DIY Glycol Chiller system (fermentor external)

[outside92129]

Project Description:
Adding glycol cooling system to exterior of an existing stainless fermentor and detachable from cooling unit. Kept cooling coils outside of fermentor for ease of maintenance/cleaning. Setup is easily capable of -20F below ambient, can probably do another -20 if needed. Overall very easy to do, a level 2+ project on the HBT DIY Project Locator.

Background:
My DIY conical has been working great for the last few years but during heat waves i have to cover it in ice and/or spray it down every few hours and even then the temperature approaches 80F. The conical is quite large and being short on space i couldn't get a large fridge to put it in, even if I did get a large fridge past the SWIMBO moving 10-15gal wort from the brew space to the ferment space would be very difficult.
https://www.homebrewtalk.com/f51/40-diy-conical-keg-no-welding-262336/


Parts needed:
Copper Coil (25ft)
Thermal Silicone/Adhesive (SS-35 direct from siliconesolutions.com, one 10oz tube)
Silicone caulking (two 10oz tube)
Tubing (polypropylene)
Stainless Flux (Lenox High Activity Stainless Steel Flux)
Solder (Harris Stay-brite #8)
pond pump (Eco 396)
fridge/freezer
glycol (Splash RV -50F)
Closed cell insulation (sleeping pads via ebay)
Various barb fittings and clamps
liquid vessel to fit in fridge/freezer
pipe insulation, 6ft length
STC-1000
siphon pump (optional, to prime the system)
Cole-parmer auto-sealing disconnects (optional, but clean, leak free way to separate fermentor from fridge)

Tools needed:
Soldering Gun
Drill
pliers, screwdrivers, etc


Step 1
Coil copper around fermentor and solder once each loop for strength. I pre-wet (pre-solder) the stainless and copper before soldering them together which made it a lot easier to join. Because copper is so thermally conductive it just sucks the heat out of the soldering gun and makes for some ugly joins. I hit the solder with a propane torch and the solder flowed nicely into the joint, for this project it's not necessary but it made things better looking (and stronger). I also added a barbed U-bend so the glycol input and output would be in the same direction.

To solder stainless you *need* stainless flux. There are some posts on HBT on how to do it, but if you dab some flux the solder sticks like a champ. I used lenox flux (rated up to 850F) with a soldering gun but if you want to use a torch then you'll need a brazing flux such as Harris Stay-Silv.

Step 2
Even though i pulled the copper coil tight around the fermentor the actual contact surface between the two was limited (even without the occasional gap) so heat transfer would be incredibly inefficient. I filled in the gap on both sides of the coil with thermal silicone adhesive (Silicone Solutions SS-35) to overcome the lack of contact. I didn't concentrate on a smooth bead as the entire unit will soon be covered with insulation. Any play that was in the copper is now gone and the coil is firmly attached to the fermentor.

Step 3
I bough 4 rolls of closed-cell backpacking sleeping pads, $7/ea off ebay w/ free shipping. They were 1/4" thick, 2ft wide, 6ft long. I cut small strips to fill in the spacing between coils and glued them in place with silicone caulking. An hour of cutting and gluing the gaps were done and i wrapped the entire fementor with another two layers of padding. This gave the fermentor 1" of insulation with 1/2" on the coils. I also fit the top and the bottom conical with insulation. I then sealed all the exposed edges of insulation with more caulking with a nice thick and angled lay on top to control runoff/spillage, this will prevent water/wort from seeping in between layers and turning into a nasty moldy mess. I then feed 2 lines of polypropylene tubing thru pipe insulation and attached it to the fermentor with the cole-parmer disconnects on the opposite end. I aligned the tubing inside the insulation with each other as well as the curvature of the fermentor- so when no in use the tubing wraps easily around it.

With 25ft of coil and another 15ft of tubing in the system there would be a fair amount of resistance and vertical height that the pump would need to work against, so i added a siphon to prime the system.

