What is boiling?

I thought this was better up here then in the DIY where I hang out. The question is,

What constitutes a good boil?

I am wondering this due to another thread about BTUs. I am having a difficult time with the BTUs right now. I have learned that an additional 970 BTUs is needed to convert 1 lb of water into 1 lb of steam. With the electric revolution for boiling wort and my lack of knowledge on what an electric boils looks like. I decided to post this up in hopes it could be discussed and have a little clarification. I did a Google search and the first video of an electric boil that came up was this one. I know he has a thread here and also has this video up on here. My question is, is this a good enough boil?



Again, another one.


The interesting thing to me on this is......There is no bubbles. Zero gas formation. There for not getting the extra 970 BTUs needed to convert the water/wort into steam. What is being seen is just the lost heat due to evap and not a change in state due to heat input. If this is to be considered a good enough boil, then the gas folks can turn things down a bit and save some coin.

See the difference in a gas fired boil?

I am interested in the begging of the video.

in my opinion both are considered rolling boils. Gas formation is important for all beers but more important for others such as beers based in pislner malts due to DMS precursors found in the malt. Just because you can't see a ton of steam in the video doesnt mean its not there plus the second camera is at an odd angle.

My preboil for a 60 minute boil is almost 7 gallons and i boil down to 5.5 with plenty of steam and boiloff. If your boiling off less than a gallon i would say its not a strong enough boil based on my system and having never had issues with DMS or clarity

scinerd3000 said:

in my opinion both are considered rolling boils. Gas formation is important for all beers but more important for others such as beers based in pislner malts due to DMS precursors found in the malt. Just because you can't see a ton of steam in the video doesnt mean its not there plus the second camera is at an odd angle.

My preboil for a 60 minute boil is almost 7 gallons and i boil down to 5.5 with plenty of steam and boiloff. If your boiling off less than a gallon i would say its not a strong enough boil based on my system and having never had issues with DMS or clarity

Click to expand...

Thank you for chimming in.

That's what I am asking. Is the formation of the gas bubbles needed, or is it just a waste of energy?

If there is no need for the extra input to turn the water/wort into a gas, then I would bet the folks running gas as a heat source could see a big savings. If a simple upward pushing of the liquid is all that is needed then....

you need to have a decent amount of boiloff. You will DEFFINITLY know if you dont boil enough because you will get a slight rotten egg odor or taste to the beer from not boiling off the DMS. Its very distinguashable and if that happens just crank up the boil to increase the amound lost over an hour. Boil pilsner malt based beers for 90 minutes and you should be good. That first video looks great- im drooling

scinerd3000 said:

you need to have a decent amount of boiloff. You will DEFFINITLY know if you dont boil enough because you will get a slight rotten egg odor or taste to the beer from not boiling off the DMS. Its very distinguashable and if that happens just crank up the boil to increase the amound lost over an hour. Boil pilsner malt based beers for 90 minutes and you should be good. That first video looks great- im drooling

Click to expand...

I am not having an issue with my beer.

I am asking about energy usage and consumption. System efficiency. Electric boiling may happen fast but, I am wondering if the boil can be compared to a gas boil. An electric boil from what I have seen lacks the punch that is delivered by a burner. Maybe that extra punch isn't needed. If that extra punch isn't needed, then I would bet the direct fire folks could turn down the fire and save some money in gas usage.

Just going by the evap rate, there are several factors that come into play. Just like when one is looking at burner efficiency. I don't "think" that can be used as a comparison. Evap is evap, it will just about equal 8,000 BTUs/hr per gallon, coming from any source of heat.

ahh i misunderstood.....according to this electric required more total energy and is more expensive. It goes on to break everything down by BTU's etc

http://www.associatedcontent.com/article/100280/which_is_better_gas_or_electric_heat.html

Here's my electric boil. Considerably more vigorous than the examples previously posted.

JKarp is a good example...

I have found that in 8 gallons, when I am running 3700 BTUs that I get 1.3 gallons/hour boil off. If I want more, I increase the power output by cycle time, if I want less, I use less power. I am actually REALLY surprised to see that 7000W boil being so tame... my old kettle was much more vigorous looking than that. My new kettle is 2x the wattage of my first...

