does force carbing kegs just eat c02?

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mikesalvo

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I have 2 kegs force carbing in my kegerator. I put a fresh 5 gallon tank in there yesterday, and after 24 hours of 30 PSI (on 2 Kegs) the gas level has dipped out of the green "full" area on my regulator. Could it be that force carbing eats so much gas, or could it just be that my regulator is IN my fridge?
 
Not useless, but the high pressure reading will drop a lot with lower temperature. Check the wiki for details.
 
The high pressure gauge is temp sensitive. Liquid co2 is always at a constant pressure for a given temp regardless of how much co2 is left in the bottle. Putting the bottle in the fridge dropped the pressure.

Force carbing does use lots of co2. But that is not what you are seeing on the gauge.
 
Even if you didn't force carb, just stuck the tank in the frigde the CO2 gauge will drop drastically in about a day. After that it stabilizes.
 
nice, thanks! Does the same go for the PSI reading? IE: are both the "level" and "PSI output" useless in the fridge?
 
Both gauges work in the fridge. It is just that the information you can get from the high side gauge (tank pressure) is limited. The high side pressure will drop rapidly when empty. It will stay the same until then.

The low side pressure (regulator output) is useful to you to select how much co2 you want in your beer.
 
badbrew said:
Yes, force carbing uses lots of co2.

That's just not accurate. Unless you are venting the hell out of it you are not gonna waste a bunch of co2.

The only way to carb and use less co2 would be to prime with sugar or whatever your choice of fermentable.
 
My first 5 lb tank just bit the dust a bout a month ago after carb'ing and serving about 10 cornys. The "pressure level" gauge drops dramatically when put into the fridge as mentioned before, however, it doesn't seem to change at all for the rest of the life of the tank. When it does start to drop though, its drops quick and you are out of CO2. So just know that if you see it start to go down you don't have much time.
 
FWIW a general rule of thumb is that each pound of CO2 will carbonate and serve between one and two corny kegs depending on carb level, how much you use when purging kegs, etc. That means your 5# tank should get you through 5-10 corny kegs before needing to be refilled. Be aware that a lot of places don't fill the tanks completely though, especially true for LHBS. That's one of the reasons I prefer to do a swap at the welding shop, I know I'm getting the full 20# I paid for.
 
What Juan said. 1-2 kegs per lb. However, that is if you have a buttoned up system with no leaks. Even the tiniest of leak can eat through co2 quickly. I tested my system for leaks with star san and soap water and found no leaks. I have a 20lb tank and only got about 4 kegs worth of carbing/serving over about 2 month period before empty. So, needless to say, I had a VERY slow leak. I've now redone my system and am hoping this 20lber will give me a good baseline for number of kegs to carb and serve.
 
The only way to know how much CO2 you're using or have used is to know the tare weight of the tank and then compare that to the present weight. That's how I know how much I'm getting when I get the tank filled.
 
My first 5 lb tank just bit the dust a bout a month ago after carb'ing and serving about 10 cornys. The "pressure level" gauge drops dramatically when put into the fridge as mentioned before, however, it doesn't seem to change at all for the rest of the life of the tank. When it does start to drop though, its drops quick and you are out of CO2. So just know that if you see it start to go down you don't have much time.

The reason you get this is because the gauge is reading the air pressure in the tank, but the CO2 is liquid inside. So it doesn't matter how much liquid CO2 you have, the air pressure will always be the same. Every little bit of air let out of the tank allows a little bit of CO2 to go from liquid to gas. However, once you run out of liquid CO2, that's when it drops off a cliff because now you can't replace that air pressure. That's why Bobby mentioned weighing the tank, that way you can weigh the amount of liquid CO2 you have left. I'm sure someone with more know-how than I could devise a scale and weight system to measure CO2 levels (I think I saw one for cornys), but I prefer to just ignore whatever the tank gauge reads, at least until its empty and I can't pour anymore beer.
 
The reason you get this is because the gauge is reading the air pressure in the tank, but the CO2 is liquid inside. So it doesn't matter how much liquid CO2 you have, the air pressure will always be the same. Every little bit of air let out of the tank allows a little bit of CO2 to go from liquid to gas. However, once you run out of liquid CO2, that's when it drops off a cliff because now you can't replace that air pressure. That's why Bobby mentioned weighing the tank, that way you can weigh the amount of liquid CO2 you have left. I'm sure someone with more know-how than I could devise a scale and weight system to measure CO2 levels (I think I saw one for cornys), but I prefer to just ignore whatever the tank gauge reads, at least until its empty and I can't pour anymore beer.

This is correct, but you keep using the word "air" when you really mean "gas" or "CO2" :p

In the CO2 cylinder you have liquid and vapor CO2 in a nice happy equilibrium. As erikpete pointed out, as long as there's some liquid you're going to maintain the same vapor pressure inside the tank. As soon as the liquid runs out the tank pressure will start dropping.

The vapor pressure of liquid CO2 (like the vapor pressure of any liquid) is highly temperature dependent:
http://en.wikipedia.org/wiki/Carbon_dioxide_data#Vapor_pressure_of_solid_and_liquid

If you look at the warmest 2 points on that chart you'll see that at 22 degrees C (room temp) the pressure inside your tank should be 45,600 mm Hg (=882 psi) and at 6 degrees C (roughly kegerator temp) the pressure is 30,400 mm Hg (=588 psi).

So you should see a significant drop in tank pressure when it goes from room temp to fridge temp! That doesn't mean there's less CO2 in there, it just means the vapor pressure dropped with temperature.
 
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