carbing at lower elevation

Thu Dec 26, 2013 2:36 pm

Hey guys I searched and found (and read ) one other topic on this subject, but it didnt help me with my specific situation.

Currently ive got a batch finishing up fermentation for a trip up to the mountains on the weekend of Jan 10th, 2014.
It should be done fermenting and ready to rack into the keg around January 4th.

Were traveling from an elevation of ~314 ft up to ~6732 ft.
I crosschecked some charts and it seems that the atmospheric PSI will go from about 14.7 PSI (@314 ft) to 11.3 PSI (@6732 ft). which is about a 3.4 PSI drop


My question is whether or not i should carb it for 4 or more days before traveling up? or should i just force carb it the day of, at the higher elevation?

Are there any pros or cons to either way?

Currently i dont have a way to chill my beer to less than 65* F , so I usually Force carb, and most of the time its hit or miss on whether or not it ends up over carbed. however, going up to a higher elevation, the temperature will be at or below 40*F so im sure i will have no issues carbing it up there....

I guess my real concern is whether, i will have issues with foam or over/undercarbonation, if i carb it slowly at a 65-70* at a lower elevation, compared to if i just waited and attempted to force carb it, at a colder temp and higher elevation?

Sorry if this topic is all screwy, im still a noob...particularly to keggin and carbing :P

Id appreciate any insights, experiences, or advice.

thanks!


-Syke
syke186
 
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Re: carbing at lower elevation

Thu Dec 26, 2013 4:20 pm

Not sure if it even much matters.
I'm curious. Why can't you cool your kegs?
When I got my kegs, I filled up a garbage can with snow and kept them in the basement.
Do you have more than one keg?
If so, chill one and let settle, then transfer to another keg.
Put the the gas on the desired level and put it in the trunk, hooked up.
It'll be perfectly carbed when you get to where you are going.
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snowcapt
 
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Re: carbing at lower elevation

Thu Dec 26, 2013 5:28 pm

Simple answer: Carb at home and take it to the mountains. For 2.5 volumes in the mountains set the regulator to 15.7 psi and use 5' of 3/16" tubing to serve the beer.

Long answer:
I'll have to make some assumptions but here is what I would do.
And let's make sure we're all using the same terminology.
atmospheric pressure = the pressure exerted by the weight of air above it (at sea level this equals the 14.7 psi you listed, while at 6732 ft there is less air above pushing down so the atmospheric pressure is only 11.3 psi). If I put an "a" after psi it means pounds per square foot vs atmospheric.
Gauge pressure = pressure referenced vs atmospheric pressure. a "g" after psi means this measurement is gauge pressure.
Absolute pressure = the pressure referenced against a vacuum. or atmospheric pressure + gauge pressure.

You never said exactly what level of carbonation you are going for so let's guess you are going for 2.5 volumes. If you want that level of carb at 65°F at home you would need to set your regulator to 28psi gauge (I'm gettting those pressures from http://www.kegerators.com/carbonation-table.php). Now you let it equilibrate over those 4 days then disconnect the C02 from the keg.
If you kept a pressure gauge on your keg and dropped the temperature from 65° to 40° you could watch the pressure drop from 28psi down to 12 psi. It's the same volume of CO2 in the keg but as it gets colder there is more space between the beer molecules so the CO2 can move in there easier and there is less pressure exerted.
Next if you had the keg at 40°F at sea level, properly carbonated at 2.5 volumes, the gauge would show 12 psig which means the absolute pressure is 12psig + 14.7 psia = 26.7 PSI absolute. . If that keg is then driven up 6732 feet into the mountains (and kept at 40°) the absolute pressure in the keg is still the same at 26.7 PSI. But now the ambient pressure is 3.4 psi less. So your gauge reads 15.4 psig (26.7psi-11.3psia). This is where you would want to set your regulator to maintain 2.5 volumes of CO2 at 6732' elevation at 40°F.
It doesn't really matter when the temp change occurs. So you can carb it at home at 65 at 28psig, then drive to the mountains and set the regulator at 15.4 and let the beer cool down to 40°F.
Now we need to look at your dispensing method. Ideally you want the beer to leave the tap gently at just a smidge over 0 psig.
The equation can get more complicated but if we assume you will hold the tap at the same level as the keg we can eliminate the elevation difference between the liquid into the tubing and out of it. Then we are left with just manipulating the length and size of the beer line. A 3/16" inner diameter tubing has a pressure drop of approximately 3 psi/foot. We simply take the pressure and divide by the pressure loss per foot to find the length of tubing required. 15.4psig(3psi/foot) gives 5.23' of 3/16" beer line.

Patterns
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Re: carbing at lower elevation

Thu Dec 26, 2013 5:32 pm

I don't think it'll matter much. Flat Tire is bottled at high elevation & sold at lower elevations. I've had it poured here (same as brewery) and in Michigan (almost a mile lower), it wasn't noticeably different. Same with the Bell's & New Glarus I brought back, which were bottled at lower elevation & opened up here. Been too long of a day to really think about it much more than that tonight. I'd say if you have it carbed up & move it, it shouldn't be a problem. As long as the keg is sealed there's nowhere for the gas to go.
Lee

"Show me on this doll where the internet hurt you."

"Every zoo is a petting zoo if you man the fuck up."

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Ozwald
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Re: carbing at lower elevation

Fri Dec 27, 2013 7:59 am

Guys,

thanks to all for your advice and insight. A big thanks to Patterns for that extremely detailed response!!

im a details kinda guy, and that was exactly the response i was hoping to get!
Im sure i could have just gone with general advice, but i like to know the intricacies of my craft (pun intended!! :aaron )
Unfortunately, my math and knowledge is not as good as yours! haha

Thanks again to all!

And if theres any more tips or tricks, please feel free to post.
I will continue to watch this thread, and im sure it will come in handy for others.

-Syke
syke186
 
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Re: carbing at lower elevation

Fri Dec 27, 2013 2:21 pm

Wow, I was tired. I never saw Patterns' post til now.

No worries, head over to the New Users section & introduce yourself so we can pencil you in on the hazing calendar.
Lee

"Show me on this doll where the internet hurt you."

"Every zoo is a petting zoo if you man the fuck up."

:bnarmy: BN Army // 13th Mountain Division :bnarmy:
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Ozwald
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