I use 9000W (30k BTU) to reach the boil, and then drop it to 3700W (12.6K BTU) to maintain a 1.3 gallon/hr boil off.

As for the "punch" of gas... I dont see where the punch comes in when electric is actually heating faster. It takes less time to reach a boil, and it only takes 3.7kW to boil off 1.3 gallons/hour... that is not much power at all, and most people are pimping BKs that are 5500-9000 watts.

How is electric more expensive? There have been threads here on HBT detailing the cost to use electric and it amounted to less than $2 to run the elements, pumps, everything, for a full brew session. (HLT, Pumps, BK)

Even if I ran my 9000W kettle at full blast (which would be a BAD idea) for 90 minutes to boil...

That is 13.5 kWh

I pay about $.1 per kWh (the national average is about $.14 or so)

That is $1.35... BUT I dont do that, 9000W is WAYYY too much.

I run 9kW for about 10 minutes
Then I run 4kW for 80 minutes

Totaling: 6.83kW

That is $.68 for a 90 minute boil with electric.

Where is all of this information coming from? That electric has less "punch" and that it is more expensive? Have you guys been using both?

scientist3000 said:

ahh i misunderstood.....according to this electric required more total energy and is more expensive. It goes on to break everything down by BTU's etc

http://www.associatedcontent.com/article/100280/which_is_better_gas_or_electric_heat.html

Click to expand...

Heating a home, and heating a kettle are two different beasts...

Electric boils are MUCH less costly than gas fired ones. It is simple math.

Gas is horrilby iniefecient in the delivery of energy to the pot and subsequently the wort. Electric is much more efficient particularly with the sticks actually in the liquid. If gas were more efficient it would be cheaper n many locations.
As far as the steam you cannot see: you cannot see steam.

A theory on bubbles....

With a gas burner you are heating the bottom of the kettle to a temp. that is greater than boiling...

This means that you have that whole surface area where you are creating bubbles, vapor....

With electric you are NOT heating the kettle at all, you are heating the medium, to boiling, not past boiling.

I would think you would see fewer "bubbles" as you dont have the surface area to create them that you do with gas. This is purely my conjecture, but there may be something to it.

As far as the boil, and boil off though, electric does the same things to the beer, it is all boiling.

Fossil fuels contain a great amount of energy, and if you COULD get them to your kettle, you would really have something.

The sun for example, has A LOT of heat potential, but due to the dynamics of the situation, you cannot get that potential into your kettle very efficiently, the same thing is affecting gas burners. They have a HUGE potential, you just arent getting that potential into the wort effectively.

This is why your garage is 90+ degrees in the dead of winter when you are boiling with gas, but 45 degrees when you are boiling with electric. With gas you are heating the planet, or your home... with electric you are only heating the wort.

How many BTUs does it take to heat a 20 x 20 x 9 foot cube from 45F to 95F? That is what a propane burner is wasting while it is heating my wort with gas.

That is 3600 cu.ft of air.

It takes .018 BTUs to heat ONE cubic foot ONE degree...

3600 cuft multiplied by 50F multiplied by .018 BTUs is...

3,240 BTUs

This is not taking into consideration the garage door being open to a degree for ventilation etc... or regular heat loss...

willynilly said:

A theory on bubbles....

With a gas burner you are heating the bottom of the kettle to a temp. that is greater than boiling...

This means that you have that whole surface area where you are creating bubbles, vapor....

With electric you are NOT heating the kettle at all, you are heating the medium, to boiling, not past boiling.

I would think you would see fewer "bubbles" as you dont have the surface area to create them that you do with gas. This is purely my conjecture, but there may be something to it.

As far as the boil, and boil off though, electric does the same things to the beer, it is all boiling.

Click to expand...

Yes, there it is. The whole reason this thread was placed. Gas is placing more heat energy into the liquid there by having a phase change from a liquid right to a gas state. Nothing to do with surface area. A gas burner should be able to be turned down to the point where the bottom of the kettle is acting like an electric element. If a simple rolling of the liquid at 212* is all that is needed, then the gas folks should be able too turn down the heat and save money on gas usage. Maybe I am thinking too much along the lines of a perpetual motion machine, but you get my drift. With out the extra BTU input the phase change doesn't happen.

willynilly said:

Fossil fuels contain a great amount of energy, and if you COULD get them to your kettle, you would really have something.

