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I am researching installation of a gas boiler for heating and indirect DHW.

David_L12David_L12 Posts: 4Member
I was initially researching the installation of a condensing Combi unit (Lockinvar Noble) to provide DHW and heat for my radiant flooring, but after talking to a couple of local HVAC techs they advised against it. There concern was with my Nat gas supply, my gas is Raw Natural Gas from oil wells on the property. They are not sure if the Raw Nat Gas will cause problems with all of the sensors and valves used in the modulating systems in the new combi units so they recommended installing an old style non-modulating cast iron boiler.

This is a new relatively tight house without a chimney so I have been looking for boilers with power vent and exterior makeup supply (preferably sealed combustion) but am not finding many options available.

- Does anyone have experience with Raw Natural gas use in modern modulating boilers?
- Can anyone recommend a reliable boiler meeting my requirements?
- Two boilers that have been mentioned are the Dunkirk XEB Series 2 and the U.S. Boiler ESC, can anyone provide comments on either of these boilers?

Any comments or recommendations are appreciated.

Thanks, David

Comments

  • DZoroDZoro Posts: 902Member
    Hmm, I'd be concerned with any gas valve if that is truly a issue with your gas supply...
  • ZmanZman Posts: 5,262Member
    I would not run any boiler without some assurance that the gas is clean enough. All boilers have similar gas valves and orifices that can become clogged. I better question might be "what filters and sediment catches should I use to assure clean gas to my appliances?"
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • HomerJSmithHomerJSmith Posts: 627Member
    edited October 23
    As you already know, raw N/gas is really dirty, in most cases, and you don't know the BTU's in a cubic foot of gas which can vary considerably.

    Find out the quality of your raw gas before a final decision.

    I would probably rethink this and maybe not go with a high efficiency modulating boiler despite the savings. Perhaps, a conventional high or medium mass boiler with an indirect tank would be a better choice.

    What are you heating your house with now?
  • David_L12David_L12 Posts: 4Member
    DZoro and Zman,

    The gas is filtered through a water/sediment separator, their concern is based on the other gases (butane, etc) within the Raw N/Gas and how or if the modulating system would react to them.
  • David_L12David_L12 Posts: 4Member
    HomerJSmith,

    I will probably have the gas tested just for curiosity but I have been using it for our cooktop for 3 years with no issues and several people in the neighborhood use it in conventional boilers with no problems.

    Your recommendation for a conventional boiler and indirect tank follows their recommendations and is probably the route I will take.

    I currently heat/cool my home with a (5 ton) ground loop geo unit, which works fine, but with the recent availability of cheap (free) gas my plan is to use a gas boiler to heat the radiant batch tank during the winter and replace my electric DHW heater with an indirect setup. Using prices for a mid grade boiler vs electric the boiler should pay for itself in approx. 7 years.

    Do you have any recommendations for reliable conventional boilers?

    Thank You,
    David
  • DZoroDZoro Posts: 902Member
    Sounds like your local recommendations will be your best bet. :)
  • JUGHNEJUGHNE Posts: 6,074Member
    Is copper tubing used for piping this raw NG?
  • David_L12David_L12 Posts: 4Member
    Jughne,

    The piping is standard Black pipe.
  • ZmanZman Posts: 5,262Member
    If the makeup or the natural gas is unusual, it should work fine in a mod/con once the combustion is dialed in. If the makeup and btu content is variable, the mod/con won't like that at all.
    Conventional cast iron boilers are all pretty similar in design. I would base the decision of local support.
    You will probably want to use a smart mixing valve like the taco I-series to manage the outdoor reset for the radiant and boiler condensate protection.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • HomerJSmithHomerJSmith Posts: 627Member
    edited October 24
    My concern would be gumming up a gas valve. A conventional gas valve is a lot more forgiving than a mod con variable flow gas valve. Just saying.

    Even Propane has some butane in it.
  • mattmia2mattmia2 Posts: 265Member
    Are there any mod/cons with an oxygen sensor like a car that vary the mixture based on the results of combustion?

    the gas valves in both conventional and mod/con boilers rely on the gas having fixed energy content per volume, they regulate volume, not heat output so any gas appliance except something like a cooktop where the heat output is adjusted by the user will over and uder fire if the composition of the gas isn't consistent. This also means a combustion analysis is super important to get the mixture and firing rate right.
  • Jamie HallJamie Hall Posts: 11,204Member
    You mean the little gadgets on the exhaust pipe which light the check engine light? No, so far as I know, no. Reason being they are expensive and finicky and quite unnecessary for a properly adjusted boiler.
    Jamie

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • mattmia2mattmia2 Posts: 265Member
    No. i mean a boiler that uses an oxygen sensor in a feedback loop with the gas valve controls to keep the mixture of the gas that is being burned correct. in a situation where the incoming gas varies in energy content per volume it would seem to be the only way to keep it burning properly.
  • Jamie HallJamie Hall Posts: 11,204Member
    mattmia2 said:

    No. i mean a boiler that uses an oxygen sensor in a feedback loop with the gas valve controls to keep the mixture of the gas that is being burned correct. in a situation where the incoming gas varies in energy content per volume it would seem to be the only way to keep it burning properly.

    I knew, and know, exactly what you meant. My attempt at humour failed. So far as I know, to be clear, no one makes such a control for a boiler. As I noted, the sensors themselves aren't cheap; the controls that implement that simple feedback loop aren't cheap either. Nor, in virtually all applications, would they be necessary -- the gas quality is very uniform to begin with, and the load is constant or, if modulating, varying slowly and predictably. Could it be done? Sure. And from an engineering standpoint, very simple. From a sales standpoint, no sale -- people are price conscious. From a maintenance standpoint? People don't maintain their boilers anyway -- they certainly aren't going to worry about that.
    Jamie

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
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