# BTURating

• posted on March 5, 2006, 9:45 pm
Hi, Iam looking at putting a large extension on my house. 2 rooms ground and upper floor. Does anyone know how I work out if my exsisting boiler will be man enough to heat the additional rooms. I know I have to find out the overall BTU calculation but how is this done. Help would be much appreciated.
Dave
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• posted on March 5, 2006, 9:55 pm

Call a pro in your area and have them do a manual J calculation for the house then for the addition.
Some boilers were oversized in the old days, but time and age reduce the amount of heat produced.
Chances are you looking at a complete new system. Considering the addition. The air movement in the old space will be completely different than the new.
Your boiler should state how big it is, then back to the first statement.
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• posted on March 5, 2006, 9:58 pm
snipped-for-privacy@ntlworld.com wrote:

You need to do a manual calculation and it involves some work.
The Department of Energy's information on heating and cooling sizing.
http://www.eere.energy.gov/consumer/your_home/space_heating_cooling/index.cfm/mytopic340
--
Joseph Meehan

Dia duit
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• posted on March 6, 2006, 1:39 am
Dave,
If you add enough insulation, it will reduce the likelyhood that you will need a new boiler. Get the guy who will be doing the heat piping for the room addition to do the Manual J load calculation.
Stretch
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• posted on March 6, 2006, 5:04 pm
general ideas: where? [location affects climate demands.] age of boiler? present size of boiler btu? here's some dumb ideas: on the coldest day of the winter with the wind chill at its coldest, does the boiler water satisfy the house zones thermostats now? what water temperature does it peak at to do that now? depending on the system's present adjusted limits, what does the boiler's instruction manual allow for maximum temperature? is there much room left to the maximum range? also on our boiler system if the house gets completely cold from an unreported malfunction, it takes 6 to 8 hours to reheat the house in winter starting with a cold boiler. you will run all your separate zone valves and zone thermostats for each room for efficiency. otherwise, if you install central air you may be considering a separate forced air hvac system for the addition.
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• posted on March 6, 2006, 6:48 pm
On 5 Mar 2006 13:45:56 -0800, snipped-for-privacy@ntlworld.com wrote:

If you're willing to settle for a rough approximation, then you measure all the outside surfaces of the projected house, (So many square feet of wall, so many square feet of window, so many square feet of door, so many square feet of ceiling, so many square feet of floor)
Then you find the R values of each of those areas, invert to get the U value, and multiply by the square feet for each. Separate out the value for the floor. Add all the other "U"s together and call the result X.
Subtract the temperature you want the house to be at from the temperature of the coldest day you expect to ever see. Multiply the result by Y, and call the result Z.
Multiply the "U" for the floor area by the average temperture for your area, or 45 if you don't know what the average is. Add the result to Z. That's the BTU output you'll need for your furnace.
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• posted on March 6, 2006, 11:34 pm
BTU/H
A BTU is a lump of heat...meaningless by itself. It's the rate BTU's per Hour that matters.
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