The sun for example, has A LOT of heat potential, but due to the dynamics of the situation, you cannot get that potential into your kettle very efficiently, the same thing is affecting gas burners. They have a HUGE potential, you just arent getting that potential into the wort effectively.

This is why your garage is 90+ degrees in the dead of winter when you are boiling with gas, but 45 degrees when you are boiling with electric. With gas you are heating the planet, or your home... with electric you are only heating the wort.

How many BTUs does it take to heat a 20 x 20 x 9 foot cube from 45F to 95F? That is what a propane burner is wasting while it is heating my wort with gas.

That is 3600 cu.ft of air.

It takes .018 BTUs to heat ONE cubic foot ONE degree...

3600 cuft multiplied by 50F multiplied by .018 BTUs is...

3,240 BTUs

This is not taking into consideration the garage door being open to a degree for ventilation etc... or regular heat loss...

Click to expand...

You also aren't taking into considering the huge cylinder of boiling liquid giving off heat as well. Not to mention the steam condensing back into a liquid state giving back off its energy. Just in the phase change, 1 lb of steam will throw back 970 BTUs. Multiply that by 8.35 (1 gallon of boil off) and you get a heat transfer of 8099.5 BTUs.

I dont know that it is placing MORE heat (BTUs) in there....

I say this because isnt boil off related to BTUs? Isnt heating time related to BTUs applied?

So if it is, why can a 4,000W element boil off the same as a MUCH larger gas burner? If in fact the gas burner is applying more heat to the wort, why isnt it boiling off more? This theory is all well and good if you are telling me that the gas burner boilers are boiling off say 2x as much, but they arent.

A 4000W element will boil off as much as any gas burner is doing during a regular boil.

This tells me that the BTU input is the same, 4000W is putting as many BTUs in as a gas burner that is running at... whatever it is running it. I boil off the same with electric, as I do with gas, telling me that the BTUs going to the wort, are equal.

GreenMonti said:

You also aren't taking into considering the huge cylinder of boiling liquid giving off heat as well. Not to mention the steam condensing back into a liquid state giving back off its energy. Just in the phase change, 1 lb of steam will throw back 970 BTUs. Multiply that by 8.35 (1 gallon of boil off) and you get a heat transfer of 8099.5 BTUs.

Click to expand...

I am taking that into consideration, but you have that whether you are using electric or gas... that should be equal. So it is not even a part of the equation.

northernlad said:

Gas is horrilby iniefecient in the delivery of energy to the pot and subsequently the wort. Electric is much more efficient particularly with the sticks actually in the liquid. If gas were more efficient it would be cheaper n many locations.
As far as the steam you cannot see: you cannot see steam.

Click to expand...

Unless I am mistaken, You cannot see superheated steam until it cools. There is a visual of water vapor condensing.

willynilly said:

I dont know that it is placing MORE heat (BTUs) in there....

I say this because isnt boil off related to BTUs?

So if it is, why can a 4,000W element boil off the same as a MUCH larger gas burner? If in fact the gas burner is applying more heat to the wort, why isnt it boiling off more?

A 4000W element will boil off as much as any gas burner is doing during a regular boil.

This tells me that the BTU input is the same, 4000W is putting as many BTUs in as a gas burner that is running at... whatever it is running it. I boil off the same with electric, as I do with gas, telling me that the BTUs going to the wort, are equal.

Click to expand...

Isn't boil off governed by surface area of the kettle being used? Amongst other things.
A 4,000W heating element is only delivering 13,648 BTU/hr. Even at a 50% loss to the direct fire method, a 170,000 BTU/hr burner will still get 85,000 BTUs/hr into the liquid.

willynilly said:

I am taking that into consideration, but you have that whether you are using electric or gas... that should be equal. So it is not even a part of the equation.

Click to expand...

I am sorry bro I gotta go and do some plumbing work for a friend. I'll be back later.


Please folks don't be shy, This is great so far. Please chime in.

Okay, who cares if you can see vapor...

What we can see is the boil off.

If you are boiling off equal amounts of water with electric and gas, how can anyone claim that gas is putting more BTUs into the wort? That is impossible, otherwise the boil off would be different.

