Cold CO2 Tank

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zythe84

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I'm about to set up my first keezer, and I know that when you put the co2 tanks and regulator in the freezer, it will lower the pressure reading of the "amount left in the tank" gage, but I'm curious at to whether the cold temperature will also affect the reading of the pressure going into the keg. If I set my regulator at 12 psi at the cold temp, can I trust that 12 psi will be going into the keg, or do I need to adjust for the temp?

Thanks,

Zythe84
 
Nope. It lowers the gauge reading on the high pressure side because the colder temperature actually causes there to be less pressure in the CO2 tank. This happens because there is the same volume in the tank at a lower temperature so by the ideal gas law the pressure has to decrease.

Your kegs will take more volume at a lower temperature to achieve the same pressure, but the regulator will supply the correct (gauge) pressure to the kegs independent of temperature.
 
You may have to adjust the regulator a couple times the first day, but after that the pressure will be stable.
 
Ok, Thanks guys...my concern also. But as far as the reading on the "amount remaining" side....how reliable is that? I noticed that my full CO2 tank (that I checked and does not leak) registered quite a bit lower after hooking it up to the keg (again, no known leaks). Other than it actually starts to drag when trying to draw a cool one, I really don't trust the reading the gauge is giving me. The LAST thing I want is to run out of CO2 on a weekend afternoon when I can't do anything about it! I do have a back up tank that I keep filled, but would really like to be able to trust my gauges to know when I'm getting low so I don't have to open up the kegger and lose cooling just to switch a tank in mid stream. Would rather switch the night before! Lovin this site, btw!
 
UKFreak said:
Ok, Thanks guys...my concern also. But as far as the reading on the "amount remaining" side....how reliable is that? I noticed that my full CO2 tank (that I checked and does not leak) registered quite a bit lower after hooking it up to the keg (again, no known leaks). Other than it actually starts to drag when trying to draw a cool one, I really don't trust the reading the gauge is giving me. The LAST thing I want is to run out of CO2 on a weekend afternoon when I can't do anything about it! I do have a back up tank that I keep filled, but would really like to be able to trust my gauges to know when I'm getting low so I don't have to open up the kegger and lose cooling just to switch a tank in mid stream. Would rather switch the night before! Lovin this site, btw!
Click to expand...

In my experience, the "amount remaining" gauge is basically worthless if you store the tank cold. My full tanks are already bordering the red zone. It will suddenly drop when it's pretty much toast, but it's usually too late by then. I came across a free tank not long ago, so I keep that one full just in case I run out when people are over. I get at least 5 kegs from my 5# tank though.
 
Hi

CO2 is strange stuff. They actually put liquid CO2 in the tank when they fill it. The liquid boils off and creates the gas in the tank. Like any liquid, it creates a large volume of gas when it boils.

The pressure valve just shows the pressure at which the liquid is currently boiling off. Lots of liquid boils at the same pressure as a little liquid. The pressure does very much change with temperature.

If the temperature does not change, the pressure gauge will sit there right at "full" until the liquid almost all boils off. Then the pressure will start to drop. Not very useful to let you know when to order a new bottle. A *much* better way to check the tank is to weight it.

Bob
 
OK, thanks guys! That was kinda what I thought. Seems the easiest thing might be like ByrceL said, just keep a spare on hand. My current kegger is a 2-tap tower (cool as hell! Built from all new stuff. Gonna post a pic ASAP!) but right now only have a 5 lb tank. Thinkin about either a 15 or 20 lb and keep the 5 as a bail out bottle. Learned the hard way that just because the gauge says low don't mean you're out if it's cold. Local guy(who knew the situation) told me I needed a swap-out for my first tank....2nd one with same reading is working on it's 2nd keg....needless to say he won't be getting any more of my business.
 
Hi

Having two tanks the same size is sometimes a good idea. That way you really don't care which one is empty at any given time. Five pounds of CO2 will last for a lot of kegs unless you have a leak or are doing a *lot* of forced carbonation.

Bob
 
The ideal gas law doesn't apply to the CO2 in your tank because, as pointed out above, the CO2 in the tank is a liquid and not a gas.
 
physfarm said:
Nope. It lowers the gauge reading on the high pressure side because the colder temperature actually causes there to be less pressure in the CO2 tank. This happens because there is the same volume in the tank at a lower temperature so by the ideal gas law the pressure has to decrease.

Your kegs will take more volume at a lower temperature to achieve the same pressure, but the regulator will supply the correct (gauge) pressure to the kegs independent of temperature.
Click to expand...

+1

Also, don't get too wrapped up in the numbers when somebody says they serve at this or that psi - that's the correct pressure for a good pour ON THEIR SYSTEM. Just make sure your serving line is long enough to provide enough resistance so that you don't get a lot of foam - I would say 5 feet at the very least. Mine is 6 feet and my serving pressure is usually around 13 psi with temp around 38F. I get a good pour with a good, long lasting head and good carbonation. You'll get yours dialed in after a couple tries.
 
Thanks, folks! My kegger (for now, at least) is running commercial kegs and it works well at about 8-10. As soon as I get a few batches under my belt, I'm gonna switch at least one to a homebrew. Thanks to fatbastard, I'm already thinkin about steppin up my system to handle about a dozen or so homebrew kegs! LOL
 

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