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Author Topic: Btus  (Read 2282 times)

coolidge

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Btus
« on: December 14, 2014, 12:41:50 PM »
Is there a way to figure how many btus your furnace is actually producing?
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artbaldoni

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Re: Btus
« Reply #1 on: December 14, 2014, 02:38:20 PM »
A Btu is what is required to raise one pound of water 1°. I guess if you know how much water you have and have a way to track temp rise over a period of time you can figure Btus per hour. I think... :o
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Re: Btus
« Reply #2 on: December 15, 2014, 05:41:00 PM »
A lot of variables there. Wood type , moisture  content, water volume and fire box size to name a few.
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Re: Btus
« Reply #3 on: December 15, 2014, 08:23:14 PM »
Quote from: coolidge on December 14, 2014, 12:41:50 PM
Is there a way to figure how many btus your furnace is actually producing?

Assuming that you're talking about your furnace opposed to your boiler, there's two things you need to know to determine the btu rating:  temperature change (delta t) and flow rate of air (cfm).  By looking at the specific heat capacity of air at these two temperatures and knowing the delta t, you can calculate the btu output.

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Re: Btus
« Reply #4 on: December 15, 2014, 11:59:31 PM »
 :post:
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userdk

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Re: Btus
« Reply #5 on: December 16, 2014, 12:13:26 PM »
In a roundabout way, you could figure the btu's used by your house, domestic water, and heat loss on your line, thus coming up with the total.
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jreimer

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Re: Btus
« Reply #6 on: December 17, 2014, 09:38:49 AM »
The easiest way that I have measured the output of my furnace is by timing how long it took to raise the water temperature a set amount, (say from 140 to 180) leaving a circulator running to ensure all the water in the furnace gets heated equally.  Do not put a heat load on your stove while doing this. 

Knowing the volume of water in your stove lets you easily calculate the btu output.  I have calculated this value in multiple ways such as mass of wood burned, efficiency rating of the stove etc. and the numbers all seem to match each other fairly closely so I am confident in my results.
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Re: Btus
« Reply #7 on: December 17, 2014, 11:51:03 AM »
Quote from: userdk on December 16, 2014, 12:13:26 PM
In a roundabout way, you could figure the btu's used by your house, domestic water, and heat loss on your line, thus coming up with the total.

Easiest and most accurate way would be a heat loss calculation on the buildings ur heating. You would adjust the temps in the calculator for indoor and outdoor temps over the time period your testing. Close monitoring of these temps will give you a number with the lowest error rate.

HLC programs have built in fudge factors, how much depends on which one you use. I recommend using John Siegenthalers , as they are very accurate. But not necessary to spend.  Using other math / wood & water/ time etc, formulas just have more likely for higher error. Good luck
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