Co2 Regulator - Temperature Affects Reading?

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WitWonder

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OK I've searched and can't find an answer on this one. I've been kegging a while now and have stored my co2 bottle in the fridge initially with no problems. I then used it for quite a while with it sitting outside the fridge and again, no problems. I've just finished a freezer conversion and have gone from having the co2 bottle outside to inside the freezer, and have noted that the side of the regulator which measures gas remaining is significantly lower than what it was last night (like 50% less). I had left the gas off overnight and set the freezer to 2degrees, turned on the gas again this morning to put some pressure in the kegs and it's still reading as though it's half empty :(

Obviously the regulators have an operating range and I'm hoping that's its reading incorrectly because it's too cold, rather than me losing gas (again) having only refilled it 2 weeks ago. Is this a possibility?
 

np1962

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While not wanting to comment on whether you are losing gas I will say that I had my keg fridge in the garage for a while and noticed that when the temp was hot here, high 30's- low 40's my regulator read higher than it had when the temp was in the 20's a couple of days earlier.
Therefore I would say temp does change the pressure of the CO2 in the bottle.
O/T My keg fridge is now in the house at a constant temp :D

Cheers
Nige

Edit:- I have a recollection that if the bottle is filled while cold you actually get more in. Could be wrong though.
 

katzke

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Could be a leak or the change in temp. From what I know that side of the gauge is not very reliable because the CO2 is in a liquid state. It only measures the pressure the liquid puts off and not how much liquid is in the tank. The colder the liquid the lower the number.

So to see how much is in the tank you need to weigh it. Some place near the top will be a number that says how much the empty tank weighs. In my case it is marked TW 11 LB 12 Oz. On my electronic scale it came in at 18.52 pounds so I got a bit more then the 5 pounds I purchased. I was smart and weighed the tank and the regulator/hose so I do not have to disconnect it when I check.

Not sure how they mark the bottles down there but it must be similar only in that infernal metric system you use.
 

crundle

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I noticed the same thing when I had my bottle in the kegerator, it seemed to have less gas than it did before, but once out again in the heat, it slowly returned to the previous reading.

My limited understanding is that it has to do with the temperature, the lower the lower apparent pressure, but this will not affect your settings. Recently mine has returned to outside the kegerator to allow for another keg, and in the recent 40 degree weather, it was reading well over a 1/4 higher than it had when the temperature was in the mid 20's.

cheers,

Crundle
 

WitWonder

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Hmm ok thanks guys. Good to know I am not going crazy.... at least that's what the voices in my head keep telling me. :wacko:
Got a big shindig planned for Oz day and need all the gas I can get!
 

Adamt

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It's likely just the change in temperature which affects the headspace pressure in the tank. More CO2 will existi n the liquid phase at lower temperature and hence a lower headspace pressure.. The headspace pressure is what is measured by the regulator to indicate "how much is left".

What where the unrefrigerated and refrigerated readings?
 

tallie

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I experienced the same thing when I put my 6.8kg cylinder in the fridge once. I was quite surprised to see how much the pressure dropped by (about half) and assumed there was a leak at first, but I was relieved to find the gauge returned to normal when I put it back outside the fridge. Before that, I was using soda-syphon cylinders and didn't notice any difference on the gauge between storing it inside or outside the fridge.

Cheers,
Kris.
 

Gulf

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For an ideal gas:
PV=NkT
where P is Pressure, V is Volume, N is number of gas molecules, k is Boltzmann's constant, T is Temperature.

V, N, k are all constant in this situation, so P is directly proportional to T. That is, double the temperature of the gas (in degrees Kelvin) and you'll double the pressure of the gas.
From fridge to room temperature should be about a 7% change in the reading on the dial.

You're not losing any gas - your cylinder will still carbonate just as many kegs!
 

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