Ultimate Corny Keg Fermenter: Internal Coils and Glycol (chilled water for now)

[BBBF]

I'm a week into the maiden voyage and a year and a half into the build (lots of down time). The driving force behind this build was that I stumbled onto a water chiller that I picked up for $0.99 and had to justify its existence. I also was in procession of two, 10-gallon cornies that I enjoy fermenting in. External cooling seemed like the easiest route to take but figuring out internal coils seemed more fun. The goal was internal coils, but I wanted them removable for cleaning, I wanted to continue being able to ferment under pressure and I also did not want to permanently damage the kegs. Utilizing the keg posts would have been nice, but you need to flare the SS tubing for the o-ring to seal, making in a fixed coil. Going through the lid was ideal, as the lid could be removed for leaning and replaced to needed.

Here’s the current state of the project and I’ll add some build more build pics in posts below:

 

[apache_brew]

Curious to see what the coil configuration looks like for stock cornies.

 

[BBBF]

Curious to see what the coil configuration looks like for stock cornies.

I made three sets of coils. The first two came from some heat exchangers that I purchased on ebay to repurpose for this project. The diameter was good, but the length was not. I cut the tops off and using 1/4" socket fittings and SS coiled tubing, I soldered extensions onto them. I used John Guest fittings to test for leaks using municipal water pressure, followed by 15 PSI of compressed air. There were no leaks. I'm still nervous about sanitation, but I can drop them in the boil like an in immersion coil.

The third coil was made from the extra SS coil. I tried to do a fold back design like the Anvil chiller. I made two mistakes here. First, I made the folded back part too long. This will make more sense when I show the lid modifications. To fix this problem, I started folding the coil back again, however I did it in the wrong direction. I was able to undo it, but despite having a fancy tubing bender, they now look like crap. I may redo it at some point, but it is still functional and nobody can see the kinks when it is in the fermenter.

The true coils can only fit in the 10 gallon kegs. The fold back version can fit in a 10 and a 5. A future test will be to do a side by side test of the two coil types to see if there is any significant difference in maintaining fermentation temps.

 

[BBBF]

There are several challenges to mounting the coils to the keg lids. The first is that the lids have to be tilted on an angle to be inserted into the lid opening. There is trigonometry involved. The overall length of your coil is limited by the diameter of the keg and the angle of inserting the lid and it isn't going to be anywhere near long enough. My plan was to limit the amount of tubing that was actually coiled/folded back on itself and allow for that portion to be raised and lowered so that the required lid angle could be achieved. Unfortunately, I decided not to do the math and I eyeballed all of this, which is why I messed on on the fold back version. On the coiled version, I was able to compress the coils further than shown below and cut off the extra length. The lids are a bit clumsy to get it, as they only if you tilt it at the correct angle and rotate it into place. It gets easier the more times you do it, but no where as simple as those triclamp fittings on the top of conicals. The arrows I drew on the keg help.

Next problem to solve was how to mount the coils so that they can be raised and lowered. A simple rubber #2 stopper would be easy, but I want to be able to ferment under pressure. I decided to use compression fittings and BobbyM/brewhardware.com had welding spud compression fittings. I decided to solder these onto keg lids, but even that presented some problems. There is not a lot of real-estate on every lid. I had to find one that either had no PRV or that the PRV was not centered. Also, the latch needed to be wide enough to clear the tubes. Luckily, I found a few that would work. I also needed to make a racetrack version for one of the 10gal kegs. I thought that would be easy because my lid did not have a PRV, but it was a little more problematic because those lids are slightly domed and I needed the spuds to line up in parallel. A block of wood and a hammer got me close enough.

I'm currently using small o-rings in the compression fittings. Once I decide if it is better for the coils to be 1/2", 1", 2", etc. off the keg floor, I'll switch over to the permanent, SS ferrules.

I use a brass compression/NPT fittings and a brass barbs to connect the hoses. For simplicity and cost, I had wanted to use push connect fittings, but they could not latch onto the SS tubing. I later learned you could score the tubing with your pipe cutter and give them something to grab.

 

[BBBF]

Insulation...

I don't know why my dad had sheets of 1/2" neoprene. I would have liked to have gone a little thicker, but they were free for the taking. The sheets did not have nylon backing for strength and sewing, so I used black duct tape to reinforce the edges and make it into a sleeve. I'm also using Inkbird heat mats with the fermenters. Instead of pulling the sleeve over the heat map and temperature probe, I decided to instead glue a zipper onto the neoprene sheet, with a contact cement for wet suit repair. It's sturdy-ish, but you can tear the zipper off if you are rough. Sewing a zipper onto nylon backed sheets would have been the best route, but did I mention the neoprene was free?

I used leftover scrap to insulate the chiller reserve. My tubing is all insulated with off the shelf foam. My manifold sweats and needs some insulation and I would like to better insulate the tops of the fermenters.

 

[BBBF]

Manifolds, Valves and Controls...

