Question on Center Keg Height

Man oh man I know I am going to get raked over the coals for asking this one, but that's ok I can take it!


I would like someone to take a glance at the following formula and clearly define this: H = Total height from the center of the keg to faucet in feet
Yes, believe it or not, I am not completely clear on what the formule is looking for. Distance from top of the keg to the taps? The midpoint of the keg to the taps?
Feel free to poke a bit of fun at my ignorance, just make sure to provide advice after doing so!!

Calculating length of beer line

Once you have established the CO2 pressure on your keg, you can determine what length of beer line you need to balance the system. The basic premise is that we need to drop nearly all the pressure between the keg and the faucet, leaving 1 psi to actually get the beer to come out. The formula for calculating the line length is:

L = P - (H * .5) - 1
R

where

* L = length of beer line in feet
* P = pressure set on regulator gauge
* H = Total height from the center of the keg to faucet in feet
* R = Resistance of line from the following Resistance Table
* 1 = this is the residual pressure remaining at the faucet *

* If you need a higher dispensing pressure to increase the dispense rate, use 2 instead of 1.

This formula determines what line size & length to use to drop all but 1 psi of pressure, leaving just enough to dispense the beer.

Pretty sure it is half the height of the keg. The idea is that this gives you the average level of beer over the total draining of the keg, from full to empty.

And no, I'm not gonna make fun of you

Woudn't it be based on the bottom of the liquid dip tube in the keg? Much like a siphon...doesn't the liquid all "act" like it's all at the outlet level?


(Full confession -- I used the "middle-of-the-keg" idea when I did mine, but reading this thread got me to thinking...)

Bike N Brew said:

Woudn't it be based on the bottom of the liquid dip tube in the keg? Much like a siphon...doesn't the liquid all "act" like it's all at the outlet level?

Click to expand...

I always thought that a siphon was affected by difference in the height of the end of the hose and the level of the fluid being siphoned (not the level of the pickup opening)

As an example, when racking, moving the cane up and down in the carboy doesn't change the flow rate, but moving the carboy up or down or moving the end of tube does.

The 'end of tube' in this case is the beer faucet, and the fluid being moved is the level in the keg, not the dip tube depth.

Ahhh, you're right.

I said it "got me to thinking"...not necessarily thinking clearly

that formula is used to determine resistance needed in beer line to balance the system. It calls for the center of the keg itself to the faucet. To calculate, just take a tape measure from the faucet and let if fall straight down. eye ball where the center of the keg is and you have it. typically, if you are off by an inch or so it is not the end of the world. This equation helps to include the resistance of gravity along with the rsistance in the line.

This is not a stupid question by any means and there is no reason for anyone to "rake you over the coals" for asking. I spent 7 years in the draft business, and I saw tons of systems installed by "professionals" that were no where near balanced correctly.

One piece of advice, use the 1/4" line and calculate your length from there. larger lines are really for long draw systems, situations where there are multiple kegs hooked up in a series or setups where the faucet is very high mounted in relation to the keg.

keep in mind, this is not a siphon per sey, it is a pressurized means of dispensing. gas is "pushing" the beer not gravity siphoning it out. the equation calculates resistance and for it to work properly it needs to be calculated from the center of the keg

HAH!
Now I feel better about my question.
McSwiggin I currently have 5 feet of 3/16" beer line in my kegerator. I am going to replace it soon with 10 feet of foam free tubing in the near future.
I am going to recalculate my system tonight now that I know the true meaning of "center height".
Thanks guys.

3/16th should be a good size to use. I know a lot of people use 3/8, and that wuold require some extra length in the beer line. if your system is balanced, you won't really need "foam free" line. won't hurt though. If you are setting up a chest freezer conversion or a kegerator, 1/4" is the maximum diameter I recommend. Just be sure you use the chart that shows how to calculate resistance per foot on the i.d. of line you are using.

Anothe note to this. Some beers a very tempermental on balance of the lines. Temperature is also another key. As temp increases, you will need to adjust the length of your hose. if you keep a constant temp of around, say, 42 degrees or less, you should be fine. Some beers (like budweiser) will pour through a garden hose @ 48 degrees without foaming (obviously I am exaggerating).

The equation you have listed is pretty much the standard equation for most short draw systems. I am just stating that there are other fators at work as well.

3/16 beer line provides an average resistance of around the neighborhood of 2.2 lbs per foot. But there is also the resistance of gravity (thats why knowing the height to the faucet is important) and the faucet itself will provide a little resistance. If your faucet is 3 feet above the center of the keg (standard in a kegerator) 5 feet of 3/16 line should be good for a pressure of around 14lbs (or so I think, it's been a while). So, that being said, IF your faucet IS in fact 3 feet above the center of the keg, you actually need 4' of 3/16 beer line to balance the system at 12 psi (which is the magic # you should be trying to hit). Cutting a foot off would make it correct. If the internal temp of the keg is above 42 degrees, this can through all this math off. Most of these equations are designed for setting up a draft system to pour commercial beer (BMC). Your home brew will behave a little differently in that you may have different vols of Co2 carbing your keg, and Co2 is greatly affected by temperature. That being said, most homebrewers, that I know, usually balance there systems and carb thier beers in the same manner.

use this table to help with the adjustments depending on your height to faucet from center of keg:

http://kegman.net/balance.html

All this may help, or it may confuse you more, sorry for that. If it's any constellation, anti-foaming lines are nice, but can be avoided if proper balancing is present. Use commercial balancing theories as your guidelines and you should be O.K.

If you want to get into aligal (beermix) high pressure dispensing and nitrogen faucets, thats a whole other thread to get into.

Along the lines of carbing your kegs, you will find on this forum there are many different techniques. I have tried all with great success, but my favorite is still the set it and forget it method of force carbing for a couple weeks at 12psi. If you force carb at higher pressures, it may take a little trial and error. but you can always purge excess Co2 if needed, and it will work fine. Just keep in mind, if you have foaming problems, and your system is balanced, 99% of the time it is temperature that causes it (too warm).