Author Topic: Co2 Pressure/Temperature Question  (Read 538 times)

Offline liquidbrewing

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Co2 Pressure/Temperature Question
« on: December 28, 2010, 06:04:39 PM »
I recently tapped a new pale ale, and was surprised by the low carbonation. I normally always have good carbonation on my beers. I'm wondering if the cold weather is the culprit. My serving fridge is more or less outside, in an uninsulated garage. I know temperature affects atmospheric pressure, but is this the case?

Here's my normal carbonation schedule. Keg beer @ 30 psi for 48 hours. Turn to 12 psi for another 5 days. Seven days total. Then I usually turn to 5 psi for serving. Kinda the set and forget method. When the temperature drops, is this affecting the pressure at all?? I assumed that the regulator would be accurate at any temp. If there were changes in temperature, that's what the regulator is for, to keep the pressure where you have it dialed in.

If I'm not correct in my assumption, maybe I have a leak. Any thoughts?

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Offline oscarvan

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Re: Co2 Pressure/Temperature Question
« Reply #1 on: December 28, 2010, 06:42:26 PM »
Yes, temperature affects things greatly. What is the temperature in the fridge?
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Offline Mark G

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Re: Co2 Pressure/Temperature Question
« Reply #2 on: December 28, 2010, 06:51:26 PM »
I doubt the temp drop is the cause of your undercarbonation. If the pressure stays the same, and your beer temp drops, you'd get more carbonation, not less. The beer can hold more co2 at the lower temperatures. I'd guess your problem is that you're serving at 5 psi instead of the 12 psi you finished carbonating at. So eventually the beer will reach equilibrium at 5 psi, resulting in an undercarbed keg. Why not just serve at 12 psi and use longer lines to balance the system?
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Re: Co2 Pressure/Temperature Question
« Reply #3 on: December 29, 2010, 06:34:59 AM »
Yep, sounds like for some reason the beer did not get carbonated in the first 7 to 12psi and so you're actually carbonated at 5psi.

Looking at a Z&N chart
http://www.zahmnagel.com/LinkClick.aspx?fileticket=HuVGZ8tLaow%3d&tabid=77

If you're temp was say 35F at 12psi you'd have 2.73 volumes of CO2 and at 5psi you'd have 2.0. If your temp is more like 40F then it would be 2.5 vs 1.8.

It's important to balance your system so your desired level of carbonation is consistent. Dropping the pressure to dispense means your beer is becoming less and less carbonated over time.
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Offline liquidbrewing

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Re: Co2 Pressure/Temperature Question
« Reply #4 on: December 29, 2010, 09:16:26 AM »
I was actually talking about the temperature of my co2 tank.  If the drop in temp would affect any of the gauges on my regulator.  Basically the temp in my garage is the same in the fridge, sometimes colder at night.  Yeah and I'm in Florida!  We got down to 25 degrees Sunday night.

However, I understand now that dispensing at a lower pressure will eventually equalize the keg pressure, so in response to one of the posters above, I cranked it back up to 12 psi, poured a sample this morning and looks very nice!  The reason I was pouring at such a low pressure is because in the summertime here, it's like 100 degrees in my garage and since the Perlick faucets keep a small amount of beer outside the fridge, foaming over is a major issue for me.  But now I'll leave it at 10-12psi for serving and deal with it.

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Re: Co2 Pressure/Temperature Question
« Reply #5 on: December 29, 2010, 09:54:18 AM »
The tank pressure will lower as CO2 in the tank headspace goes back to liquid with the temp drop, but the line pressure will remain constant since it is gas...
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