Of condensers, math and noobie angst

[stillanoob]

Hi All,

Now that the pot/cap/lyne arm of my first still is almost done, I am starting to thing about a condenser. Naturally, my head is spinning with all of the possibilities. Liebig, worm, shotgun, cold finger. Water usage is my number one priority, after sufficient cooling of course. What I am trying to get a grasp on is how much cooling water is required. If it was say 50 gallons maybe I could use the over flow to water or wash something. If it is 500 gallons, that is too much to productively use.

I will be using a propane burner on a 12 gallon pot still. What would be the maximum input power one would want for a stripping run? Knowing the input power makes it possible for me to sensibly try to size my condenser. If we say around 5.5kW of input (as I see some heating elements out there on still sites) that would be around 19k BTU's. That is a small fraction of a typical propane burner and seems about right, a fairly low flame, maybe need a simmer plate. Of course, electric is about 99% efficient and propane is not so more BTU's will be required in actual use.

Lets take a look at a stripping run. If we start with a volume of 10 gallons of wash at a start temperature of 55 deg/F and we stop the run at about 190 deg/F, we need about 3.74 kWh or 12.7kBTU. I have no idea how much energy is lost in the cap/lyne arm and so on but if we guess we need to dissipate 80% of that in the condenser, say around 10k BTU. With 15 gallons of water surrounding the worm, that gives us about an 80 deg/F rise in temperature, so if we started around 55 deg/F we would rise to 135 deg/F. Is any of that even in the ballpark?

From a purely instinctive point of view, I am thinking of about using a 15 gallon keg that I already have. The top has been cut out and it already has a 1/2" nipple welded near the bottom. I used to use it as a brew kettle. I would weld three more nipple in it to make a flake stand. I am torn between using 1/2" and 3/4" copper tubing. I lean towards the 3/4" but it feels like that will be more of a challenge to form than the 1/2". If I did 10" turns and did 6 turns, that would give me somewhere in the neighborhood of 16' of tubing. Especially of 3/4" that feels like it would be enough.

I'm perfectly willing to make another type of condenser other than a worm. I have had some experience wrapping coils of copper tubing and it isn't easy. If possible I would like to avoid putting a pump in the mix as it makes a failure point that can't be worked around. Back when I was making a lot of beer I made a RIMS setup that essentially you could put grain in one end and got wort at perfect pitching temperature out the other end. While it was fun and cool it was complicated and a failure could make a real mess of brew day. So I would prefer something that didn't have a pump but I could be talked into it. I just happen to have a small radiator, about 8" by 16" that I could use as a cooler.

Once again, I appreciate you hand holding an anxious noob!