I've been reading a lot lately about kegerators, keezers, and long run beer dispensing researching options for my setup. (There are a lot of great discussions in this group.) I ran across this vendors explanation, with diagrams, and thought it worth sharing. I searched for the definitive thread on the subject so I could post it there, but in not finding one decided to create a new thread.
The link to the original page is: http://www.rapidswholesale.com/resources/beer_guide4.shtml
The vendor has many pages of product descriptions (beer pumps, trunk lines, glycol chillers, forced air systems) that are full of info for anyone considering these options. And no, I have no affiliation with this or any other vendor, I just find online catalogs such as this to be a great resource.
My conclusion: Glycol looks pretty doable and affordable (for runs over 25 feet) with the exception of that damn chiller - they are expensive. Home built/cobbled together chiller solutions might make the cost feasible. The forced air solution (for runs under 25 feet) is pretty affordable.
Happy reading. Cheers.
Long draw beer delivery systems are designed for high volume beer dispensing. Long draw systems rely on a walk-in cooler to store tapped kegs of beer, long beer lines of greater than 5 feet, and a means of keeping the beer cold between the walk-in and the dispensing point.
There are two common types of long draw systems:
Air shaft Requires two ducts, the first style carries fan forced cold air and the beer lines as they leave the walk-in cooler up to the beer tower. The second duct is for the return air flow back to the walk-in cooler. In the second style, the ducts are nested and the interior duct contains the multiple beer lines and fan forced cold air from the cooler to the tower. The exterior duct carries the outflow cold air back to the cooler. Either ducting method is insulated with ½ to 1 insulating foam tubes.
Air shaft systems are very easy to install and maintain, but are limited to run lengths of 25 feet or less. In addition, curves and bends in the run of the ducting must be kept to a minimum. Curves and bends cause turbulence in the cold air delivery and suffocate the air flow.
Glycol Chilled System Glycol is non-evaporating refrigeration liquid. Its properties allow it to achieve cold temperatures without freezing. In a glycol system the multiple beer lines are combined side by side with glycol lines which are in turn bundled inside of an insulating foam rubber tube. The assembly of lines and insulated tube is referred to as a trunk line (illustration C above). Each beer line must be in contact with one of the glycol lines. Because of this need for constant contact multiple glycol lines will be needed for trunk lines with more than six beer lines in them.
By chilling the liquid glycol and pumping it into lines that run alongside the beer lines, the beer is maintained within one degree of the temperature in the walk-in cooler. It is important to note that the glycol lines themselves cant chill the beer! They simply help maintain the temperature of the beer on its trip from the walk-in cooler to the faucet.
Both air cooled and glycol cooled systems need the same mechanics to move the beer from the walk-in cooler to the faucet. The kegs must be pressurized to force the beer through the lines to the faucets. There are three ways to move the beer through the lines: straight CO2 pressure, mixed gas pressure, and beer pumps.
Straight CO2 is the most common method of pushing the beer through the lines. It is cost effective and easy to understand. A bulk CO2 tank is connected to the keg through a coupler, the keg is pressurized and the beer moves up through the beer line.
As easy of a concept as CO2 pressurization is, there are many factors that have to be accounted for. The very beer lines themselves add resistance to the beers movement, and that resistance grows as the lines get longer. As beer lines get longer, CO2 pressure at the keg would have to be increased.
As with anything else that must be physically moved, gravity comes into play. If the beer is to be moved vertically, more force is required to push it as compared to a level line of travel. The steeper and longer the line run, the more force must be exerted to move the beer upward - about 1/2 pound of pressure per foot of rise. Conversely, every foot of drop in the elevation of the line run would require deducting the same ½ pound of pressure.
Surprisingly, beer is actually quite tender. Beer is sensitive to temperature, pressure, over exposure to air or other gases, changes in restriction and simply age. If any one of these factors is out of balance, the taste and appearance of the dispensed beer can be severely affected.
For a long draw beer system, we have already discussed temperature changes. Both the air cooled and glycol cooled systems help in this area. But as the CO2 gas pressure is increased to move the beer through very long or steep lines, the beer will become over carbonated. Sometimes, mixing CO2 with a gas that doesnt interact with the beer can help with over carbonation. The most common gases to use are nitrogen and air.
CO2 and air mixed gas systems are the least expensive, but they are normally found in only the most high volume businesses. The CO2 / Air mixture cannot be in contact with beer for long before the beer goes flat and oxidizes. (There are some clubs that use air only to pressurize their systems. But a keg tends to be on tap for only an hour before it is empty and needs to be changed out. Even at this brisk pace the last beer may not be as good as the first due to oxidation and the beer losing carbonation in contact with the air).
A solution is to use an inert gas that doesnt interact with either the CO2 or the beer. Nitrogen is the gas most commonly used. A system using nitrogen as the mixer gas with CO2 diminishes the chances of both over carbonation and oxidation. The down side is that nitrogen must be purchased in bulk tanks and delivered by the gas vendor.
(It should be noted that certain stout beers require the use of nitrogen as a mixing gas.)
Increasingly, beer pumps are being used to overcome the downside of using mixed gases. A beer pump is a mechanical device that uses CO2 pressure to power a diaphragm that in turn moves the beer through the lines. CO2 is still used to pressurize the kegs to around 12 to 15 pounds, and CO2 powers the pump. However, the CO2 used as pump power never contacts the beer. Using a beer pump allows using as much pressure as needed to move beer upward or through long lines without the risk of over carbonation or the expense of a mixing gas and gas blender. One beer pump is required for each beer line within the trunk line.
Preventing waste with blown keg detectors.
Blowing a keg, which means unknowingly running a beer keg empty and allowing CO2 to fill the beer lines, is a problem with long draw systems. When there is no more beer to dispense from a keg, gas is allowed into the beer lines. An emptied beer line must have the gas eliminated from it, and refilled with beer (referred to as repacking the lines). This can be time consuming and wasteful of product even worse if it happens at a peak serving time. The trick is catching a keg after it empties and before the CO2 gets into the beer line.
Several devices are available to help prevent gas entry into the beer lines. All of them share the same principal of detecting gas as soon as it exits from the keg, and then shutting down dispensing. After replacing the now empty keg, a small amount of trapped CO2 is bled off and the line is ready to use and in service.
WHERE TO START?
The first question to answer is: How much distance is there between the walk-in cooler and the faucet on the beer tower?
If this distance is greater than 25 feet, a glycol system should be used. Less than 25 feet decide between a glycol system and an air cooled system.
Next, decide on the number of beer faucets that will be used. This will help determine how many beer lines will be in each of the trunk lines.
Decide how many beer towers are to be installed, the number of faucets on each tower and their locations on the bar or bars. If there are multiple tower locations on a bar, note the distance between them.
Please note that a glycol system that supplies multiple bars or towers may need additional glycol pumps added to the chiller. Large venues may require multiple glycol chillers and walk-in coolers.
Describe in writing the run for each trunk line (glycol OR air cooled). An example would be: Rise five feet from the keg to the ceiling, runs 25 feet horizontally, and rises 8 feet to the bar, runs three feet horizontally, and rises 2 feet to the tower faucet. This will help determine both the trunk line length and the beer line diameter. Ten feet should be added to each trunk line measurement for installation waste. Please be aware that trunk line can only bend as tight as a 30 radius curve.
Make a decision between CO2, mixed gas or beer pump pressure for the beer system depending on line lengths and amount of lift required to reach the dispensing point.