How can you claim that gas is applying more BTUs to the wort when electric is reaching a boil faster? Again, wouldn't the fact that the heating time is faster then prove that there are more BTUs being applied to the wort by electric?

GreenMonti said:

Isn't boil off governed by surface area of the kettle being used? Amongst other things.
A 4,000W heating element is only delivering 13,648 BTU/hr. Even at a 50% loss to the direct fire method, a 170,000 BTU/hr burner will still get 85,000 BTUs/hr into the liquid.

Click to expand...

We are talking about the same kettle, different heating sources, so again you can throw out the geometry variables. BUT, if you want to include them, that is fine... but surface area affects boil off very little. This is in part because of what you posted GM, 970BTUs per pound water to get the phase change... it will change phases if you have those BTUs in there, regardless of the surface area of the medium you are heating.

I know that a 4000W heating element is only 13.6K BTUs, that is what makes the efficiency of gas burners to sad. I know that 20% sounds REALLY bad, but this has been proven on more than a few gas fired rigs here. The real world number are what matter and although it sounds impossible, they are true numbers posted by brewers.

That 4000W element will reach a boil faster than a 55K BTU burner. People have been testing this for a while, and the HIGHEST eff. I have seen anyone post from their gas burner is 30%... the average is about 23%.

If you have a gas burner, then test it for us. Get a precise amount of water in your kettle, take the start temp and end temp and the time. We can then compare that BTU calculation to the rated BTUs of your gas burner.

What I know is this... boil off and heating time is related to the BTUs applied. If your kettle and volume are the SAME, then you can throw out all of the other variables.

This being said... in my gas keggle I was boiling off 1.3 gallons/hour with a vigorous boil. In my electric kettle I am boiling off 1.3 gallons/hour with 3700W (dialed down from 9000W) So, we can easily assume that the BTU application to the wort is the same, otherwise there would be a discrepancy in the boil off rate. You said it yourself GreenMonti, when you posted the BTUs required to vaporize water.

Also, the 9000W BK (30k BTUs) is reaching a boil in 13 gallons from 160F in 11 minutes... how fast is a much larger gas burner doing this? 30K BTUs isnt much, not much at all, but I can tell you that is a huge volume to heat in 11 minutes! If you had a 60K BTU gas burner, youd be waiting a very long time, I can tell you how long... about 40 minutes according to my watch.

Rated BTUs mean nothing when talking about gas burners, the ACTUAL BTUs that are doing the work, are much much less. The only way to know what you are getting into your kettle, is to do the math. Weight in pounds water, start temp, end temp and the elapsed time.

BTUs applied is easy to calculate, there is no need to speculate. Heating time and boil off are mainly products of the BTUs applied. So, what is the boil off, what is the heating time? The faster the heating time, the more BTUs you are applying, the greater the boil off, the greater the BTUs you are applying.

10F rise per minute in 5 gallons of strike water with (9000W) 30K BTU is pretty impressive, but you cant get that with a 60K BTU burner, you can get about half that (which is about 25% eff)

If you are heating faster, you are applying more BTUs.

If you are boiling off the SAME, you are applying the SAME BTUs.

If you are heating slower, you are applying fewer BTUs.

If you are boiling off LESS, you are applying LESS BTUs.

This is where the whole "gas applies more BTUs to the wort" argument doesn't make any sense to me. It isn't faster, and it isn't boiling off more, so how can it be applying more BTUs? And, if it is slower and not boiling off more, what would you use to justify the statement that it IS applying more BTUs?

GreenMonti said:

Isn't boil off governed by surface area of the kettle being used? Amongst other things.
A 4,000W heating element is only delivering 13,648 BTU/hr. Even at a 50% loss to the direct fire method, a 170,000 BTU/hr burner will still get 85,000 BTUs/hr into the liquid.

Click to expand...

Lets assume you are getting 85,000 BTUs into your kettle (50% eff)... your numbers would look like this.

In 5 gallons, you would be seeing about 50F PER MINUTE rise in temp. Wow.

You would reach a boil, from 160F in 5 gallons in about ONE minute. Wow!

You would reach a boil from 160F in 13 gallons in about 4 minutes. DANG!

As you can see, 50% eff. is HIGHLY unlikely, because people are NOT seeing these heating times. If you DOUBLE the above mentioned heating times, you are now down to 25% eff on that burner.

