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  • gas boiler capacity

    Thinking about conversion to gas from oil. Plumbers are on the way for evaluation but want to know more from experts here.

    how to determine the capacity of the gas boiler? can we estimate it by total areas plan to heat? we have 1600sqft in main floor but want to heat the full basement as well, so is about 3000sqft. For the Weil-McLain Ultra Series 3, which one is good for our need, UG-105, UG-155, UG230 or ...?

    Somebody says using the baseboard we have to calculate but some of the rooms use electric right now and some of basement rooms have no heating at all right now. And we plan to add them later.

    what will happen if the capacity is bigger than needed? efficiency will drop? Why I ask is we plan to heat 3000sqft, but some times we may only turn on the main floor but not the basement. or some times we only need heat in living rooms but not bedrooms. How to match the plan to actual use cases?

    thanks,

  • #2
    Re: gas boiler capacity

    Slant-Fin has a program to size your heating system available for download on their website. It takes into acount wall construction, ceiling heighsts, glass content etc. should answer all of your questions.

    Comment


    • #3
      Re: gas boiler capacity

      http://www.slantfin.com/index.html Cannot find that software you mentioned. They removed it?

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      • #4
        Re: gas boiler capacity

        I apologize I couldnt find it either. If you give more information I may be able to help you out better. Tell me about your walls, 2x4 or 2x6, r16 insulation? How much glass 3/4 of the walls are windows? How do you plan to heat your water, tankless coil indirect or water heater? how tall are your ceilings, 8' with 2x8 rafters and r-19 insulation? attic, insulated where are you located, altitude how cold are your winters? I know I asked alot but the more information taht you give me ther more that I can give you!

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        • #5
          Re: gas boiler capacity

          Originally posted by wrench spinner View Post
          I apologize I couldnt find it either. If you give more information I may be able to help you out better. Tell me about your walls, 2x4 or 2x6, r16 insulation? How much glass 3/4 of the walls are windows? How do you plan to heat your water, tankless coil indirect or water heater? how tall are your ceilings, 8' with 2x8 rafters and r-19 insulation? attic, insulated where are you located, altitude how cold are your winters? I know I asked alot but the more information taht you give me ther more that I can give you!
          thank you Sir.

          We bought the house from bank and no info from previous owner about the house. The house was built in 1950 and has an addition in 1980's, I think. It is one floor ranch in Boston MA, very cold in winter.

          Don't know the wall size and its insulation. Many windows, four of them are bigger (in living room and family room), yes, almost 3/4 are windows.

          Hot water tank is heated by solar panel plus electric and we will keep that.

          Ceiling is about 7'8". Attic insulation is good and I added more this year.

          Basement is full basement and all are underground, not a walkout one.

          Thanks,

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          • #6
            Re: gas boiler capacity

            How's your math?

            Download the PDF version of the Burnham heating helper
            http://www.burnham.com/PDF/htghelper.pdf

            Chapter 6 has a heat loss calculator

            As for the boiler...the Weil Mclain Ultra boiler is a self modulating condensing boiler. It will adjust the firing rate based on heating requirements unlike most conventional boilers that have 2 speeds...all the way on, or all the way off. Oversizing is not so much of an issue. Just based on the numbers you have given I'd say a 105,000 but let the installer do a load calc for you.

            Bill

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            • #7
              Re: gas boiler capacity

              based upon what you gave me your heatloss is approximately 100,000 BTU's i figured 2x4 walls, with 3 1/2" insulation 200 sq. ft. of glass, (25 windows, or sliders etc) no heated attic but 6" insulation above ceiling. Based upon my calcs you would need the UG-105 I see no problem with that. You can improve your efficiency with this unit if you make sure that your windows are double pane etc. I figured the worst, anything that you can do to make your house more energy efficient will only help you.

              In conclusion the UG-105 will suit you fine, for example if your windows are double paned, you would only need 92,000 BTu to heat your house, If you put storm windows on and weather strip your doors the BTU goes down even more! Long story short, in the WORST CASE scenario for your house the UG-105 will handle keeping your home comfortable, any further improvements will just help it you do not NEED a bigger boiler based upon what you gave me.

              Now if you plan on an addition in the future I do not feel as though upsizing to the 155 will hurt.

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              • #8
                Re: gas boiler capacity

                PS you may want to contact Duck Butter, he is proffient in this work and does work in your area!

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                • #9
                  Re: gas boiler capacity

                  Originally posted by wrench spinner View Post
                  based upon what you gave me your heatloss is approximately 100,000 BTU's i figured 2x4 walls, with 3 1/2" insulation 200 sq. ft. of glass, (25 windows, or sliders etc) no heated attic but 6" insulation above ceiling. Based upon my calcs you would need the UG-105 I see no problem with that. You can improve your efficiency with this unit if you make sure that your windows are double pane etc. I figured the worst, anything that you can do to make your house more energy efficient will only help you.

                  In conclusion the UG-105 will suit you fine, for example if your windows are double paned, you would only need 92,000 BTu to heat your house, If you put storm windows on and weather strip your doors the BTU goes down even more! Long story short, in the WORST CASE scenario for your house the UG-105 will handle keeping your home comfortable, any further improvements will just help it you do not NEED a bigger boiler based upon what you gave me.

                  Now if you plan on an addition in the future I do not feel as though upsizing to the 155 will hurt.
                  My long-term plan is add another floor on the top. So I take basement into account now and if we have second floor, the basement will not need heating anymore.

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