Originally Posted by pizzaman
He has the two pvc pipes going from his diy walk-in cooler to the bar. I believe the closed air loop is created by blowing cold air through one pipe(from cooler to bar) and sucking presumably less cold air back through the other pipe(from bar to cooler). I would imagine the beer lines are encased inside the pvc which has cold air blowing from the cooler to the bar, and this is what keeps them cold. That's how I understood it anyway...
Yup... that's exactly it.
I have a 3 inch PVC pipe that carries the lines and a 2 inch PVC pipe that is the return... both are wrapped with pipe insulation. Plus, they go behind a basement wall and they a foot or two off the basement floor so even on a hot day, those pipes stay pretty cool naturally.
The pipes both come up from under the bar, through the bar top, and into the coffin box. The coffin box is then insulated and sealed pretty much airtight with silicon and weather stripping around the lid.
The lines are somewhere between 30-35 feet long and to be honest, i shut the fan off a while ago and haven't used it since. Out of habit I draw the lines clear before I start pouring beers. If it's been a few days, I think the beer in the line just goes a little flat so I dump it. It's just barely half a glass so it's a waste but I don't think it's the end of the world... and then just by pulling beer from teh cooler, the lines chill and stay chilled.
So while I have a "closed loop", I don't actively circulate air through it. I just don't think it's needed.