When thinking about draft beer systems, one of the key considerations is how to determine your kegerator gas pressure. To get it right, you'll need to have a carbonation chart and the recommended CO2 volumes from the brewer.
Using a carbonation chart
Let's say you start at 38 degrees for a beer with a requirement of 2.8 volumes of CO2. You will need to maintain this beer at 14 applied PSI in order to preserve the optimal carbonation level. However, you will also need pressure to push this beer out to the tap. If you are going to achieve this, you will need to consider the resistance of the system. Resistance in the draft system comes from the keg coupler, the shank and tap assembly, the beer line, the tap height in relation to the bottom of the keg, and even the altitude above sea level. A predetermined resistance value must be calculated for each of these components to learn the total resistance in the system.
Pressure applied inside the keg must also be sufficient to deliver the liquid to the tap. If the required pressure for carbonation maintenance matches the total system PSI resistance, the two are in equilibrium and the beer will be successfully poured without the character of the beer being affected. If this equilibrium isn't there, you need to take action to alter the system resistance or the beer will not pour properly, and the beer will become over- or under-carbonated.
Calculating system resistance
In a bar that has a high volume, it is commonly accepted to balance the system at a slightly higher push pressure without the beer being altered. If you're switching the kegs on a daily basis it is okay to work with a slightly heightened pressure because the beer in the keg won't have time to over-carbonate.
Pure carbon dioxide is usually the best beer gas option for pressurising your kegerator system. The only exception to this is with beers like Guinness which specify a requirement for a nitrogen/CO2 mix to enable high-pressure dispensing. At London Gases, we supply a wide range of gas canisters for your drink dispenser systems to help keep your taps running at their optimal level.