The finished picture of the fermentor:

Step 4 - freezer
The boring part of the project was to flesh out the freezer. I drilled 2 holes in the internal hump for the coolant lines and 1 for the pump electrical. Nothing fancy here, i took a 2.5 gal water jug from the grocery store and put the tubing, pump, and glycol in there. In my kegerator project i used an aluminum container but it pitted heavily within a month so i switched to polypro. Also for this build I originally started with a 90gph pump but it barely had the horsepower to keep flowing so i upgraded to a Eco 396 (396gph, $23 amazon) which is doing the trick nicely. This should allow me to eliminate the siphon now (which is leaking due to the cold coolant).

Step 5 - electrics
My initial plan was to use an old homedepot thermostat to trigger a relay to trigger the freezer/pump but for just a few bucks more i could get an STC-1000 and simplify the wiring as well as have a nice bright display. In my case i have the freezer plugged into the wall and only the pump into the relay. This way when the STC-1000 triggers coolant flow the freezer can supply 10F glycol instead of waiting to cool down. 3-4 years ago when i made the fermentor i added a thermowell, i finally get to use it! It's just a simple tube fit into a tri-clamp cap and cost me $4 to make. Just drill two 1/2" holes in the cap, one tube goes up for blow-off, one goes into the wort for temp monitoring (be sure to seal the bottom end). $120 retail : )


How it's working
Great! My fermenting station is outside in a shed so it can get very warm during the day, this setup is keeping my wort spot on at 69F all day (IIPA bubbling away as i write this).

Things i like

• the cole-parmer disconnects. The ability to separate the fermentor from the freezer making things easy for a single person to move around.
• I was pleasantly surprised by the quality of the sleeping pads. Shipped directly from China and they were as advertised. I'd never replace my thermarest or z-pad in the backcountry but it's a good source for cheap foam.

Gotchas

• -50F glycol can form fairly significant ice crystals/slush at 10F. If i had to do this over again i'd use a fridge instead.
• As usual i finish a lot of beer projects before a big scheduled brew day with the buddies. Finishing up a bit past midnight i didn't have time to test the system before going live. STC programming was a bit panicky as was a leak but we got things sorted out quickly.

Upcoming changes

• Remove siphon. The very cold glycol is making the internal diaphragm stiff and it barely works. With the upgraded pump it's no longer needed.
• Replace vinyl tubing. Most of the tubing is polypropylene but i have a few segments of PVC/vinyl which stiffens up when cold.

p.s. keg is from a defunct brewery.

 

[Jordo_nb]

This is a really good build, and something I would like to reference some day to build my own.

 

[Weezy]

I like it! good lessons learned shared too. Long term plans are for something similar.

As an option you could consider using 3/8" copper coil tubing, straighten it, fill it with sand to support the walls and hinder kinking, then gently flatten it by hammering it (with a plate to spread the impact over s longer length of tube). This should give us nice contact area when wound onto the fermenter.

 

[Stealthcruiser]

I like it! good lessons learned shared too. Long term plans are for something similar.

As an option you could consider using 3/8" copper coil tubing, straighten it, fill it with sand to support the walls and hinder kinking, then gently flatten it by hammering it (with a plate to spread the impact over s longer length of tube). This should give us nice contact area when wound onto the fermenter.

Then the "winding" will be a bit more difficult, with the flattened tubing, but me likes the idea!

 

[brianbrinley]

this is perfect, exactly what I was looking to do! looks beautiful

 

[Minbari]

pretty close to my plan, except I plan on using 50' of 1/4" tubing. the smaller diameter should give me about the same contact area on the side of the fermentor, but with more length, it should equal better conductivity. 1/4" is much easier to shape by hand too.

looks really nice!

 

[baer19d]

This seems like a good project so I figured I'd bring it back to life.

 

[outside92129]

I got some questions so i thought i'd re-post the questions:

wondering if it will get the beer down to cold crash temps (mid 30's).

I don't cold crash in the fermenter so i haven't tried it, everything goes to the cornies which may or may not sit out. I generally use med-high flocculent yeast, and also quickly chill the wort after boiling and don't have haze issues. Thinking of performance, this time of year i can easily get down to cold crash temps. In the summers the unit does 20F less than ambient (southern california.. 90's) and judging by the compressor/pump it's not working very hard. So 40F less than ambient is well within range.

recommended changes since you've built it?

