How much should the tank pressure

go down when you move it from room temp to the fridge? Mine went from 800 to just below 600. It's nearly in the red refill area and its a brand new refill.

Also, how cold should a fridge that is new get when set on the lowest setting? I've got my controller set on 40 F and its running constantly and only getting to about 45 F

Thanks,
Al

600 sounds right on to me, it really all depends on the temp in your fridge. Remember, psi is NOT an indication of how much gas is in the tank; the pressure will remain fairly constant and your gauge will not move much until the tank is empty because then there will be no pressure. The only way to know how much gas is left is to weigh the tank and subtract the tare weight printed on the side.

Your CO2 tank's high pressure gauge is useless. Why? Bottled CO2 is stored in a liquid state and evaporates to fill the empty space above it at a pressure equivalent to the vapor pressure of CO2 at the temperature inside the bottle. In layman's terms; the HP gauge will *always* read 800-1000psi when warm and 4-600 when cold. Even if your tank only has one tsp of CO2, it will read 4-600 until that tsp is gone. Then it will go from 400 to < 100 like a falling rock. This is also why propane tanks on grills/RV's/etc do not come with pressure gauges to determine their fill level.

It's not completely useless - it does at least give you a heads-up a day or two before your tank goes empty on you if you're only pouring a couple pints a day.

Buford said:

It's not completely useless - it does at least give you a heads-up a day or two before your tank goes empty on you if you're only pouring a couple pints a day.

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True, but it's accuracy is poor enough that it will leave you stranded in a pinch. If you have company over it can read 600# when they arrive and 0# just 15 minutes later. Or it can read 600# and you plug it up to an empty corny to purge and it's dead in about 10 seconds.

In any case, the most important point that newbies need to take away from this thread is that the HP gauge in not a "gas gauge"...

My rule is plan on getting a re-fill at 300 psi. At that point, there isn't any liquid CO2 in the bottle, so you're running on vapors.

What about the PSI to the keg? I noticed it drops as well when the tank gets cold...

That's just your regulator stiffening up. There's a spring and diaphram in there that probably get affected by cold a bit. Readjust and it should stay.

200-300psi sounds reasonable for assuming you need a refill. you can always weigh the tank and subtract the Tare weight stamped on it to know how many lbs of liquid (if any) are left.

and Bobby's totally right about the cold affecting the output psi. think of it like a cold weather break-in. you might have to nudge it up once or twice after it cools, then it should be steady if the regulator is working right.

Yeah, I posted that question after one too many homebrews and didn't truly think about the science behind air pressure. Pressure decreases when it gets cold and of course, increases when heat is applied. I did increase the pressure to the keg once I noticed it went down and it has remained steady. Ok, now that my work day is over and I don't have to use my mind anymore tonight, I am going to imbibe a plethora of homebrews... CHEERS!

if you wanna know how much liquid co2 remains, pull the tank out of the fridge and let it start warming up. The only gauge you need is your hand. the liquid co2 will stay colder longer. Just rub your hand down the side of the tank and when you feel a temp break, that's the level of the liquid. This works with any gas that's compressed into a liquid in a tank (ie propane, oxygen, etc.) With these tanks, just run your hand down them while they are "running". the evaporation of the liquid cools above the liquid surface more than the lower part. Works WAY better than that silly gauge.

I always keep a dozen of those 1 oz co2 carts around just in case. Four of those can empty an entire keg.

BeerAg said:

I always keep a dozen of those 1 oz co2 carts around just in case. Four of those can empty an entire keg.

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How do they hook up to the gas post?

I've got the 12 gram CO2 charger. Remind me to show it to you Sunday.