I went a little cheap on the panel enclosure. There are three Inkbird controllers so that I can control cooling and heating of three fermenters. The controllers send a signal to one of the three solenoid valves hanging off of repurposed beer manifolds or to a relay controlling the heating mats as needed. Not shown is a small valve on the open line. Coolant is always recirculating through this system, but it needs a little resistance so that there is enough pressure so that it doesn't flow right past the open valves.

I do not like that my chiller is always running. After paying a couple electric bills, I will want to rebuild the controller. The chiller has an option to be run remotely. I'd like to add a 4th controller that will monitor the temperature of the reserve so that it can keep the coolant within a much larger range than the internal controller, which is only a degree. Power to the chiller will be cut off unless it the reserve has gotten too warm or the fermenters have gotten too warm and require the chiller's pump.

I'd also like to add glycol. This chiller only goes down to 40F, but by playing with the calibrations, I can trick it into thinking 32F is 40F and with an external controller I may be able to go even lower. Or maybe the internal controller will override the remote one, but I think I can get close enough to freezing that I should have a little insurance that things don't.

 

[apache_brew]

Very cool! I have a very similar build I’m mustering up in my head using 1/2 bbl kegs, 6” tri clamps, temp twister coils, Inkbird 308s galore, a brand new self contained vending machine refrigeration unit for glycol, and submersible pumps for each fermenter.
Those weld in compression spuds Bobby sells look fantastic. I’m definitly ordering some for the coils.

 

[BBBF]

I will be jealous of that 6" opening. I just opened up the racetrack lid to dump in 3lbs of black raspberries and 2lbs of honey.

 

[Gruel]

Very nice! For my fermenter I started with an internal loop, since it gives the best thermal coupling to the liquid to be cooled, but handling was kind of clunky, and in the end I convinced myself that the thermal coupling of an external loop is good enough.

For the kegs I didn't even try internal loops, and in the end also went away from attempting to individually insulate them. I would have liked to keep everything modular and with as small a footprint as possible, but there were just too many openings and junctions and uninsulated surfaces where humidity could get in and condense, and my chiller is just not up to the task of dehumidifying our apartment. So in the end I stuck the kegs (with external cooling loops) into a big foam box, the (thermoelectric) chiller is in a plastic case, just like your controllers, and there's only two lines from the chiller to the foam box that need to be insulated.

With a powerful enough chiller and/or a dry enough space, your setup should work. But if you are trying to cool below the ambient dew point you will have continuous condensation, and might end up effectively paying for electricity to dehumidify your brewing space during the Chicago summer. If the chiller is efficient enough, it's no worse though than running an air conditioner for the same purpose.

 

[BBBF]

Very nice! For my fermenter I started with an internal loop, since it gives the best thermal coupling to the liquid to be cooled, but handling was kind of clunky, and in the end I convinced myself that the thermal coupling of an external loop is good enough...

With a powerful enough chiller and/or a dry enough space, your setup should work. But if you are trying to cool below the ambient dew point you will have continuous condensation, and might end up effectively paying for electricity to dehumidify your brewing space during the Chicago summer. If the chiller is efficient enough, it's no worse though than running an air conditioner for the same purpose.

Thanks. I was watching your build and trying to decide if I wanted to go with internal or external cooling. I obviously went in a different direction, but it your thread was helpful to me and provided me with motivation.

The specs on my chiller say it is 1150W, which calculates out to 3924 BTUs and it has a 2 gallon reserve. I did not do the math to calculate if he chiller is up to the job of removing enough heat to bring all three fermenters from ambient to cold crashing temps in a reasonable time. I'll do that someday when I'm bored enough to look up the formulas again. The 1/5hp Brewtech Glycol Chiller is only 1450 BTUs, with a 4.75 reserve. My chiller is plenty powerful enough, but the stock controller limits how low I can go. For now, I'm happy for lagering temps. To be determined if I can still cold crash in the middle of the summer.

Unfortunately, I'm already paying to dehumidify my basement in the summer. My lines are pretty well insulated, except for the manifold. I have to do a better job there. And the top of the kegs are uninsulated. I'm not sure how much it is needed, with 4 gallons of gas separating the top of the fermenter from the beer inside. If it sweats or the heat loss seems more noticeable, I'll make something or stack some towels and blankets on top of it.

 

[Gruel]

The latent heat of water is about 2200kJ/kg, or kWs/kg, so with 1100 W or ~3800 BTU/hour cooling power you can condense half a gram of water per second, give or take. That's 1800 gram or half a gallon per hour, which seems a decent amount. It's half of what an 8000 BTU/hr air conditioner could do.

Using this calculator, to go from a dew point of 15C to 5C (I'm guessing that your A/C will not give you a dew point lower than 15C), you have to remove about 6 gram of water per cubic meter. If your basement is say 500 sq.ft, and 10 feet tall, it holds about 150 cubic meter or an extra kilogram of water. Your chiller can do twice that per hour, so it could keep up with air leaks of two air exchanges per hour. I guess that means it's not hopeless.

In my situation, with an anemic few hundred W peltier chiller in 1000 square feet, it was just hopeless.

 

[edwardgribbins]

BBBF, your profile picture, what is it from?