The most prevalent issue surrounding home kegerators today is how to get them dialed in to get consistently good pours from start to finish.
Solving this problem requires a practical understanding of how carbonated beverages work in a dispensing system. Beer is not like water - it pushes back where non carbonated liquids will simply flow with gravity or the push of air and other gases. To understand how this push operates you should understand beer's carbonation level and the carbonation's relationship to temperature. You can then begin to understand how to calculate CO2 push, preferred beer line length and the proper serving temperature for each style of beer you plan to dispense from your kegerator.
If the temperature and/or CO2 push of the beer in your draft system is only a little bit off it can greatly affect not only the carbonation level of the beer, but also the beer's taste. The first thing to understand is that each beer type has a certain temperature that it should be served at and a certain pressure that the beer should be dispensed with while at that temperature. If the temperature changes even two degrees Fahrenheit it can cause the beer to taste either flat or cause over foaming.
Volumes of CO2
|0 - 1.40||Under-Carbonated|
|1.50 - 2.20||Stouts and porters|
|2.20 - 2.60||Lagers, Ales, Ambers, most beers|
|2.60 - 4.0||Highly carbonated ales, Lambics, Wheat beers|
|4.1+||Over-carbonated (except for certain specialty ales)|
This is because beer is a solution of gas and liquid. The saturation point of beer changes dramatically with temperature. If you are a home brewer then you know that it is easier to add malt syrup to a hot boiling wort than to mix it into a solution with cool or even warm water. With CO2 it is different - the opposite relationship to temperature is true. The lower the temperature of the beer the easier it is to infuse the beer with CO2 gas. As the temperature of the beer goes up the saturation level goes down. This causes the CO2 gas to be forced out of the beer and that is one of the causes of over foaming beer served out of a home draft system.
If you want to get the most out of your home draft system and the beer dispensed by it, you should know the ideal serving temperature and CO2 or beer gas push specified by the brewery that produces it. Try to match the conditions specified even if it goes against your notions of pressure and hydrodynamics.
Remember that the idea is to maintain the pressure specified at the temperature specified. Too little CO2 gas can be as much of a problem as too much CO2 gas. In the former case, by having too little pressure you are making room for the CO2 already trapped inside the beer-CO2 solution to escape. If you use too much pressure it can also cause the beer to over foam as a result of too much CO2 trying to force its way into the solution.
What if you are the brewery that made the beer, at home, and you have no idea what the ideal serving temperature and CO2 push should be?
There is a great book that can help home brewers to understand how this relationship of pressure and temperature interface with specific recipes for brewing. The book is entitled "Brewing Classic Styles" by Jamil Zainascheff and John J. Palmer. This book contains 80 well-crafted recipes for brewing beer that includes the volumes of CO2 that should be present in the beer. You can also reference our CO2 pressure chart online here.
Volumes of CO2 are the units that represent how much or how little the finished beer should be carbonated. Knowing this ratio you can determine the temperature and CO2 push required for serving the beer at the correct level of carbonation. There is also a nomograph at the end of the book which can show you how much priming sugar to use in a batch to attain the optimal carbonation level.
Optimal temperature is best determined by the type of beer and is more open to generalities. The Dialing in Your Home Draft Temperature article goes into greater detail about this subject, but here is a quick overview:
To a lot of home brewers the idea of pushing a beer at as high as 17 PSI seems like overkill, but remember that the beer pushes back. In order to maintain the proper level of carbonation a beer has to be pushed a certain amount. If the beer coming out of the other end of the beer line is flowing too fast this may be due to having too short a beer line on the other side. The length of beer line, rise and fall of gravity, type of beer line, and the flow restriction of hardware can all take away push on the other end of the flow of beer. This can be used to your advantage if you understand how flow restriction works.
Another factor in pouring the perfect pint is the glass. We have different types of beer glasses for a good reason. Certain beers just taste better when served in the appropriate glass. This is not to say that one type of glass works better than the other in all circumstances, but it is best to fit the proper glass with the proper beer and to keep your beer glasses chilled to the exact recommended serving temperature of the beer in question.
Related Kegerator Articles :
Co2 Air Tank Guide -- An overview of CO2 tanks and their functions..
Installing Co2 Lines Efficiently -- Get tips on installing CO2 lines.
Finding the Right C02 Regulator -- Read why regulators are an important part of the draft beer system.