So if you assume 25% eff. then you can start talking gas usage.

If I use 4kW to boil for an hour (which I do), then that is 13648 BTUs, 4kW for an hour will cost me about $.68 (this takes into consideration 10 minutes to REACH the boil at a higher wattage) It takes about 5000 BTUs to reach that boil... so I am using a total of 18600 (ish) BTUs per boil.

When I boiled with gas, I would get about 5 boils from a tank of LP. That is about 17.5 pounds of propane, each pound containing about 22K BTUs. The full tank contains about 385,000 BTUs, divided by 5 brews, that is about 77,000 BTUs per boil.

Compare the BTU useage that I have between my electric kettle per session (77,000) and my propane burner per session (18,600) and you can see that my burner is 24% eff compared to my electric kettle. Typicaly the HIGHER the BTU rating of the burner, the less eff. it is. The kicker is that my electric kettle is over 2x as fast to reach the boil, and then boils off the same amount as my gas burner.

As you can see, the BTU usage is much different between electric and gas, which is directly affected by the eff. of each type of heat. Gas would cost about $3.20 per session whereas electric was about $.68 per session (for boil only) It is only a couple bucks, so who really cares, but this proves that electric is more eff. and less costly.

Help me with the math here, if you have 13 gallons at 8.4Lb/gallon and need to add 970 btu's/Lb for all the liquid to reach a boil, how long is it going to take with 9 Kw. What might seem like a boil is related to the high surface temperature of the elements flashing the surrounding water to steam but it seems that there is not enough total energy in the kettle to reach a true boil. The water heating to boil temperature is only 15% of the energy needed to boil, the other 85% is the heat added before boil happens.

kladue said:

Help me with the math here, if you have 13 gallons at 8.4Lb/gallon and need to add 970 btu's/Lb for all the liquid to reach a boil, how long is it going to take with 9 Kw. What might seem like a boil is related to the high surface temperature of the elements flashing the surrounding water to steam but it seems that there is not enough total energy in the kettle to reach a true boil. The water heating to boil temperature is only 15% of the energy needed to boil, the other 85% is the heat added before boil happens.

Click to expand...

In your example, almost no one would be reaching a boil, as you would need over 100K BTUs to boil 13 gallons That doesn't even sound right, does it?

To correct this, it takes 970 BTUs to create a POUND of vapor. So if you are boiling off 1.3 gallons of water over an hour you are looking at 10.84 pounds over an hour. That is 10,500 BTUs over an hour. Or are you planning to boil off all 13 gallons in that hour? It doesn't take many BTUs to boil off water as you can see. 4000W (13648 BTUs) is PLENTY of power to accomplish this.

My water boils at 209F, and it takes 11 minutes to get there from 160F. Then I turn it down to 4000W and I get a 1.3 gallon per hour boil off, how much are you boiling off?

I see no difference at all in the boil off rate between my electric kettle and gas, which tells me that the BTUs being applied are the same, I mean, it would have to be, right? Only difference is I am not waiting to get to a boil like I am with my gas kettle.

There are plenty of threads here that cover this, and put it to rest... here is one of them.
https://www.homebrewtalk.com/f11/effective-btu-you-might-surprised-159043/

100K BTU burner actually putting 12K BTUs into the boiler? Yes, that is common.

Gas is really not eff., it isnt applying any more BTUs, otherwise it would heat faster than electric, but it doesn't. So if a heating element isn't "boiling" the wort, then a gas burner certainly isnt either.

GreenMonti's efforts with the boiler and calendria were a way that we could measure the heat delivered to a known quantity of water by the steam generation/condensation heat transfer. With the ability to turn 4.2 Lbs/Min to steam in the boiler and then back to water in the kettle we were able to quantify the heatflow and record the times and temperatures. As the numbers were calculated, the formulas were found to match actual results for heat transfer based on water flow into boiler and its conversion to steam.
All said and done what ever method makes beer is all that matters in the long run, this should not end up a electric Vs.gas debate as they are entirely different methods.
My efforts to date have been direct injection of steam for wort heating/step mashing, and soon to follow with GreenMonti's help, steam wort boiling.
When revised boiler coils and calandria are installed in new system the data logging in the control software will help resolve the questions about amount of heat needed to boil.

