Be absolutely certain of the temperature of the beer at the keg. Calibrate your thermometer in ice water to ensure it is reading 32 F. Try to target 38 F. Optimum flavor and product carbonation is most stable at this temp. Since your keg cooler is in the basement, hopefully it is not being used for food storage. Also, air cooled systems are notorious for temp. issues. Temperature fluctuations will substantially reduce your success with 100% CO2. Such as your timer. CO2 will work only if you can guarantee the same temp. 24/7/365 at the keg and all the way to the faucet. Otherwise, due to the laws of gasses and equilibrium, you will either impart gas into the beer or allow gas to leave the product prematurely. Both situations cause waste.
To compensate for these fluctuations in temperature, use a
gas blender at 60% CO2 / 40% Nitrogen at 22 PSIG to the kegs. Based on your existing set up, rebuild the lines from the wall bracket / trunk line with 10' of 5'16" I.D. barrier tubing and 5' 3/16" vinyl choker line. Not only will the higher pressure with this blend compensate for temp. issues, the carbonation level of the products will be the same the first glass to the last from the keg.
You may feel that you cannot afford the blender at this time. With your existing problems, you cannot afford not to. Do not get caught up with the use of cylinder gas at 25% CO2 / 75% Nitrogen. Yes it will allow you to use higher pressure but also will allow the beer to go flat. The only issue you need to worry about is your glassware. Keep it clean with chemicals designed for beer glasses.
Scott Zuhse, Instructor
Micro Matic Dispense Institute