In my post i mentioned switching to polypropylene tubing, i'm now looking for a replacement for that too. at the cold temps of the freezer it seems to be brittle and my barb fitting connectors are causing cracks in the tubing. I've put band clamps over the tubing at the barb which seems to be working, but it's a stop-gap until i can do some more research into more suitable tubing.

My freezer container / cold reservoir could use some more attention from me as well. Right now it's just a 2.5gal water container with a hole cut in it for the tubing and electrical. It jiggles around too much when i move the thing and during the sloshing around it leaks out. I also used aluminum in the beginning for better heat transfer but i couldn't find a container that would stand up to the environment. A nice stainless container would be great but i can't find one in a cost effective way.

 

[bausermant]

I'm planning on something similar a diy glycol chiller. A/c unit and a cooler. But I'm going to get stainless steel coils and put them in the fermenters. Then insulate the outside of the fermenter.

 

[outside92129]

Well it's been a couple of years on, the last several months have been a little slow on the brewing front, but some updates on the system:

• It's still going strong. No major issues, just the occasional crack in the tubing where the barbs plug into the coolant tubing. I'm going to replace all the tubing with teflon tubing (i just read the Elon Musk book and there was a comment about PVC/teflon/HDPE tubing at SpaceX).
• The freezer reservoir, aka the bucket/jug, needs to be upgraded. Not the easiest to refill and it sloshes around too much for my taste. I'm thinking i can make a replacement out of copper, it's easy to work with and has great thermo conductivity...
• I'm going to sleeve the insulated coolant bundle. The soft insulation catches on things and tears. For my beer tower i used heat shrinking plastic, i'll do the same with the bundle.

My original post didn't make it too clear how the internals of the freezer were laid out. Everything's put away (it's sad beer time here) but i posted a schematic which may be easier than a picture to read.

 

[homebrewdude76]

What size pump are you currently using. I noticed you mentioned it was upgraded.

 

[outside92129]

I started with a 90gal/hr pump but that was barely enough to over come the resistance and gravity. It's now on a Eco 396 pump (400gal/hr) which flows well.

 

[Jakub Barzdo]

Can I ask if it will be good idea to use solder on whole copper coil length insead of thermal paste?

 

[madscientist451]

Thanks for posting, great pictures and explanation.

 

[helterscelter]

Can I ask if it will be good idea to use solder on whole copper coil length insead of thermal paste?

I followed this post to do my own sanke keg, and originally planned to do as you are asking.. soldering the entire length of the copper tube to the keg would be much better imho, then using thermal conductive silicone. the problem i ran into, was being able to heat the keg and tube sufficiently to do the soldering, and not heat it so much that the solder took too long to solidify all while preventing other runs of the coil from coming unsoldered due to heat soaking the stainless/copper and re-melting the solder.

Another issue I ran into was the relatively unevenness of my keg -- the one I used was in worse condition than the OP's. it suffered through much beating and many dents in it's lifetime, which made some parts of the keg more flat than round and in some places very much dished in.. since I'm using sanke fermenter conversion kits rather than welding on a cone, pounding out the dents wasn't an option.. due to the irregularities, I couldn't get the copper to lay flat/close enough to the keg surface in all locations in order to be able to solder it..

the thermal paste that the OP recommends is a little expensive, but it does work very well.

if you are able to solder all the way around the whole keg/coil and can put enough solder in there to fill in the gap at the keg/coil contact surface, I think that would in deed be the way to go.. (though I wonder at the relative difference in cost of that much silver solder vs the cost of the thermal silicone.. )

 

[Jakub Barzdo]

though I wonder at the relative difference in cost of that much silver solder vs the cost of the thermal silicone..

Silver? Tin will be enough?

 

[Stealthcruiser]

Silver? Tin will be enough?

Methinks, getting a bond to the Stainless, will require Silver solder.........
I could be mistaken.