Keg Carb Pressure Vs Serving Pressure

[fifis101]

I tried to find something on this but nothig quite answered my questions. I used the keg carb calculator to get the my keg pressure which turned out to be 0.45bar (6.5psi) but I seem to hear a lot that people use serving pressure of 12-14psi. So I was a little curious, is there a difference of is the carb pressure just the same as the serving pressure for that beer?

 

[duncbrewer]

THe carb pressure is to get the correct vols of CO2 into the beer for the style.

The serving pressure is a bit higher to compensate for moving the beer from A to B ( keg to glass via tap thru the pipes and valves and non return valves ).

If the pressure isn't high enough the beer goes flat.

 

[fifis101]

Do you mean the beer goes flat while being transferred through the serving line?

Using the line length calculator for the 6.5psi & 4mm beer line I only need like 2.5ft of line, which is fine for my kegerator. Does this mean I can just set my keg at 6.5psi & leave it?

Also if you carb at a lower pressure than the serving pressure, do you have to turn the pressure up just to serve and back down while the keg is sitting (say until next weekend)?

 

[duncbrewer]

No if the line length is right and the psi is correct as your calculations show then you can just leave it at that all the time.

You will get some changes as the keg empties ( due to the change in height ) and might find that the last of the keg is more foamy so you might want to turn it down. Because I have a non return ball lock gas connector on the keg and another non return valve on the gas in ( double protection ) and an inline pressure gauge and reducer my pressure is a bit higher than the pure chart reading suggests. Similarly if your kegs were above the taps then it all would need to be a bit lower pressure. But the line length calculator should take that into account.

You luckily don't need miles of tube with the 4mm internal diameter tube.

 

[fifis101]

Awesome. I thought it was most likely based on others having larger line diameters and non-returns etc but I had to make sure.

So why is it that people wrap up long length of beer line in their kegerators instead of just going down in diamater? Seeing as the calculator is based on pint pour time it can't be flow rate. Is there any other advantage of larger beer line diameter?

 

[duncbrewer]

Old habits die hard I suppose and the trade industry I think uses the larger tubes more often ( cellars a long way away ) also things like beer engines work on low pressure so large diameter tube helps the flow. Flow is related to the 4th power of diameter so if you double the diameter the flow in a tube can increase 16 times. Hence the advantage of narrow tubes in our short run situation.
Long tubes is more to clean / get infected and takes up more space. My keg fridge is a converted full height commercial fridge and so has 6 kegs on two levels some near the tap height and the rest below. Gets complicated but I've got it all balanced and even a stout on nitro was the latest challenge.
Setting up the beer engine is the current project, the most exciting yet !

 

[fifis101]

Yeah makes sense.
Sounds like you have quite a setup! The idea of a beer engine has always intrigued me. I can't say I have ever tried a beer from one before.

 

[duncbrewer]

You've got the climate for cask ale in Tasmania ( although you spell it Tasmanua ?). Really have to try cask ale and then it's uniqueness does shine through. Like many things it's a different product with it's pros and cons.
I only moved to the Keg fridge and taps in the last 6 months as I realised serving good beer badly was not doing it any favours. Wandering from keg to keg with a CO2 cylinder and a party tap on a kegland adjustable ball lock connector is not giving the product the best chance.

 

[fifis101]

I'll check out cask ale and thanks for the pick up on my misspelling of Tasmania haha!

 

[duncbrewer]

No problem thought I was outside a cultural loop when I saw it.

 

[kadmium]

Hey mate,

It can all get pretty complicated and Duncbrewer has given you some great information. My small addition is to say that 6.5psi may suit one particular style of beer but not others. For instance stout vs pilsner vs wit etc etc. Some you want more 'spritzy' and some you want less. This means you need more or less pressure in the keg to maintain that level of carbonation.

Essentially the liquid sits in the keg and the over pressure of the CO2 forces it into solution inside the liquid. But it wants to come out. So if you ramp the pressure up in the keg (say 10 for ease of use) to get the right 'fizz' but you need only 5 to serve, over time the fizz will go down as the gas comes out of the beer to maintain the 5psi level rather than from the bottle itself.

