Serving vs. Carbing Pressure

dan_s · January 29, 2014, 10:43pm

Hello Everyone,

I’m still working my way toward understanding the basics of balancing my new keg set up and am wondering if anyone can help me with the following concept:

As it happens, I currently have a dual body regulator set up in my keezer, with the temperature set at 42*, and am serving from picnic taps.

For the sake of argument, lets say I’ve just brewed a Saison and a Dry Stout. When kegging time rolls around, I look online at one of the many force carbonating calculators that are available and use the “set it and forget it” method to carbonate my beers as follows:

Saison (3 vols. CO2) - force carbed @ 19 PSI

Dry Stout (1.5 vols. of CO2) - force carbed @ 2 PSI

Two weeks pass, and now that my beers are fully carbonated, I set the pressure to dispensing levels. We’ll say I get a nice pour at 11 PSI.

My questions are these:

If I leave the pressure set at 11 PSI for the 2 months or so it takes me to empty a keg, would the carbonation level of each beer remain constant or would the Saison gradually become less carbonated and the Stout gradually become more carbonated?
If the carbonation levels would change, how would I adjust the pressure of each beer to maintain my desired level of carbonation without mucking up my pour?

In retrospect, this post reads a lot like a word problem from high school – sorry if it brings back any bad memories!

loopie_beer · January 29, 2014, 11:52pm

[quote=“Dan S”]Hello Everyone,

I’m still working my way toward understanding the basics of balancing my new keg set up and am wondering if anyone can help me with the following concept:

As it happens, I currently have a dual body regulator set up in my keezer, with the temperature set at 42*, and am serving from picnic taps.

For the sake of argument, lets say I’ve just brewed a Saison and a Dry Stout. When kegging time rolls around, I look online at one of the many force carbonating calculators that are available and use the “set it and forget it” method to carbonate my beers as follows:

Saison (3 vols. CO2) - force carbed @ 19 PSI

Dry Stout (1.5 vols. of CO2) - force carbed @ 2 PSI

Two weeks pass, and now that my beers are fully carbonated, I set the pressure to dispensing levels. We’ll say I get a nice pour at 11 PSI.

My questions are these:

If I leave the pressure set at 11 PSI for the 2 months or so it takes me to empty a keg, would the carbonation level of each beer remain constant or would the Saison gradually become less carbonated and the Stout gradually become more carbonated?
Yes this is exactly what will happen.
If the carbonation levels would change, how would I adjust the pressure of each beer to maintain my desired level of carbonation without mucking up my pour?
You are over thinking this. The nice thing about the set it and forget it method is that those ARE your serving pressures.

In retrospect, this post reads a lot like a word problem from high school – sorry if it brings back any bad memories![/quote]

itspossible · January 29, 2014, 11:54pm

No its simpler than you imagine.

A. To carb/ serv you use the same pressures at all times and then adjust your line length. Then the keg always remains at the same volumes until kicked and your pour always remains the same.
So I have one line/tap at/around 10-12 ft for kegs at 3+ volumes and the other lines set at 8 feet for kegs around 2.2-2.7. If not adjusting length to setting then you have to munkey around with pressures too much +/- to avoid foamy pours.

Also make certain you know where the fridge/freezer and beer in the keg is regarding temp. If you want to be able to gauge volumes/ pours correctly down the line.
IE: You can set the controller at 42f and the actual temp inside is -/+ 10f depending on age/ type/setting of the unit. So for example I have my kegging fridge (not freezer) turned up to the highest setting and the controller is set at 30f, The inside temp at the front of the unit is constant 37f and the rear is 35f. The beer inside the kegs is on average 1f higher. So my front two kegs sit at 38f and the rear two kegs sit at 36f. So I set gas accordingly.

dan_s · January 30, 2014, 4:28pm

Thank you both! I was hoping the answer was along those lines, otherwise I was worried I’d be really confused. So it appears that the missing variable in my equation is the line length (I’m currently using 5 foot lines). Am I correct that 3/8" ID tubing is the standard?

