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What's Best: Combi boiler or separate boilers?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by 4barrel, Aug 23, 2013.

  1. 4barrel

    4barrel New Member

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    Feb 15, 2013
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    I'm getting estimates for switching over to natural gas. I have had 3 plumbers recommend 3 different types of setups. First is a combi boiler, second is a condensing boiler with a condensing gas water heater, third is a cast iron boiler with a conventional gas hot water heater. My house is 1500 sq.ft, one bathroom, r-45 in the attic, energy star rated windows, no wall insulation, built i believe in the 1930's. My oil fired burner gives us endless hot water, only have to wait a few seconds to get it as well. I would like to continue that kind of performance. I have been reading on the internet combi boilers can be very troublesome, where the cast iron boilers last forever. Any experienced plumbers around? Which makes of boilers are the most reliable.

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  2. bbone

    bbone Member

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    Loc:
    Buchanan, New York
    4barrel I'm in the same boat combi boiler looks great but some guys say big problems can't wait to hear some replies
  3. 4barrel

    4barrel New Member

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    Why do you say a combi looks good. I have read that hot water can take a long time to reach the faucets, and they can suffer from low water pressure at the faucet when it is really cold out.
  4. bbone

    bbone Member

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    Loc:
    Buchanan, New York
    one box, lots of hot water,
  5. blades

    blades Minister of Fire

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    I would be looking at the mineral content of your water supply. Around here it is very high so those condensing units tend to plug up fast vs/ a traditional boiler for heat( steam or hot water) and a separate hot water heater again a traditional tank design.
  6. DAKSY

    DAKSY Patriot Guard Rider Staff Member

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    I moved this one over to the Boiler Room as it may get more visiblity there.
    Bob
  7. __dan

    __dan Feeling the Heat

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    Oct 5, 2011
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    Not plumber (an E1) but I install boilers for family.

    I put in the Weil McLain Ultra gas condensing boiler and Gold Plus indirect tank for my brother. That's the only way I would go, gas condensing boiler and indirect tank for DHW. I could go into the advantages but what will probably happen is that choice could add $1000 to your bids. Money well spent.

    If you want the three bidders bidding apples to apples, that's what I would do.
  8. heaterman

    heaterman Minister of Fire

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    Falmouth, Michigan
    When you say "combi" are you referring to the wall hungs with the integral hot water heat exchanger attached?

    If so look closely at the specs on it for GPM flow at list temperature rise? Some will list the flow rate at only 70-80* rise while others will show @100* , which is as it should be.

    Personally, I don't like them in applications where you may have more than a single hot water draw going on at the same time. Temp starts to fall off and they can be pretty restrictive as far a total flow available.

    With wall hungs in a residential application we always recommend installing an indirect tank. As far as getting hot water to you faucets is concerned, that's more a function of your plumbing rather than whatever is making your hot water. Install a hot water recirc if you must have instant hot water but they do waste a significant amount of energy.

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