How do I calculate the propane I need for a brewing session?

[Elysium]

I am about to buy a 46.5 Kw burner that works with propane gas.
There are two things I’d like to know:
1, I’d like to find out how much gas (propane) I need to get to boiling and boil the liquid for 1 hour.
2, Is 46.5 Kw too much for a 30 gallon batch?

According to an online converter a 46.5kW burner has the potency of 158664.58 BTU.
I have an equation that I got from a user from a previous post which is:
-1 BTU = the amount of energy to heat 1 lb of water 1 degree.
-1 gallon = 8.33 lbs (264 lbs of wort in case of a 31.7 batch)
(this calculation is based on the idea that I am going from room temp to boil)
(212-70)*264=37488
I need 37k BTU (normally people say double that) to reach boil and stay there for 1 hour…so, I need a minimum of 73k BTU, but the burner I wanna buy is 2 times stronger than what I need.

So, is it going to be an overkill?
And how do I calculate the amount of propane I need from room temp to boil and to maintain it at boil temperature for 1 hour?

 

[passedpawn]

Looks like you have all the numbers there to get the answer, except you don't know how much of that energy will "miss" the pot and go off into the air. I'd assume 25% gets into the pot. If so, then in order to get your pot to boil in 1 hour, you'd need a burner that's providing

37k BTU / .25 = 148k BTU / hr

Note that burners are rated in BTU/hr.

Too much capability should be a problem since you can adjust the flame.

Maintaining an adaquate boil will take a lot less.

 

[Dean_Palmer]

You cannot buy too powerful of a burner, but you can't get more heat from a smaller one :-0 Most burners that work well up to 10 gallons are 55k BTU like the basic Bayou Classic, King Kooker, etc. I like the 200k BTU "banjo" models like the KAB from Bayou, or the Blichmann, or the Edelmetal(sp?) (all the same burner element).

As for calculating the amount of gas needed, most people get a few brews off a single 20lb cylinder. Get 2 cylinders and just never worry about doing math, and doing math has nothing to do with running the tank to empty on a brew day when conditions change and you happen to use more. You will have variables and worrying about calculating propane should not have to be part of your brew day.

Also, you don't want to go refill a tank that still has gas in it as I never see places around here charge by pound but rather by fill.

 

[passedpawn]

Too much capability should be a problem since you can adjust the flame.

*I meant "shouldn't".

 

[b-boy]

The only true test is to weigh your tank, brew, then weigh it again. Do this for a few brew sessions and you should gat a pretty good accounting of your propane usage.

 

[firerat]

I tried figuring this out and it made my head hurt.

Is it windy out?
What's the ambient temperature?
What's the temperature of your water?

Screw it. I bought 2 propane cans. When one empties out, I get it refilled right away.

I do know I get at least 2 brew out of one can. I've gotten 3 before.

 

[azazel1024]

I tried figuring this out and it made my head hurt.

Is it windy out?
What's the ambient temperature?
What's the temperature of your water?

Screw it. I bought 2 propane cans. When one empties out, I get it refilled right away.

I do know I get at least 2 brew out of one can. I've gotten 3 before.

Agreed. Conditions (humidity, temp, wind, sun), the size of the brew, how vigorous a boil, etc. all vary.

I typically do 60 minutes boils unless I am going pilsner heavy, then I do 90 minute boils. On a 19lb propane cylinder with my 160k BTU burner I typically get around 6-7 total brews of roughly 4 gallons each out of it before the cylinder is dry. A 30 gallon batch is obviously going to require a lot more propane, but you also are going to dissipate less heat per volume because of the lowered surface area relative to volume compared to a 4 gallon batch.

If I were to take a wild ass guess, you might get 3 brews, possibly 4 out of a "standard" 19lb cylinder for a 30 gallon batch.

I personally keep one cylinder just for brewing and if that one runs out during a brew session I swap in the propane tank from my grill and I'll just go swap the empty at my earliest convenience then.

