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  1. #1
    Join Date
    Nov 2012
    Location
    Hubbardston, MA
    Posts
    2

    Cordwood boilers, radiant floor heat

    Hi - We are in the process of completing an addition on an old farm house (main house is 190yrs old) in central Massachusetts. The existing house is approx 1500sqft, somewhat drafty, with one zone of forced hot water baseboard heat supplemented by a wood cookstove. The extension is still in progress but will be approx 1200sqft, modern construction, with four zones of radiant floor heat (pex on plates under subfloor, not in concrete). I'm not thrilled with the baseboard heaters, but I'm not renovating the existing house right now.

    The existing heat is on an oil boiler, marked as 112,000BTU/hr, with a domestic hot water coil, tankless. I think the baseboard heaters are hooked up wrong, because the domestic hot water coil only provides a decent level hot water (both temperature and quantity) so long as the baseboard heat is cranked up, and the baseboard heaters all get hot whenever the boiler is running all year round. Even in New England, in a drafty old house, our oil use in the summer isn't a whole lot less than the winter. Yeah, we have the wood cookstove going a lot in the winter, but that still seems off.

    Are the tankless boilers like that just super inefficient for domestic hot water? Can we add a tank? Can we run both the baseboards and the radiant floor heat off of that, and actually be able to take a hot shower occasionally?

    If I do need a new boiler, I'd really love to get a nice cordwood gassification boiler. Cordwood is nearly free for us, and besides I just like wood. But the boilers we've seen so far (Tarm, in New Hampshire) are not in the budget right now, especially with the recommended tank. Besides, I don't know if is it really reasonable to use a cordwood boiler for domestic hot water year round, even though I know some folks do.

    Someone suggested that with a wood boiler, I'm better off using the existing boiler for domestic hot water and only firing up the wood boiler when we need heat. But the existing boiler is terrible for domestic hot water!

    I've had trouble finding an HVAC guy out here who knows anything about radiant floor heat or the high-efficiency wood boilers, so any advice would be appreciated.

    Thanks.

    Joshua

  2. #2
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,741
    i would want a indirect tank added for domestic hot water set up with its zone also would make it the priority zone . if the house is leaky you could save alot be sealing it up. depending on how the system is piped might need to be repiped with a new zone system and new pumps
    We really need change now

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,370
    Sounds like you have a control issue with your boiler.

    A good radiant guy would know how to use your current boiler for radiant. Use the Locator map link in my sig and see if any of us are in your area.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  4. #4
    Join Date
    Nov 2012
    Location
    Hubbardston, MA
    Posts
    2
    i would want a indirect tank added for domestic hot water set up with its zone also would make it the priority zone
    Today I talked to an HVAC guy at my oil company who said the same, though he also wanted to sell me a new boiler to go with it. An indirect tank sounds good - especially if I can hook up the solar water panel someone left here from another project.

    Then I talked to a woman at the front desk who pulled up the amounts of my oil deliveries, and I'm using an average of 60gal/month in the summer just for domestic hot water. (For four adults, washing clothes in cold water!) Winter use is 75-85gal/month. So getting that straightened out is a high priority.


    A good radiant guy would know how to use your current boiler for radiant. Use the Locator map link in my sig and see if any of us are in your area.
    I'd love to find a good radiant guy! No luck so far, and not a single contractor on the Locator Map within an hour of me. What I've got to choose from are a few HVAC guys with limited experience with radiant floors who are willing to give it a go.

  5. #5
    Join Date
    May 2012
    Location
    Upper Michigan
    Posts
    3,589
    Radiant is a low temp app, you would have a zone for the existing high temperate loop and the radiant would need a mixing valve to lower the water temp. What I mean is two separate loops.

  6. #6
    Join Date
    Jun 2007
    Location
    Minneapolis, MN
    Posts
    743
    We design and install combination wood, propane, electric and oil boiler systems integrating domestic hot water with backup heat.

    First we find the available fuels and the cost thereof. Then look to the space and domestic hot water loads and finally match up the options with your budget.

    There are indoor and outdoor gasfication boilers on the market and some with electric backup built in. Others require piping and controls to use propane for instance. Still others use a condensing water heater with a sub-system for space heating - one of our specialties.

    Indirect water heaters are nearly perfect for boiler based heating systems featuring more peak output than a tankless and three times the life with virtually no maintenance. Any boiler can drive an indirect.

    Whether you use wood to heat domestic hot water or exclusively for space heating is more matter of lifestyle than economics, though we have a client in Alaska who complained that the Triangle Tube condensing boiler was using a lot of gas in summer just to make domestic hot water and he wished now that we would have designed the system to use the wood boiler for all loads saving the Triangle Tube boiler for backup exclusively. With propane over $5.00/gallon we got is point.

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