiency but constant circulation? What do you guys think?

Also, is it possible / does it make sense to install a condensing boiler with constant circulation?

Thank you all for your help!



  • SWEI
    SWEI Member Posts: 7,356
    It's more than possible

    it's highly recommended.

    Where are you located?  Someone needs to do a room-by-room heat loss calculation and properly size your new boiler.  If you're lucky, the old radiators are oversized, which will allow lower water temperatures and higher efficiency from a mod/con boiler.  The good ones last for decades if properly installed.  Some need more maintenance than others.
  • airolds
    airolds Member Posts: 2
    Thanks! What about the last guy's opinion?


    Thanks for your answer. I will make sure to contact all the guys that gave mequotes about the possibility of using constant circulation.

    What are your thoughts on the opinions I got from that last guy I mentioned in my earlier post?

    I live in the Boston area.

  • SWEI
    SWEI Member Posts: 7,356
    Of "all the guys who gave me quotes"

    did any perform a proper room-by-room heat loss calculation?  The "last guy" seems to be at least partially informed, but you deserve a proper evaluation and design.

    There are a couple of pros who post here from the Boston suburbs.
  • Aaron_in_Maine
    Aaron_in_Maine Member Posts: 315
    Heat loss

    You need to have someone who measures and does a heat loss calculation. Also have them measure every radiator. Most gravity systems were oversized on radiation. I did a building up here in Maine that was gravity when it was built the heat loss was 179,000btu. The amount of radiation installed was 379,000btu. This building heats with 145 degree water on the coldest days of the year! Which also makes the boiler condense all the time. I get 96%eff every year when I check it.
    Aaron Hamilton Heating
    [email protected] yahoo.com
  • airolds2
    airolds2 Member Posts: 1
    Thanks for your advice, any thought on constant circulation?

    Hi Aaron,

    (had to change nickname 'cuz for some reasons I can't log into my account....)

    thanks for your answer. I will get a heat loss analysis soon. In the meantime, do you have any thoughts on the constant circulation? Somebody said they think I might end up with overheating... what do you think?

  • SWEI
    SWEI Member Posts: 7,356
    Constant circulation

    is highly recommended.  Outdoor reset control will prevent overheating, reduce noise, increase comfort, and save fuel.
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