Carbonation in the closet question...

[Slipgate]

Background:
I got another regulator and 5lb CO2 bottle so that I can carbonate beer in the closet while the kegerator is full. I put a beer keg under pressure in the closet at serving pressure. I expect it will fully carbonate in a week or so. It won't go in the kegerator for another month probably.

Question:
The beer is now around 72 degrees. It will carbonate at this temp. It is set at 15psi which is serving pressure for this beer. Once I add it to the kegerator and the temp drops to 40, what can I expect to happen to the carbonation level? Will I need to wait a few days longer to get the carbonation up?

 

[Kealia]

Short answer = yes.

Carbing at 72 degrees will allow very little CO2 to actually absorb into the beer.

Check out this chart (which doesn't even get to 72).
At 65 degrees and 15psi you'd hit ~1.7 volumes but when you drop the temp to 40 it's going to carb to ~2.75 volumes so it will take some time to absorb that extra CO2 into the beer and carb up.

 

[audger]

you can fully carbonate the beer to the correct amount as long as you match the pressure to the temperature, according to the carbonation chart.

if the temperature changes, you must change the pressure accordingly to maintain the same level of disolved CO2.

 

[JuanMoore]

Since the chart linked above doesn't go up to 72°, use a calculator like the one at the bottom of this page to determine the pressure you need to use for your desired carbonation level. I'm going to guess that you're shooting for 2.75 vol since your serving pressure is 15psi and you keep your kegerator at 40°. That level of carbonation would require 34.1 psi at 72°. Once the beer's carbed up in a couple weeks, I'd let it chill in the kegerator overnight to allow the pressure in the headspace to reduce to serving pressure before putting the gas on it at serving pressure.