I dont care what method people use to heat their systems either. But it does no good to have a plethora of false information out there, that doesn't benefit the community.

Bottom line, you need about 10,500 BTUs to boil off what most HBers boil off in an hour. According to testing completed by myself and others, gas burners under a kettle are 20-30% eff. and therefore typically heat slower than electric kettles, it is just a matter of BTUs and volume.

This thread started off as a gas boil vs electric boil thread... that is why it is where it is.

Both work well, I have used both extensively, but to say that electric kettles are slow, more costly to operate (energy), or that they do not truely "boil" the wort, are all false.

Whether you have a 4000W heating element or a 60K BTU burner, you are doing the exact same thing, same times, same boil off... one is just louder and more expensive to operate than the other during that hour.

GreenMonti said:

I thought this was better up here then in the DIY where I hang out. The question is,

What constitutes a good boil?

I am wondering this due to another thread about BTUs. I am having a difficult time with the BTUs right now. I have learned that an additional 970 BTUs is needed to convert 1 lb of water into 1 lb of steam. With the electric revolution for boiling wort and my lack of knowledge on what an electric boils looks like. I decided to post this up in hopes it could be discussed and have a little clarification. I did a Google search and the first video of an electric boil that came up was this one. I know he has a thread here and also has this video up on here. My question is, is this a good enough boil?

http://www.youtube.com/watch?v=KEt1fDhWN6s

Again, another one.
http://www.youtube.com/watch?v=LPAUlLdHAt4&feature=youtube_gdata

The interesting thing to me on this is......There is no bubbles. Zero gas formation. There for not getting the extra 970 BTUs needed to convert the water/wort into steam. What is being seen is just the lost heat due to evap and not a change in state due to heat input. If this is to be considered a good enough boil, then the gas folks can turn things down a bit and save some coin.

Click to expand...

So it takes 10,500 BTUs to boil off about 1.3 gallons of water in an hour...

That 7000 BTU kettle is over 21,000 BTUs directly applied to the water...

Why would you go assuming that it is not powerful enough to facilitate the state change? Seems to me that it is overpowered by 100%

kladue said:

Help me with the math here, if you have 13 gallons at 8.4Lb/gallon and need to add 970 btu's/Lb for all the liquid to reach a boil, how long is it going to take with 9 Kw. What might seem like a boil is related to the high surface temperature of the elements flashing the surrounding water to steam but it seems that there is not enough total energy in the kettle to reach a true boil. The water heating to boil temperature is only 15% of the energy needed to boil, the other 85% is the heat added before boil happens.

Click to expand...

Assuming the contents are at 212, for each 970 BTU you will get one pound of water to convert to steam.

A 9000W element is equivelent to 30600 BTU/hr.

(30600 BTU/hr) / (970 BTU/lb.) = 31.5 pounds of water vaporized in 1 hour. That is 3.78 gallons.

BTW, "flashing the surrounding water to steam" would be boiling. Don't fool yourself that entire contents of a pot over a flame is boiling: it is only the bottom inside surface of the pot that is boiling.

passedpawn said:

Assuming the contents are at 212, for each 970 BTU you will get one pound of water to convert to steam.

A 9000W element is equivelent to 30600 BTU/hr.

(30600 BTU/hr) / (970 BTU/lb.) = 31.5 pounds of water vaporized in 1 hour. That is 3.78 gallons.

BTW, "flashing the surrounding water to steam" would be boiling. Don't fool yourself that entire contents of a pot over a flame is boiling: it is only the bottom inside surface of the pot that is boiling.

Click to expand...

Right PP....

9000W will boil off about 3.5 gallons per hour, which is why it gets reduced to 4000W, which is just above what I need for 1.3 gallon/hr boil off.

9000W is only 30K BTUs, but that is A LOT of heating power when you are getting 100% applied to the wort!

If you had a 30K BTU gas burner, youd be sitting there all day.

There is a misconception here that when water in a pot boils, it ALL boils. No. Only the water leaving as steam has boiled. The rest haven't received their 970 BTU's/lb. of energy, and are sitting calmly hoping to get to the bottom of the pot where the heat is entering.

I don't understand why this thread is going downhill with all of these arguments about what constitutes a boil. Most of the arguing is adding no value whatsoever.

