From
Micro-Matic Advanced Draft Training:- Temperature is the 1st determining factor for everything else in a draught system.
- For every degree above 380F, the internal keg pressure increases 1/2 lb as the CO2 expands.
- 380F is the most stable temperature for CO2
- At 380F, most kegged beer requires 12-14 lbs. of internal keg pressure in order to keep the CO2 balanced within the beer.
- With very short lines it's gonna be difficult to get enough restriction applied to the keg while also keeping your flow rate low enough that beer doesn't come flying out of your faucet... resulting in a ton of foam
- The ideal flow rate should be 2 oz's/ sec. The best way to test this is to hook up a cleaner pot full of water to your system and pour into measuring pitcher. i.e. start stopwatch as soon as you open the valve and stop at 15. You should have 30 oz.'s of water in your pitcher.
- To adjust the flow rate while keeping the keg pressure ideal, you can utilize different diameter tubing. Tubing diameter is measured by the "I.D." (interior diameter). I'm assuming you'll be using Vinyl so I'll list the restriction measurements for each size.
- 3/16" - 3 lbs/ft
- 1/4" - 0.85 lbs/ft
- 5/16" - 0.40 lbs/ft
- 3/8" - 0.20 lbs/ft
- 1/2" - 0.025 lbs/ft
To sum everything up in an easy way, if you use 3/8" hose with a length of 6', you won't have a problem giving your beer the CO
2 it requires while still providing enough restriction to keep your flow rate to 2 oz's/ sec. Since 3/8" hose is so standard you'll never have to retro-fit anything to your system.
Oh yeah! Most people use strait CO
2 in their systems - which is perfect... as long as you're running through more than a keg per week - however, CO
2 will start to dissolve into the beer after about 3 days, resulting in added carbonation and eventually your beer becoming pure foam. If you keep your beer longer than this, you'll want to use a "mixed-gas" blend, which is normally CO
2 mixed with N
2 which will allow you to maintain the proper applied pressure while reducing the likeliness that you'll over-carbonate your beer.