ITs, I like your idea of having varying line lengths on hand for different levels of carbonation and will look into experimenting with this myself. Can you (or anyone) recommend a source for buying in bulk? Also, is any one brand considered better than others?

itspossible · January 30, 2014, 5:32pm

No, 3/16ths is most commonly employed for short draw systems as it is narrow ID but thick sidewall.

http://home-brewing.northernbrewer.com/ ... &view=grid

Many still commonly quote 5 feet as being optimal which is typically far from correct.
I find as stated I need around 8-9 feet for common volumes around 2.5

When I first used 5 feet as recommended it was a foamy mess and I thought I was doing something else wrong, until I learned to do the balancing equation for myself and found it gave me around 9ft. So I recommend if not doing the equation just start with 10ft and cut back a half foot at a time until the pour is correct.

If the line is longer than it needs to be, all that will happen is the pour slows way down. Whereas if too short it will never be right.

These guys have it for around $0.53 a foot.

http://www.micromatic.com/draft-keg-bee ... C1200.html

I like the company I list below for cheaper parts sometimes and they are pretty knowledgeable regarding draft. Although I see their line is $0.68 which is even higher than our host at $0.63 for 30 foot.
Chi co has always met or excelled over others pricing in the past so it couldn’t hurt to call both Chi co and NB and ask if they will match or beat 53 cents a foot on a 100’ roll. Compare shipping amongst them also, it could be way better at one or the other depending on proximity to your location. Or you can pickup at NB if your close to the metro. They may have an extra on hand but they might have to order one from the warehouse, call NB customer service and if they agree to a pricing, they can also tell you if one of the stores has it in inventory or not.

This might be a way to change out lines quickly/ economically if you don’t have enough taps to have a dedicated higher volume line.

http://www.chicompany.net/index.php?mai ... cts_id=926

I currently have perlick “brand” line but ave used bevflex and others and they all have been fine.

loopie_beer · January 30, 2014, 11:49pm

Its brings up some good points. Start with 10’ that way you can cut off a few inches at a time to dial it in, if needed. BE CAREFUL. You can always subtract but not add to the line.

itspossible · January 31, 2014, 12:40am

Actually I kinda like those quick connectors I posted although when I think about them I dont think they would be suited for this task maybe other processes. As I think something within either the male/ female connector or both would cause gas to break out as it flowed through the connectors, which would cause a foam issue also.

What I currently use just for sake of easily cleaning the liquid system, but you could have a higher pressure hose ready to swap in for cheap are the following components.

A. Two swivel nuts/barbs on each line $0.50-$2.00 depending on retailer.

http://home-brewing.northernbrewer.com/ ... &view=grid

[attachment=2]swivel nut.jpeg[/attachment]
So each line looks like this:
[attachment=1]line-swivel.JPG[/attachment]

Then one of these MFL liquid keg disconnects. $5-8

http://home-brewing.northernbrewer.com/ ... &view=grid

[attachment=0]liquid.jpeg[/attachment]

itspossible · January 31, 2014, 12:43am

Then connected to the shank/tap by a MFL tailpiece. $5-8

http://home-brewing.northernbrewer.com/ ... &view=grid

[attachment=0]tail piece.jpeg[/attachment]

dan_s · January 31, 2014, 2:21am

Thanks again to both of you for setting me straight! Thanks also for the links, ITs – they were very helpful.

loopie_beer · January 31, 2014, 3:04am

That is exactly what I use. It makes switching from a ball lock to pin lock to a commercial keg a cinch.

itspossible · January 31, 2014, 6:18am

You bet, I have those tail pieces on my sankey disconnects, swivels on coldplate line, gas…everything as cleaning and setup is a breeze then no clamping / cutting tubing/ having hot water close etc…

BTW, You will find that even with 1/4" barbs it is hard to get 3/16" line onto them due to the thick sidewall which makes it very rigid, so simply heat up a small pan of water to boiling and dunk the end of the line for 30-60 seconds and it will slide onto the barb just like butter.