Force carbonate half full keg

[Qcbrew]

Hey guys,

I'm looking into setting up a keging system. Thing is, I often brew 2.5 gal batches (stove top/BIAB), but I also have a 5 gal electric system. I would like to buy only one keg size. If I force carbonate a half full keg, will I need to use more or less CO2 to get the same carbonation I would get in a full keg?

Way I see it, since dissolved CO2 is a function of the partial pressure (Henry's Law), a higher air volume would require more CO2 to reach the same pressure. Anyone has some first hand experience with this?

 

[day_trippr]

You'll use less CO2, because the beer requires ~2.5 times the CO2 to carbonate than what will occupy the empty half of the keg

And the proper CO2 pressure to reach and maintain the desired carbonation level would be unchanged from carbonating a full keg or a half keg or a quarter keg.

Also, I don't think Henry's partial pressure law has anything to do with this, unless you were using beer gas...

Cheers!