energy efficient boiler?


Old 03-14-06, 12:23 PM
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energy efficient boiler?

We are in process of seeking the best energy efficient boiler. The more we search the more confused we become. Burnham, Buderus, crown etc. Our home is 2800 sq ft. and has 3 zones. None of the sites give info on how to choose the right size boiler. I could go by the size we have now...but who knows if it is the correct size. Any suggestions would be very helpful. Thank you for your time and interest in my problem.

Old 03-14-06, 01:09 PM
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Typically what should be done is a thing called a Manual J heatloss calculation. It takes the dimensions of your house on a room by room basis and factors in things like how air tight the construction is, what type is insulation you have, the types of doors and windows etc. You also say what inside temperature you prefer and factor that against what the design day temperature should be for your area. The design day temperature is basically the lowest temperature you get during the typical year. From this it calculates how much heat your house will lose. You need to buy a boiler that's net heat is equal to the heatloss. The gross heat for the boiler times the efficiency equals the net heat. The heatloss number tends to be a little overstated for hydronic heat but serves as a good guide.

For an existing building you can also do the following reality check. On the coldest day of the year, how many hours does your current boiler operate? If your current boiler has only 8 hours of run time on the coldest day of the year, you know that you can easily use a boiler that has half the capacity.

Outside of sizing, some majors factors are what type of fuel you plan to use or consider, what type of heat emmitters are in place in the house and the temperature of water that they will see on seasonal days, cold days and design days. Then you can consider specific boilers.

Typically, most people should spend their time researching a good heating contractor. They'll do the above for you (they may charge a consult fee - it takes time to do a heatloss calc), then they'll recommend their preference(s) for you particular application. They would pick a boiler that has good representation in your area and that they have typically installed and know well. The boiler is one part of the system and a great boiler set up in a badly designed system will be less efficient than a crappy boiler that is part of a well-designed heating system. Boilers need to be installed according to the manfacturers' specifications for warranty purposes. This is important since it needs to be piped properly (and also things like venting, gas supply piping sizes etc.). Some contractors will just want to swap out your current boiler with a similar sized boiler and be done with out. That's what you don't want.

Good luck...

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