Only time that gets tricky if I know both my grill and my brewing cylinders are close to empty. But if I have to I can always fall back on my electric range inside.

 

[ruger988]

I tried figuring this out and it made my head hurt.

Is it windy out?
What's the ambient temperature?
What's the temperature of your water?

Screw it. I bought 2 propane cans. When one empties out, I get it refilled right away.

I do know I get at least 2 brew out of one can. I've gotten 3 before.

Wow, really? I get at least 5-6 regularly (even in winter). Wonder what we're doing different (are those 10 gallon batches perhaps?) I keep acquiring tanks too, think I have 6 now, usually have two or three full at a time, haha.

 

[firerat]

Wow, really? I get at least 5-6 regularly (even in winter). Wonder what we're doing different (are those 10 gallon batches perhaps?) I keep acquiring tanks too, think I have 6 now, usually have two or three full at a time, haha.

My burner is kind of old and on its last legs. I probably lose a lot of efficiency because of it. I dunno.

Or I'm a dummy and actually am getting 4 or 5 brew sessions out of a can. With all the other notes I take, I really don't pay it much mind to how much propane I use. I should change that.

 

[VladOfTrub]

Here, so your heart won't hurt.

One gallon of propane is burned in one hour, with a burner rated at 95K BTU. Regardless of what it is heating.

You can't use the one pound one degree thing. Because it takes about 950 Btu/Lb to change state. On top of the BTUs needed to go from starting temp, up to change of state.

So, around 37K Btu/Hr. will be needed to raise the water tempertature through the delta T.

Then, to change state: weight X 950 Btu/Hr = BTU per hour needed to change state.

The burner that would be needed to crank that much water from room temperature to change of state, in one hour, would have to be about 280K Btu/Hr. About 3 gallons of propane will be burned.

I wasn't aware that the only numbers needed to figure out how many Btus per hour it would take to make water boil in an hour is: Delta Btu/hr x .25. To think, James Watt must have lied.

 

[b-boy]

Wow, really? I get at least 5-6 regularly (even in winter). Wonder what we're doing different (are those 10 gallon batches perhaps?) I keep acquiring tanks too, think I have 6 now, usually have two or three full at a time, haha.

If you trade in a tank around here, you only get 15 lbs in the new tank. If you take it to a fill station, you get 20 lbs. That could account for the difference.

 

[azazel1024]

If you trade in a tank around here, you only get 15 lbs in the new tank. If you take it to a fill station, you get 20 lbs. That could account for the difference.

Around here its about 19lbs for a filled tank or 15lbs on an exchange.

The only problem is that the handful of filling stations all charge $5-6 to fill, plus the going rate of propane. Which usually means if you go somewhere cheap to exchange, it might be $20 for 15lbs of propane...but it is generally around $24 with a fill up for 19lbs.

Roughly the same cost

Oh well. I tend to fill them instead of exchanging, but it depends on what side of town I am on when I need a new tank as there are only two places near me that I know of where I can get a tank filled, but about 20 places I know of where I can get an exchange.

 

[azazel1024]

The other difference could be if you are using hot water to fill your kettle for mashing or using cold/room temp water.

Other than Pilsners where I need very low mineral content, I use my tap water for all my beer as it is a nice slightly hard, slightly acidic water so it works okay for most types with only a small amount of modification and for Pilsners I just mix 2/3rds distilled water to 1/3rd tap water.

Anywayyyyyyy, I only recently started using hot tap water to fill my kettles for mashing and what not. MAN does it make a difference in heat time to mash. I get ~118F at my kitchen tap once I let the hot water run for a minute, where as in the summer I get 64F for the cold tap or 60F in the winter.

Cuts my heating time in half to get to mash temps and probably cuts a good 10% off my propane use or electric use if I am using the stove top (water heater is a lot more efficient than the stove top or propane burner). Not sure why it never occured to me to use hot tap water instead of cold tap water, but it did recently.

