Dual coil immersion chiller

I don't post a lot on here because I'm still new to this so I thought I should contribute at least something. I've never seen an immersion chiller like this, maybe there's a reason for it, but I thought it would be more efficient to have 2 coils using one copper tube and stretch the coils to almost the full height of the wort; we typically do 5 gallon batches, so the coils are stretched to 10" and brazed to steel rod bracing.

The inlet leads to the inner coil and it winds downward to the outer coil, then winds up the coil and to the outlet. We'll use this with a big ice bath for the kettle and hopefully have the wort cooled in just a few minutes. Total cost was $40. What do you guys think? My friend and I just finished it and it still needs a good scrubbing, but it's structurally complete.

Looks good, very clean, you got a lot of surface area there. What the total length of coil?

Sure hope that's stainless steel...

I wouldn't have brazed the rods together either. Silver solder, or electrical welding would have been a better choice. You need to use food safe welding methods when you're getting in contact with the wort. Not sure if the powdered flux is food safe once used. You could grind away the surface in the weld area, as well as where the flux was in contact. But, I'd still be concerned.

It looks like the coil is copper. Bad idea attaching steel and copper. In general you need to be careful about attaching dissimilar metals especially when in contact to water solutions. Essentially you are creating a battery, which will corrode one metal (not good things). Otherwise I like the design, just use the same metal for the coil and frame.

Yep stainless steel, 50' length, and the braze material (can't remember what kind) was approved for potable water by different associations on the back of the lable. Electrical welding would have likely burned through the tube before we could see it. The wet flux paste was for silver solder but I'll take good care to scrub it off. Will do for same metals next time

Cool. I have a coil inside a coil too. It works great. Hard to see, but mine is held together with copper wire.

I did the same but split the intake to run a parallel circuit in the two coils which then join back again for the outlet. Temperature differential between your cooling water and wort is the biggest factor to determine speed of wort temp drop. (Lots of math formulas out there that show that the SPEED of temperature change is directly proportional to the difference between temperatures. This is seen by most homebrewers in that their temp drop speed is faster from 212 down to about 100 and then the temp drop speed slows down.) As an example, a typical immersion coil is 25'. Those who have such a typical coil will attest that the outlet water is quite hot. If all you do is run that hot water through another 25' coil you really are not gaining much additional wort temp drop. But if you run cold water through two separate 25' coils, each coil gives you about the same temp differential between coiling water and wort which will give a faster temp drop.

I didn't like how much could go wrong with it and how it could be more efficient with the coils separated, so I took all of the advice here and started making a new one- all copper, separate coils, and even an additional 12' coil to sit in an ice bath between the faucet and chiller (by coincidence of left over coil). The inner coil is ~31ft, the outer coil is ~47ft.

The problem was that it's 1/4" tubing and not 3/8" because home depot doesn't carry 3/8" anymore and the last box was bought 2 days ago. I already considered how slow the water will move but I'm hoping the improved efficiency and the additional coil sitting in ice will make up for the slower speed.

I'm going to solder it all this time, not braze it like what was suggested. I have plumbers solder and flux. What solvent do you guys recommend for removing the flux? Or boil in salt and vinegar or something? Removing flux is new to me.

And btw, thanks for all the comments

Never heard of any problem with the flux.

I will say that since you're building a new chiller, use the first one as a pre or post chiller.

TXCurtis said:

I will say that since you're building a new chiller, use the first one as a pre or post chiller.

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That would have been great if I had thought of it before I cut up the old one. Oh well. Solder one more joint, give it a really good scrubbing, get 1 new hose for it and it's done.