Carbonating 3 gal in a 5 gal keg

[wazzu1991]

I've searched the forum and I can't find the right answer for this one...

I brew 3 gallon batches because I like the smaller size as I am the only beer drinker in the house and I can brew more often. I have a mini fridge that holds one keg, (5 gal). I have two 5 gallon kegs and don't really want to spend the cash on a couple of 3 gallon ones. I would like to carbonate one with sugar while I am drinking the other. I only have room for one in the fridge. I can purge the air out of the keg but I can't figure out how much priming sugar I need to carbonate 3 gallons in the 5 gallon keg. It seems to me that I would need extra to make up for the head space in the larger keg. I usually use 2 5/8 ounces to bottle condition a 3 gallon batch.

 

[hoppymonkey]

It is actually less in a keg b/c of the physics. I have never added sugar to a short batch in a keg, but on average a 5 gallons batch in a keg only needs 1/3cup of corn sugar. Also, if you are force carbing the additional head space actually carbs the beer faster. Maybe someone else knows your exact answer.

 

[NuclearRich]

I've also been wondering about this, and most searches I have made turned up answers about fermenting. I have a 15gal Sanke and want to throw fermented beer into it, but I am also unsure of either the force carbing or natural carbing methods.