 

[oakbarn]

We do one barrel brews and it takes two full propane tanks for the brew session, one for the BK and One for the HLT. We can use the HLT maybe for another half Brew session. We get our tanks refilled up to the 20 lb limit. One issue that you will have with a High Pressure High BTU burner is that the Tank will not allow you to use all of the propane in the Tank. It will have quite a bit left when you get to a point where the flame does not respond to flow adjustments and the flame has become weak. You may also have "freeze" problems with the tank if you crank out the propane. All that being said, the Bigger the Better!

We have the Bayou Classic KB 4 burners. it takes about an Hour to get 30 gallons of 70 degree water to 180.

 

[b-boy]

Around here its about 19lbs for a filled tank or 15lbs on an exchange.

The only problem is that the handful of filling stations all charge $5-6 to fill, plus the going rate of propane. Which usually means if you go somewhere cheap to exchange, it might be $20 for 15lbs of propane...but it is generally around $24 with a fill up for 19lbs.

Roughly the same cost

Oh well. I tend to fill them instead of exchanging, but it depends on what side of town I am on when I need a new tank as there are only two places near me that I know of where I can get a tank filled, but about 20 places I know of where I can get an exchange.

This is why I switched to NG. I was spending a fortune on propane. Getting a fill is a pain around here. There is only one place I can go to that's close and they have weird hours.

I have 3 tanks plus the one on my grill and I was always running out. I can't tell you how many times I went to grill and realized I was out of propane.

 

[azazel1024]

I wish. Not NG lines in the ground around me and if I want a tank of NG...going to be big and expensive. Cheaper than propane, but a lot of hassle.

The way I look at it, I am maybe spending $3-4 a brew session on propane maybe. Most of my beers (ignoring sunk equipment costs, which will pay off someday. Right? Right? Why do I only hear crickets?) end up costing a lot less than I would have paid for them at the store.

I think I am averaging around $26 in ingredients for 4 gallons of beer for roughly a 6% ABV brew. Obviously +/- a few bucks if it is an IPA, or fruit beer or what have you. Higher or lower ABV again pushes it +/- on cost. Even throwing in $4 in propane to make said beer and it's only $30 for maybe 35-40 bottles of beer (take out yeast losses). $1 a bottle is quite a bit less than beer is around me (other than cheap/crap beer). With tax it is typically around $6.40 for a six-pack of "cheap" beer. Even at case rates, about $13 for a case with tax. For a generally good beer that I'd probably consider on par with my brew (or, gasp sometimes better than my brew) it is going to typically be more like $8.50-11 for a six-pack after tax.

Mine comes out to $.80-85 per bottle once everything is included (gas, ingredients, bottle tops, sanitizer, etc.). Maybe call it $.70 a pop if I do it on my electric range (about $.30-.50 or so worth of electricity).

I love to save money where I can, but I'd also rather save time and make things easier. My propane burner saves a lot of time over my range and it is a lot easier too.

If I could easily find a way to get something like a 100# NG tank delivered and convert my burner to NG I would be ALL over it, but there just doesn't seem to be a cheap/easy way to do that around me (it is cheaper than propane, but not cheap enough to be worth the hassle).

Really in a couple of years I plan to go to an E-HERMS system once I have the extra space and money to invest in it. That will save a fair amount.

 

[william_shakes_beer]

I have one cylinder. My local warehouse/club grocery store charges by the gallon for propane, not by the fill. I heat to dough in temp, cut the burner off, dough in and check the frost line on my tank. If its in the lower half (below the seam) i top off the tank during mash time. When I first started using the KAB burner, I got 4-5 batches at 5 gallons out of each cylinder.

In the summer time
when the weather's hot
you can stretch right up
and touch the sky
when the weather's fine
..... you know the rest

 

[--Dom--]

I was gonna say just fill your tank at U-Haul.... But then I saw that you're in Spain so....