Co2 tank, inside or outside kegerator?

[Twinsbro]

Thanks again guys.

[dunleav1]

If your tank isn't aluminum and it's steel it will leave rust stains if you use it inside the fridge.
Not to mention it takes up space for a keg.

[bcmaui]

The regulator and tank may last longer if kept outside the cooler might be what they are talking about due to lower moisture.

Even if you have an alumimium tank, i suspect there the regulator has steel components that can rust faster inside the kegerator.

The amount of CO2 in the tank is the same, although at different temperatures the psi will vary for the same amount of gas.

[ajdelange]

In a nutshell: At colder temperature the CO2 gas (left after all the liquid has evaporated) will be denser so that at whatever pressure you stop drawing gas the amount left in the tank will be greater if the tank is kept cold. The ratio of the amount remaining cold to hot is the ratio of the Kelvin temperatures something like 294/273 (room temp vs. freezing) so it's not a lot - certainly not a enough that you would notice it lasting longer. Practically speaking it doesn't make any difference with respect to how much is left behind (wasted).

One advantage to storing cold is that if you take a cold bottle out of the cooler and the room is humid you will see a condensation line that tells you how much liquid remains.

WRT to filling cold: yes, you can get more liquid into the bottle that way but be careful. This is how one overfills a bottle. I've done it and the result is really spectacular. Don't ever fill a bottle without weighing it before (and making sure the "empty" weight is really the tare stamped on the neck) and after.

Note also that the PV = nRT analysis only applies after all the liquid in the bottle is consumed or when the temperature is above 87 °F, the critical temperature, and then not that well as CO2 is not an ideal gas except at very, very low pressure. While there is still liquid present the bottle contains liquid and gas and while the gas part will obey the ideal gas law, at least approximately, what determines the pressure in the bottle when liquid in any amount is present is the vapor pressure of CO2 which does depend on temperature but in a not quite linear fashion. The pressure in the bottle is approximately P = 302 + 5.662*T + 0.025*T*T psig when the temperature is in °F (it isn't linear when the temperature is in Kelvins either). Thus at 70 °F the pressure will be 823 psig and at 45 °F only 608. This is how you tell your bottle is nearing empty. The pressure gauge will hold steady (assuming steady temp) while the liquid boils off and once it is gone, start to drop as the gas is drawn off.

[ApresSkiBrewer]

Side note: I've recently been informed that most commercial spec's for serving pressure/ideal balance for commercial serving assumes the tank is at or near room temp, not fridge temps.

[ajdelange]

Sounds like a furphy to me. I suppose you might advance some argument about where the regulator is (though that should make no difference either and in fact in most commercial setups the regulators are on "panels" inside the cooler) but it certainly doesn't make any difference where the gas bottle is in terms of any physics I can think of though it's certainly more practical to have it outside in the sense that it doesn't take up room in the cooler which could be used for beer. Nor do I remember (key word) ever seeing anything about this in the ASBC gas tables, Practical Brewer or any other reference.