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Effective BTU ratings for your burners

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BlendieOfIndie

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Hey everyone, I just took some measurements on the power of my stove, and I did a little reading about BTUs on wikipedia. I wanted to measure the effective BTUs of my kettle & kitchen stove top. Let me know if my calculations are off. Has anyone else taken these measurements? What were the results & what's your setup?

My setup:
Kitchen stove, 2 burners (kettle straddles the two)
7.5 gallon stainless kettle (14" diam, 12" height); the sides are really thin


Heating up water with kettle lid OFF:
Start temp: 141F
End temp: 168F
Change in temp: 27F
Time: 7 min
Gallons of water: 3
Pounds of water: 25
BTUs: 25 * 27 = 675
BTUs/min = 96.4
BTUs/hour = 5785


Heating up water with kettle lid ON:
Start temp: 134F
End temp: 192F
Change in temp: 58
Time: 20 min
Gallons of water: 5
Pounds of water: 41.65
BTUs: 41.65 * 58 = 2415.7
BTUs/min = 120.8
BTUs/hour = 7247
 
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BlendieOfIndie

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There's something I'd like to add -
Many turkey fryers are rated in the range of 50k to 65k BTUs. Am I correct in assuming that this is BTUs/hour? It wouldn't really make sense to me to rate a burner in BTUs as that's a measure of energy; on the contrary, measuring in terms of power (energy per unit time) *would* make sense. That's the basis of my assumption.

Next, a burner that has a specific BTU rating does not deliver the same amount of energy to your water/wort/whatever. The BTU rating on the burner is the theoretical maximum. Therefore it makes sense for brewers to measure the effective BTU rating of their burner - that is how much energy is actually delivered to your liquid. Knowing the effective BTU rating would allow HBT to quantitatively describe a "rolling boil".

Hope this clarifies the objectives of this post.
 

Bobby_M

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Yeah, the burner BTU is how much heat is can put out. The effective BTU, as you're measuring, is how much of that heat is making it into the liquid.
 

Funkenjaeger

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BlendieOfIndie said:
There's something I'd like to add -
Many turkey fryers are rated in the range of 50k to 65k BTUs. Am I correct in assuming that this is BTUs/hour?
Yes, I'm fairly certain it's actually BTU/h.

BlendieOfIndie said:
Knowing the effective BTU rating would allow HBT to quantitatively describe a "rolling boil".
Maybe on an electric stove where you have to leave it on high heat to maintain a boil, but on my propane burner I turn the heat way down after reaching a boil, and maintain a good rolling boil. So, determining the effective BTU/h while heating the water wouldn't tell you anything about the boil.

Not to mention, the BTU/h that it takes to maintain a particular level of rolling boil would depend on a number of factors (ambient temperature, size and shape of the pot, amount of wort being boiled, etc) so one person's measured numbers would not necessarily be all that useful to others.

Personally I think it would be much simpler and easier to just go look at a picture or video of what someone calls a 'rolling boil' if you are really unsure... Though I'm really not sure where the confusion lies as I would think anyone who has (for instance) boiled water to make pasta should be pretty familiar with what a rolling boil looks like.
 
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BlendieOfIndie

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Funkenjaeger said:
Maybe on an electric stove where you have to leave it on high heat to maintain a boil, but on my propane burner I turn the heat way down after reaching a boil, and maintain a good rolling boil. So, determining the effective BTU/h while heating the water wouldn't tell you anything about the boil.
Good point. I didn't consider that some people don't use full blast. For me, having this number can be useful for planning out my brew day - I can calculate how long it takes to bring X amount of water to temperature T. But I'm curious if I'm getting the same amount of heat as "the experienced guys." My boil is questionably rolling. I'm kinda curious if I'm getting enough protein coagulation/dms boil-off/etc (there doesn't seem to be a problem, so maybe I should forget about it).

Funkenjaeger said:
Not to mention, the BTU/h that it takes to maintain a particular level of rolling boil would depend on a number of factors (ambient temperature, size and shape of the pot, amount of wort being boiled, etc) so one person's measured numbers would not necessarily be all that useful to others.
You're right, all of these factors do matter - that's exactly what I want to measure. Is my water receiving the same amount of heat as other people's water. (This might ultimately be used to justify buying a turkey fryer).

Funkenjaeger said:
... I would think anyone who has (for instance) boiled water to make pasta should be pretty familiar with what a rolling boil looks like.
I guess I'm some kind of empirical freak :rockin: .... :eek:


You're making a good point though. I should prolly be asking myself: am I having problem from to weak of a boil? I believe the answer is no. Anyway to tell?
 
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