Hey guys. Kegging tomorrow! I know nothing about co2 keep in the mind, but my tank is at room temperature right now. I am going to keg my beer and set it to 30 psi over night. If I set it to 30 psi at room temperature and then get it down to 30 degrees or so, will my regulator change at all even though the temperature changes? Or no matter what temperature it's at, will I be ushing 30 psi into it?
You aren't kegging to a specific pressure. You are kegging to a specific volume of CO2. Figure out the volumes of CO2 that you'll be using, and then set your psi to match that, based on temperature.
Here is a chart:
http://www.kegerators.com/carbonation-table.php
and a calculator:
http://www.brewersfriend.com/keg-carbonation-calculator/
If you set the pressure at room temp (get an accurate measurement of room temp), you will have to disconnect, cool the keg, purge the keg, and then reconnect at the new pressure (determined, again, by volumes of CO2 desired and temp).
The pressure on your regulator will not decrease when you cool your beer. The pressure will stay the same regardless. What will change is your beer's solubility to gas (in this case, CO2). The colder the beer, the more soluble gases are in it. So, the colder you make it, the more CO2 will dissolve into your beer, if you leave the pressure the same. You want the same amount of CO2 in your beer, regardless of the temperature. This is why you must decrease the pressure if it is colder.
If you have a closed system (no air coming in/out, and no beer coming in/out), if you take a keg that was refrigerated and move it outside to room temp, the pressure in the keg will increase. This is because as the beer warms up, CO2 will come out of solution and increase pressure because the beer is less soluble to gases. Conversely, if you take room temp beer at a certain pressure at room temp and refrigerate it, the pressure will decrease as the beer gets colder, because the beer's solubility to gases will increase.
This basic concept is important, because you always set your pressure based upon temperature and a desired volume of CO2. In this way, you can carb your beer at any temperature, and then cool it to your serving temperature and know that you are good to go (assuming accurate pressure and temperature measurements).
