Nitro carbonation vs serving pressure

[Bullhog]

I can't find a good answer to this question even though I know it's been asked in many different ways 1000s of times. So here I go. If I have a stout that I want to be carbonated to 1.8 vols, the pressure to carbonate the beer with 25% CO2 beer gas is still much lower than the desired serving pressure in the 34-40f degree range (which is on the cold side, how I want it). Setting the PSI to 35-40 for proper nitro faucet pours would overcarbonate the beer, resulting in foam. So where is the balance? Are you all setting your psi higher right before serving and then setting it back down, or are you slightly overcarbonating and setting the serving psi too low out of the nitro faucet range so no adjustments are needed at serving time? It seems to me that if you want to have your psi set to 35 and you want 1.8 vols, the answer is a kegerator temp of 50f, which I do not want to set mine to.

I should add that I really want to set my kegerator to 34f so I can lager in it, and I would prefer my serving pressures not to overcarbonate my beers. I also prefer the beer extra cold as it warms up quickly where I live. Maybe I'm just putting too many restrictions on myself, and compromise is needed, but I can't be alone here.

Has anyone tried carbonating with pure c02 and then using pure nitrogen to dispense? I am not sure why I haven't heard of doing this; if you can buy beer gas, I imagine you could buy pure nitrogen.

 

[fluketamer]

you can but boyles law or henrys law or some old really smart guy prolly with a beard determined that the partial pressure of gasses will cause the beer to continually go flat. you can get around this by constantly reinjecting co2 into the stout but its a juggling game. i know because i have done it using mini nitro carts to dispense portable nitro stout. its definatley not ideal and i wouldnt do it long term.


below are some threads with the method i have used.

https://www.homebrewtalk.com/threads/50-off-nitro-miniregulator.730359/

https://www.homebrewtalk.com/thread...rving-with-100-nitrogen.729339/#post-10331474

https://www.homebrewtalk.com/threads/little-nitrogen-cartridges.728285/#post-10285234

 

[day_trippr]

If this stout is to be dispensed through an actual stout faucet at the typical 30-35 PSI recommended by most manufacturers the OP might want to rethink the "1.8 volume" thing because that high a CO2 content will cause a foam-fest at the faucet.

I carbonate my imperial chocolate stout to just 1.2 volumes of CO2 which when dispensed at 35 psi through my Taprite stout faucet (which is actually produced by Krome Dispense, fwiw) results in a nicely cascading pour. I usually use 70/30 beer gas which works out well with the 36°F temperature of my keezer to maintain that carbonation level. 1.4 volumes of carbonation is the practical limit before foam becomes a real problem...

Cheers!

 

[Bullhog]

I carbonate my imperial chocolate stout to just 1.2 volumes of CO2 which when dispensed at 35 psi through my Taprite stout faucet (which is actually produced by Krome Dispense, fwiw) results in a nicely cascading pour.

So here's the big question: do you always keep the pressure on your keg at 35 psi, or do you turn it way down so it doesn't over-carbonate? If I'm doing the math correctly, 35 psi of 30%co2 would put your carbonation at 2.5 vols @36f

I'm worried about over-carbonating, but you seem not to have a problem with what is essentially my same situation. What's your secret? Do you just turn the gas off and not worry about the PSI when you're not serving?

 

[fluketamer]

i assumed the 35 psi of 70/30 doesnt overcarbonate your beer. unlike pure co2 at 35 psi which i think would overcarbonate the beer.
but i am just assuming.

 

[day_trippr]

I never shut gas off to anything on tap. Ever.

Fortunately, your math is not correct as it isn't considering absolute pressure but instead is using gauge pressure. Here is an explainer thread with a contribution from our resident physics guru @doug293cz where he includes a spreadsheet that works for beer gas blends:

https://www.homebrewtalk.com/threads/switching-from-a-co2-to-nitro-mix.723446/#post-10194503

Cheers!

 

[Bullhog]

i assumed the 35 psi of 70/30 doesnt overcarbonate your beer. unlike pure co2 at 35 psi which i think would overcarbonate the beer.
but i am just assuming.

My assumption is that you multiply the pure CO2 psi by the reciprocal of the percentage of the % co2 your beer gas is. So for example if you want 2.1 vols of co2 and you are using 30% co2 beer gas and your kegerator is at 36f: beersmith calculates 6.15 psi needed. multiple 6.16 x (1/0.30) = 20.53 psi. So, again this is just my assumption, if you keep your beer gas at 20.5, you would get around 2.1 vols of co2 at 36f. Doing the same math backwards, if you want to set your serving pressure to 35 then you need to guess and check with a calculator in order to achieve 35*0.3 = 10.5 psi of pure co2. In this made up situation, 10.5 psi would give you 2.527vols co2 if using 30/70 beer gas at 36f.

Edit: well, just ignore all of this, as I am wrong. Happly wrong as well.

 

[Bullhog]

I never shut gas off to anything on tap. Ever.

Fortunately, your math is not correct as it isn't considering absolute pressure but instead is using gauge pressure. Here is an explainer thread with a contribution from our resident physics guru @doug293cz where he includes a spreadsheet that works for beer gas blends:

https://www.homebrewtalk.com/threads/switching-from-a-co2-to-nitro-mix.723446/#post-10194503

Cheers!

This is FANTASTIC. It tells me that if I set my kegerator at 36f (which I do) and I want 1.3 vols CO2, then I should set the gauge pressure to 37.3! I love it! I just hope it's correct!

 

[day_trippr]

You can trust @doug293cz

 

[Bobby_M]

I get a great nitro pour at 30psi on 75/25.

 

[Closet Fermenter]

I get a great nitro pour at 30psi on 75/25.

Tell me about your beer line, please. I just purchased some eva barrier hose (from you!), but unsure what length I should be using here. I have the 75/25 mix.

 

[Bobby_M]

The length on a nitro faucet supply is almost irrelevant because the restriction plate in the nozzle does a lot more than the line does.