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Question:

Hot water boiler sizing?

Im looking to change a heating system from forced air to hot water/baseboard. Im a plumber. I work for a comp., I install boilers but I never had to size a boiler. Im putting in about 140-150' of baseboard in a small 2 story house. I'd love to put in a Williamson 125000btu (or so). Is that too big? The houses old furnace was 110000btu.

Answer:

There are free heating calculators online that are not that hard to use and pretty easy to find if you look. In the heating industry we always in the past sized on the side of caution thinking that more is better and this really is not the case, there are several problems that occur when you oversize a boiler. In the last 3 years i have put caution to the wind and installed what the program has told me to install and I was surprised by the results. The smaller boiler worked and worked well. I just sized a house in Utica NY about 1400 sq feet with new windows and up to code on the insulation and the heat-load calculator came up with 40,000 BTU'S.They don't make a boiler that small so we went with a 60,000. There is a big saving in everything when you properly size a boiler including materials. Who told you you need 150 feet of baseboard I can heat a mini mansion with all that baseboard.You should reconsider your plan. And please if you are going to install all that baseboard do not do it in one loop, break it up into at a minimum of three zones. You know if you called the boiler rep I bet he would calculate the house for you for free. good luck Greg Murphy
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I have an old uninsulated 2 story house of about 1000 square feet.It is oil fired steam with a 100000 BTU boiler that uses about 50000 BTU /hr on a cold day.I live in Massachusetts.There are so many factors to consider,I think that you can not go wrong putting in a boiler that might be too big.Hope this helps.

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