Non Electric Gas Boiler

Discussion in 'Boiler Forum' started by CharlieK, Jun 24, 2011.

  1. CharlieK

    CharlieK New Member

    Messages:
    1
    Location:
    Philadelphia, PA
    Years ago I had a house with a natural gas steam boiler controlled by a milliivolt thermostat. When the power went out my boiler kept running having no need for electricity. As a builder we have a few clients looking to have their heat not be electric grid dependent. Anything made today that's more modern and effocient than my old unit that might do the same using NG or propane?
  2. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,793
    Location:
    Long Island, NY
    check with your local propane dealer and/or the public utilty that supplies natural gas. That's what I would do.
  3. Dana

    Dana In the trades

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    Location:
    01609
    Old-school high-mass steam or gravity-feed convecting hydronic systems rarely exceed ~60% efficiency, but there's no inherent reason a properly sized lower mass steam boiler with millivolt controls couldn't hit 70-75%. I'm not sure that would meet minimum efficiency & valving safety standards for legal sale in the US though.

    Convecting millivolt wall furnaces exist (probably operating in the ~75% efficiency range), eg:

    http://www.empirecomfort.com/EMPIRECOMFORT/pdf2011/DVWallFurnaces.pdf

    There are probably low-voltage DC versions that could run code-legal valves, but it still wouldn't meet code on minimum efficiency.

    To get higher AFUE efficiency than 78% usually requires some sort of blower or pump to generate sufficient turbulence for more effective heat exchange.

    http://www.empirecomfort.com/EMPIRECOMFORT/pdf2011/HighEfficientDV.pdf
  4. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,226
    Location:
    Maine
    But Dana, he wants to know if he can get a new one and as far as I know the present energy standards won't allow anying with a standing pilot for heating.
  5. Dana

    Dana In the trades

    Messages:
    2,919
    Location:
    01609
    For hydronic boilers 80% AFUE is achievable and legal with standing pilot ignition, but that requires pumps and some power to run the gas valves.

    Min-legal spec on steam is 75% AFUE, (also achievable with standing pilot, without forced-draft burners), but codes don't allow the type of gas valving used on millivolt systems, so it's still grid-dependent on the internal controls, even if it uses next to zero electricity.

    So bottom line, no, with the possible exception of off-grid cabins other situations where millivolt wall furnaces might be permitted, your options for zero grid-power heating systems are nil. Some DC-systems with designed for big RVs and the like might cut it if your heat loads are miniscule, but I don't have a handle on that market.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,825
    Location:
    Cave Creek, Arizona
    The "nonelectric" boilers had to be either steam or gravity hot water, neither of which is very popular these days. A thermopile could operate a gas valve to turn the burner on and off, but that was all.
  7. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,226
    Location:
    Maine
    Besides the advent of more complicated and safer control systems the main reason why you can't do what you want is because millivolt thrermostatically controlled gas valves had a nasty habit of failing in the full on position.
  8. BadgerBoilerMN

    BadgerBoilerMN Master Hot Water Mpls,MN

    Messages:
    303
    Location:
    Minneapolis
    There is little purpose in being "off the grid" if you have to depend on the propane truck.

    Answer; wood-fired out door boiler with DC motor.
  9. tk03

    tk03 New Member

    Messages:
    56
    Location:
    Harrisburg, pa
    As everyone stated above the Milli-volt is no longer available in boilers. You can still buy 24 volt standing pilot boilers. Manufacturers can build them until Sept 1, 2012.

    Badger good point about the LP truck.
  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,825
    Location:
    Cave Creek, Arizona
    quote; There is little purpose in being "off the grid" if you have to depend on the propane truck.

    That is why the propane tank has a gauge on it with the red zone being once it reaches 20%. You should NOT wait until it is empty to call for a refill. If your propane truck cannot get to you with a couple of week's notice, you are buying from the wrong company.
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