2.5 lb Co2 tank. How many cornys?

[Grad]

Hi,

I'm just getting into kegging and am repurposing a chest freezer to a keezer using an inkbird temp controller.

Still figuring things out but to be able to fit 3 5 gallon corny kegs, I can only fit a 2.5lb co2 tank inside and don't want to do any drilling to leave the tank outside the freezer.

I'm wondering, from peoples experience, how many kegs roughly can be carbonated AND served with a 2.5 lb tank? Obviously assuming no leaks or anything.

I'm thinking that if I can't carb and serve 3(5 gallon) kegs per tank then I'll probably just get a 5 lb tank and only put 2 kegs instead of 3.

I've been using a different fridge to do 2 kegs at a time and it's so great! Cant believe I bottled for so long!

Thanks,
Grad

 

[IslandLizard]

Welcome to kegging! Yeah, what took you so long?

Get a bigger tank (20#) and put the tank outside your keezer. Tank refills or swaps are relatively much more expensive for smaller tanks. Call around in your area to get the "lay of the land" in CO2 business. Source a used tank, since swaps are most common now, so a $$$ brand new shiny (empty) tank will be traded for a used full one on day 1.

The only advantage of small(er) tanks is that they are a bit easier to move around, such as to parties or beer events.

 

[madscientist451]

Getting your CO2 in the small tanks will cost you more. A 20lb tank exchange costs slightly more than a 5lb tank exchange and your get 4 times the CO2. I don't leave my kegs hooked up to the gas all the time and a 20lb tank lasts for 6 months or more, but I'm running a pretty small volume of kegged beer. You can also save a little CO2 by naturally carbonating in the keg. Just add priming sugar like when you are bottling and leave the keg in a warm place until it carbs up. As you pour the beer out, you'll have to top up the C)2 a few times to maintain pressure.
Getting a 20 lb tank for purging/topping up the kegs and another small tank for inside the chest freezer might be an option that works for you.
I got all my tanks and regulators cheap on craigslist.

 

[ScrewyBrewer]

I'm wondering, from peoples experience, how many kegs roughly can be carbonated AND served with a 2.5 lb tank? Obviously assuming no leaks or anything.

I'm thinking that if I can't carb and serve 3(5 gallon) kegs per tank then I'll probably just get a 5 lb tank and only put 2 kegs instead of 3.

I like the portability of 5 pound tanks when serving beer from kegs at parties, and keep a spare on hand to prevent running out of Co2 at the worse possible time. The empty weight of your Co2 tank is stamped into the side of the tank. It is a good practice to weight your tanks when full and again when you think they are running low. I can tell you that on my setup a 5 pound tank can easily carbonate and serve more than half a dozen corny kegs.

 

[bracconiere]

i use 1oz to purge, 1.2ozs to carb....(16x2.5)/2.2=18 i think?

edit: usually they only fill my 20lb tank to 18 lbs though, so YMMV....edit again...another 1.2oz to serve....so 11...

 

[IslandLizard]

1 pound of liquid CO2 yields 8.72 cubic feet (= 65.26 US gallon) of CO2 gas at standard atmospheric pressure or 14.7 psi (1 atm) and 25°C (77°F).

So a corny keg with a volume of 5.25 US gallons takes 5.25 / 65.26 = 0.0801 pounds or 1.28 oz (say, 1.3 oz for ease of calculations) of CO2. At atmospheric pressure.

For example, 100% liquid pre-purging a Starsan or water filled keg (filled to the brim) will thus take about 1.3 oz of CO2, if left with no overpressure. IOW, showing 0 psi on your regulator at the end of filling it. If you leave it filled with CO2 showing 14.7 psi on your regulator, it would be double that amount, 2.6 oz of CO2.

Carbonating with 1 volume of CO2 is exactly that, you dissolve 1.3 oz of CO2 in your keg with 5 gallons of beer. Carbonating at 2.5 volumes will use 2.5 * 1.3 = 3.25 oz of CO2.

Plus the volume of CO2 required to push it out of your keg when serving. Say, when serving at 14.7 psi, that will take 2x that keg volume, or 2 * 1.3 oz = 2.6 of CO2.
When your beer runs out, that will leave you with an "empty" keg filled with 14.7psi of CO2 (=2.6 oz). You could use that to pre-purge another keg, if you're frugal.

So in total it takes 1.3 + 3.25 + 2.6 = 7.15 oz of CO2. That's the best scenario.

Let's round that up to a total 8 oz due to some other routine CO2 handlings, so you end up using 1/2 a pound of CO2 per keg, pre-purging, carbonating, and serving. More likely a bit more.

 

[bracconiere]

Carbonating at 2.5 volumes will use 2.5 * 1.3 = 3.25 oz of CO2.

you're forgetting residule co2?