Co2 usage

[deuce40]

Im want to start kegging soon and was wondering if i only put 3gallons of beer into a cornie, will it use more co2 then if i were to fill it up all the way. My thinking is if was filled all the way it would take more to pressurize then if completely full. Is this right?


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[NTXBrauer]

It will require more CO2 to fill the empty head space and reach the required PSI, if the corny is only filled with 3 gal vs. 5 gal of beer.

 

[deuce40]

So usage will increase also or will i still be using the same amount as if it were five gallons?


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[Beer_Eugenics]

It would depend on how you force carb it. If you use the set it and forget it method it would use less.

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[IvanTheTerribrew]

So usage will increase also or will i still be using the same amount as if it were five gallons?


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You will need more co2 to fill the head space and for purging the keg. With that much headspace I would def recommend not to skimp out on purging because that's a lot of headspace to have air.

Once you have your headspace filled with co2, your operation of the keg will be almost the same as if it was 5 gal. Whether you use the set and forget method or force carbonating method. Either way you're trying to get X amount of volumes CO2 into your beer. And the same can be said for when you dispense beer. You will be only using the CO2 to fill the space that you remove when you pour.


- ISM NRP

 

[NickN72]

You will have less co2 used in solution with the beer, but probably lose a little more co2 in purging the large headspace.

All together I would say you'll probably use about the same amount of co2 as you normally would with a 5 gallon keg. You'll use more co2 per gallon of beer, but the total co2 used in carbing/dispensing the keg should be about the same.

 

[masonsjax]

The headspace increases as you drink a keg, so 5 gallons is eventually 3 gallons. You're just skipping over the first 2 gallons.

 

[day_trippr]

Even though I've never partially filled a corny (I'm way more likely to fill above the gas dip tube!) for some reason I was curious about this.

Intuitively it seemed like the net CO2 usage to properly flush, carb and dispense a keg starting with 5 gallons would be very close to equal to that used for 3 gallons in the same keg. But I couldn't make up my mind which would in theory use more CO2. So I thought I'd give the math a try right here, right now.

So assume 5 gallons in a corny leaves roughly two quarts of headspace, after filling and lidding the keg you fill that volume with CO2 and release it three times, you're carbing to 2.5 volumes, and with no change in CO2 pressure (ie: purging pressure = carb pressure = dispensing pressure).

So it takes 2 gallons to flush and then refill the headspace, 2.5 x 5 gallons to carb, and 5 gallons to dispense for a total of 19.5 gallons or 2.60 cubic feet of CO2 at pressure.

Starting with 3 gallons you'd have 2.5 gallons of headspace, use 7.5 gallons to carb, and use 3 gallons to dispense. Four shots of CO2 to flush and fill the headspace = 10 gallons, plus 7.5 gallons to carb to 2.5 volumes, plus 3 gallons to dispense, for a total of 20.5 gallons or 2.75 cubic feet.

Unless I missed something (quite possible - going from sealed to unsealed model during the purging could mess that part up) that's pretty darned close. That 3 gallons would use more gas reflects the power of multiplication

Cheers!

 

[Beer_Eugenics]

Even though I've never partially filled a corny (I'm way more likely to fill above the gas dip tube!) for some reason I was curious about this.

Intuitively it seemed like the net CO2 usage to properly flush, carb and dispense a keg starting with 5 gallons would be very close to equal to that used for 3 gallons in the same keg. But I couldn't make up my mind which would in theory use more CO2. So I thought I'd give the math a try right here, right now.

So assume 5 gallons in a corny leaves roughly two quarts of headspace, after filling and lidding the keg you fill that volume with CO2 and release it three times, you're carbing to 2.5 volumes, and with no change in CO2 pressure (ie: purging pressure = carb pressure = dispensing pressure).

So it takes 2 gallons to flush and then refill the headspace, 2.5 x 5 gallons to carb, and 5 gallons to dispense for a total of 19.5 gallons or 2.60 cubic feet of CO2 at pressure.

Starting with 3 gallons you'd have 2.5 gallons of headspace, use 7.5 gallons to carb, and use 3 gallons to dispense. Four shots of CO2 to flush and fill the headspace = 10 gallons, plus 7.5 gallons to carb to 2.5 volumes, plus 3 gallons to dispense, for a total of 20.5 gallons or 2.75 cubic feet.

Unless I missed something (quite possible - going from sealed to unsealed model during the purging could mess that part up) that's pretty darned close. That 3 gallons would use more gas reflects the power of multiplication

Cheers!

Unless you purged three times then it would be 19 gallons for five gallons and 18 gallons for three. Nice wright up though never really gave a thought to what exactly volumes of co2 meant.