Back on topic, my 5500W electric kettle is capable of vigorously boiling 18 gallons of wort (after a bit of a wait, of course), but I usually dial it back to maintain a boil that looks very similar to the first video. I'm quite satisfied with the results, and I've yet to taste any DMS.

passedpawn and willynilly are correct.

In a brewing situation, it would generally be much cheaper to go electric. Traditional gas fired is terribly inefficient. maybe if you run a water heater type design, or maybe monti's boiler design gas can approach electrics costs. Gas furnaces are generally cheaper to operate because the price of gas is low and the temperature of the air being heated is also relatively low and its running at a comparatively high mass flow rate for good heat transfer. Theres really quite a bit more to add, but I don't feel its worth the time.

1 BTU to get 1lb of water to rise in temp 1F

13 gallons water is
108 pounds of water

From 60F to 210F:
16,200 BTUs required to heat in an hour
If you have 32.4K BTUs it will take you 30 minutes to accomplish this.

970 BTUs per POUND to create water vapor.
Creating 1.5 gallons of vapor per hour (boil off)
12.5 POUNDS of vapor per hour
12.5 x 970 BTUs per POUND per hour
12,125 BTUs to create 1.5 gallons of boil off per hour

1kW equals 3412 BTUs
12,125 BTUs equals 3.5kW
3.5kW equals 3500W

3.5kWh at $.12 per kWh
$.42 to boil off 1.5 gallons in one hour (unless you are in Hawaii)

After review of the boiler and calandria test runs with flash boiler @3.1 Lb/Min steam output, and only condensed steam leaving kettle, a theoretical transfer of 3055 Btu's/minute was calculated. With continous heat input to 12 gallons for 15 minutes to raise the water temperature from 50 - 160 degrees, an effective heat transfer rate was calculated at 1088 Btu's/Minute. Continued heat application at the same heating rate brought container to a boil with an additional 30 minutes of heating, with the calculated addition of 32.66K Btu's. While the measurements were less than scientific the boil should have happened much sooner if only an additional 970 Btu,s were needed over water heating to 212. It appears that the heat applied is diffusing into surrounding water and a significant amount has to be dumped into the container to reach a boiling point around the heat source. The amount observed was about 1/3 the expected 970 btu's/lb but still more than just 970Btu's over 212 degree water. During testing live steam was not lost from condensate line so most of the latent heat of the steam should have been going into the water, what was not quantified was the container heat losses through the sides and evaporation.

Wow, I wish I was there.

I am hoping to have a new boiler built by May R&R run home, and install it in the new system so all the flows and temperatures can be recorded. With gas flows, liquid flows, and system temperatures controlled and logged, just need to write calculations to be able to do a realtime heatflow during heating and boiling with both direct fired BK burner and steam heating.

So if I am reading that correctly, which I may not be... it took 45 minutes to go from 50F to a boil in 12 gallons, correct?

If I am reading that correctly, that is 21,496 BTUs, or the equivilent of 6300 watts. (weight, temp. delta, and time)

I am probably reading that wrong.

I dont understand steam, so I apologize if I am missing something. If you are effectively APPLYING 1088 BTUs per MINUTE, that is 48,960 BTUs APPLIED in 45 minutes.

Your heating time of 45 minutes from 50F to a boil doesnt add up if that is the case. 48,960 BTUs in 45 minutes is INCREDIBLE, whereas 50F to a boil in 45 minutes is really quite lengthy.

With 48,960 BTUs effectively APPLIED to water, you could effectively BOIL 27 gallons of water in 45 minutes. Not 12. You only have to apply 355 BTUs per minute to reach 16,013 BTUs which is what it takes to get from 50F to 210F.

Phase change aside, is the 355 BTUs per minute correct to get from 50F to 210F in 45 minutes?

willynilly said:

Also, the 9000W BK (30k BTUs) is reaching a boil in 13 gallons from 160F in 11 minutes... how fast is a much larger gas burner doing this? 30K BTUs isnt much, not much at all, but I can tell you that is a huge volume to heat in 11 minutes! If you had a 60K BTU gas burner, youd be waiting a very long time, I can tell you how long... about 40 minutes according to my watch.

Click to expand...

Are you turning on the element while it is filling? Once its covered.