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Old 05-31-2012, 03:18 AM   #1
EliW
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OK, so riddle me this.

There are all these specific calculations that you are supposed to do to get your beer carb'd perfectly. Inject that 2.4 volumes into your beer while it's chilled at 45degrees, etc.

But I'm a little confused about something.

Basically everything I've read, talks about just serving your beer at 12PSI or so. But, doesn't that destroy your carbonation over time?

Because it seems that over time, if you hooked your keg up to a kegerator, that it would recarb at the 12PSI level. ... Either 'up' or 'down' over time.

Worse is if you take your keg to a party, and maybe have it colder in an ice bath, or warmer, just sitting out at 75 degrees. Where the pressure has changed.

...

So I guess I'm saying, should you really be serving at 12 PSI? Because won't that affect over time the remaining beer? Shouldn't you actually be serving at whatever PSI is appropriate for the beer type + carbonation level + temperature. To maintain proper carbonation?

Though that seems it would be a pain.

 
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Old 05-31-2012, 03:23 AM   #2
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Serving pressure is dependent on beer line length pressure and temperature.

You are not going to "ruin" a beer by serving at a different pressure (perhaps with the exception of a Belgian style). You will be serving an under or over carbed beer.

12 PSI is a round about number, to serve beer at the proper temp, then you have to balance it.
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Old 05-31-2012, 03:29 AM   #3
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Maybe this chart will help... At 45F, 12PSI gives you below 2.4 CO2 volumes.

I use that chart to figure out the psi (at serving temperature) to place kegs at to hit the CO2 volumes I desire. I have a dual body regulator, with bulkheads feeding into the brew fridge, with two manifolds inside, feeding any of the four kegs within. So, I can have my brown ales at a lower pressure set than my pale ales. Makes for much better homebrew enjoyment..
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Old 05-31-2012, 05:14 AM   #4
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Quote:
Originally Posted by EliW View Post
So I guess I'm saying, should you really be serving at 12 PSI? Because won't that affect over time the remaining beer? Shouldn't you actually be serving at whatever PSI is appropriate for the beer type + carbonation level + temperature. To maintain proper carbonation?
Yes, you absolutely should serve your beer at whatever pressure equates to your desired carbonation level at your serving temp. If you just serve at 12 psi, the beer will eventually end up carbed to whatever level equates with 12 psi at your temp. After finding your required serving pressure, you should then make your beer lines long enough to create a balanced system at that pressure. I think the 12 psi number is used a lot, because it's such a common serving pressure. I keep my beer at 40F and like about 2.4 vol of carbonation for most of my beers, which requires a serving pressure of 11 psi. Depending on your serving temp and desired carb level, you may need a higher or lower serving pressure. You mentioned 2.4 vol and 45, which would require a serving pressure of ~13.5 psi.

For taking kegs to parties, the serving pressure isn't all that important. It takes a few days at a different pressure to have a significant impact on the carbonation level, so for a 5-10 hr long party and unknown serving temp, just set it to whatever gives you a good pour.
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Old 05-31-2012, 01:40 PM   #5
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So, from what JuanMoore is saying ... yes, it does mess with your carbonation over time.

Granted if you take a keg to a party and it's drank within 5 hours, no issue.

But I was more thinking about situations such as:

* Taking a keg to a party, it's only half-drunk, it's temperature has changed a lot over the course of time. Then needing to deal with trying to recarb it appropriately if it's changed, when you bring it back home and have it sitting in the basement for a few weeks.

* Taking multiple kegs to a 2 week long camping event, where you may tap one of them and it stay tapped for a week before it's kicked.

* Putting a keg in your kegerator and letting it live for weeks/months.

In the end, it sounds like your best bet is either to:
* Not worry about it too much
or
* Carb everything at the same level (the 11 or 12 or whatever and live with that)
or
* Plan on quick carbing everything, getting good at that, and at 'fixing' the carb when it changes.

:-/

 
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Old 05-31-2012, 01:56 PM   #6
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Quote:
Originally Posted by Golddiggie View Post
Maybe this chart will help... At 45F, 12PSI gives you below 2.4 CO2 volumes.
Any idea how to print that to fit a full landscape page and in the original color? I printed it and it's barely readable on paper.
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Old 05-31-2012, 03:04 PM   #7
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Quote:
Originally Posted by Revvy View Post
Any idea how to print that to fit a full landscape page and in the original color? I printed it and it's barely readable on paper.
Select 'Print Preview' from your browser and scale it to fill your output page size. You can adjust the orientation there too. Pretty easy thing to do.
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Old 05-31-2012, 04:02 PM   #8
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"* Putting a keg in your kegerator and letting it live for weeks/months."

That one is the outlier.

Assuming you kept the CO2 connected to the keg and set to whatever gas pressure that - once the beer reached equilibrium - provided satisfactory results, whether you're drawing pints or not you could leave it like that for years and the carbonation level will not change...

Cheers!

 
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Old 05-31-2012, 09:46 PM   #9
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Quote:
Originally Posted by EliW View Post
Granted if you take a keg to a party and it's drank within 5 hours, no issue.

* Taking a keg to a party, it's only half-drunk, it's temperature has changed a lot over the course of time. Then needing to deal with trying to recarb it appropriately if it's changed, when you bring it back home and have it sitting in the basement for a few weeks.
Disconnect the gas when the party is over, and then reconnect the gas at serving pressure once you have it back home and at serving temp. The carbonation will have barely changed, if at all, and will come back to equilibrium quickly after being back at your desired temp and pressure. It's not really any different from the situation where the whole keg is consumed in 5 hrs. You do realize that if you disconnect the gas and liquid lines, and then change the temperature of the beer, the carbonation will stay the same right? It's the pressure in the headspace that will change.

Quote:
Originally Posted by EliW View Post
* Taking multiple kegs to a 2 week long camping event, where you may tap one of them and it stay tapped for a week before it's kicked.
Seriously? Either live with slightly variable carbonation levels (you are camping after all), or figure out a way to monitor and control temps accurately.

Quote:
Originally Posted by EliW View Post
* Putting a keg in your kegerator and letting it live for weeks/months.
What's the issue there? Set the serving pressure to whatever corresponds to your desired carbonation level at your serving temp, and leave it there. For most people that's between 9 and 14 psi. If you want different beers carbed to different levels, you need to buy a secondary regulator for each additional pressure you'll need.
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Old 06-01-2012, 01:43 AM   #10
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Remember that the keg is on the gas all the time. When you pour a beer, the co2 comes into the keg to replace the headspace that is left by the lowering of the beer. That means it remains at equilibrium. If you change the pressure (lower or higher) that does mean that the carb level will change, eventually, as a new equilibrium is reached.

Most of us don't have a "serving pressure" and a "carbonation pressure". My kegerator is at 12 psi, all the time. If I take a keg somewhere, even if it's warmer or colder, it's ok at 12 psi during that time. Then I bring it back and put it back on the kegerator at 12 psi.

The short answer is that yes, the carbonation level will change IF you change the factors that go into carbonation. But if you don't change anything, and just serve beer at the same pressure and temperature, it will remain exactly the same until the beer is gone.
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