You also need to work out the temp that you serve the beer at which determines the level of pressure. I find many people over chill their beers (serving at say 1c) and find most beers benefit from serving at say 3 or 4c (unless you're doing real ales etc)

If you truly want to have multiple styles with multiple pressure levels, then your best bet is to get a gas manifold (one in valve with multiple out valves) with individual inline regulators on each line. This means the pressure in from the bottle could be say 20psi and then on each gas line going to a keg you can set them at the required pressures, say one at 11, one at 6.5 and one at 9 or what ever. This then leaves an issue with beer line length. The best bet would be to get a Flow control disconnect for the beer side. Some people go with a Flow Control Tap, however I do not find these to be great. I would suggest a Flow Control disconnect which lets you set the flow rate out of the keg, kind of like a regulator for beer flow.

This may cost you a little money in the short term but will provide ease of use and ability to individually control each keg. For instance, if you want to put fizzy water (soda) on a tap or a carbonated Rum and Coke etc, you need much higher pressure than the others and then have issues controlling the flow out of the taps.

Food for thought.

 

[duncbrewer]

@kadmium I haven't been that impressed with the flow control disconnect. Has been much better with the correct line length calculations.
I agree though I made my splitter out of duotight T pieces which works fine as opposed to the manifold ( couldn't get one at the time and had loads of T pieces ). I have the reg at 30 psi for the carbonated water and then an inline regulator reduces for the beers. I agree will need more regulators inline if I decide wheat beer or prosecco on tap.

It's a tricky question of balance, don't start a keg setup without a carbonation chart, pressure gauge and a thermometer and a tape measure I suppose. Plus as you say know the beer carbonation volume required or desired.

 

[kadmium]

@kadmium I haven't been that impressed with the flow control disconnect. Has been much better with the correct line length calculations.
I agree though I made my splitter out of duotight T pieces which works fine as opposed to the manifold ( couldn't get one at the time and had loads of T pieces ). I have the reg at 30 psi for the carbonated water and then an inline regulator reduces for the beers. I agree will need more regulators inline if I decide wheat beer or prosecco on tap.

It's a tricky question of balance, don't start a keg setup without a carbonation chart, pressure gauge and a thermometer and a tape measure I suppose. Plus as you say know the beer carbonation volume required or desired.

Yeah for sure man! And did you just say prosecco on tap? Why have you done this to me... my missus will be all over it during summer! GREAT IDEA!!!!

Off topic, but do you just buy bulk prosecco and then fill a keg? Or make your own?

 

[duncbrewer]

Well i followed the advice of someone on the american homebrew forum I'll look up the link and our chat. We were discussing wine on tap and then got onto prosecco.

Yes make my own. Have only just started a few wine kits recently and also made some Elderflower fizz that was brilliant. Can you get Elderflower in your Locale?

 

[duncbrewer]

Found the thread re the prosecco.

https://www.homebrewtalk.com/threads/new-to-kegging-100-co2-or-nitrogen-co2-mix.691214/#post-9085921
post 25 and on a bit.

I pressure fermented the Elderflower and think you could do the same with the prosecco.

 

[fifis101]

Thanks for all that great advice kadmium. None of what you have said is new to me, I was curious to why I kept reading people running higher pressures that I was. I am currently assembling my kegerator with a gas maniforld and inline regulators. I plan on having 4 kegs and I was thinking of setting up 4 beer lines at different lengths to suit different pressures (say 6, 8, 10 & 12 psi). That way I can just run the higher carbed beer on the longer length etc. That would get me in the ball park and my adjustable taps can do the remaining slight adjustment. Either that or just have a few extra lengths of beer line cut ready to go for different pressures.

 

[djebel]

If you are going to regularly change line lengths, set up your taps with a post on the back side. Then make up the different line lengths to suit with a QD on each end. When you need to swap one out, it's quick and easy to do.

 

[fifis101]

If you are going to regularly change line lengths, set up your taps with a post on the back side. Then make up the different line lengths to suit with a QD on each end. When you need to swap one out, it's quick and easy to do.

Exactly what I was thinking. I'll see how the 4 different lengths go for now as I've only just got enough beer line for that at the moment and no spare QD. If it becomes an issue those bits can go on the next KegLand order.

 

[fifis101]

Seeing as flow control was mentioned before with the flow control disconnects. Has anyone tried using the duotight ball valves as a flow control? I know they may make a bit of turbulence but if you have them at the keg end this may settle out by the time the beer makes it to the tap. Plus they are only $2.95!

 

[duncbrewer]

@fifis101
The side pull taps have a ball valve on the handle instead of the on off of the intertap. They then go into a stout type head with the little diffuser in it.
This allows you to pour different types of foam on your Czech lager. I am not enthused by this idea, I want less foam on my beer when I buy it in a pub.
But in answer to your question not sure about the effect of that ball valve in a system.