Fermenter Chiller Question

[rdavidw]

I have four 30L Speidel fermenters and am building temp controllers that I can run on two of them at a time. All four are wrapped in Reflectix, and I am getting two high/low controllers, two heating pads and two stainless 3/8" coils to mount in the Speildel from the lids with a thermowell in each for the two lids. Both coils run to a 5 gal bucket in a mini fridge with a pump for each controller and coil. I am mounting everything on two of the lids so I can rack to the other two if I am not using them for wine, mead or whatever.

The opening to the Speidel fermeter is about 5"". Could I split 25' of 3/8 stainless tubing to make 12.5' coils in each? That would give me about eight 4" loops spaced about an inch apart in each. Is that too little or should I build 25' in each? I ferment 5.5 gallons with a room temp from 70 to 76. I am going to use cheap 400 gph fountain pumps that I would guess push about 50~75 gph through the coils. I want to have a separate target temp for each and am not looking to lager, but may try it. I wouldn't mind being able to cold crash but I don't think the mini fridge is up to it.

My other question is should I run just tap water in my cooling bucket? I don't think the mini fridge will be able to freeze the water in the bucket but if it can should I add cheap vodka to the water or just add some table salt?

Thanks for the help!

 

[tstanonis1]

I would add food grade propylene glycol. It will keep your water from freezing if used in the right concentration. 30% glycol and 70% water will keep your water liquid down to around 0*F. It's food grade so If by chance you have an accident of some kind and you end up consuming some, then it's not a problem. It's also safe to put down the sewer lines when your done with it.

A salt solution would also work down to 20*F however... salt water is abrasive. you run the risk of sandblasting all the parts it touches to the point of a breech in materials. Also, your first point of failure would probably be your pump seal where the shaft comes through the pump to the motor.

 

[rdavidw]

I would add food grade propylene glycol. It will keep your water from freezing if used in the right concentration. 30% glycol and 70% water will keep your water liquid down to around 0*F. It's food grade so If by chance you have an accident of some kind and you end up consuming some, then it's not a problem. It's also safe to put down the sewer lines when your done with it.

A salt solution would also work down to 20*F however... salt water is abrasive. you run the risk of sandblasting all the parts it touches to the point of a breech in materials. Also, your first point of failure would probably be your pump seal where the shaft comes through the pump to the motor.

Great advice, thank you. It's an open loop system and I am expecting some evaporation over time. Will the glycol evaporate over time as well or will I just have to top up with water?

Thanks again - also, any thoughts on if 12.5 feet of 3/8" stainless coil will be sufficient in 5.5 gallons? Thanks again.

 

[tstanonis1]

no the glycol is more like and oil, it will not evaporate off but the water may over time. you may need to top up with water but you shouldn't lose that much I would imagine. there are hydrometers and refractometers that can take samples of your solution to tell you how concentrated it is. there are also charts you can google for the glycol. just make sure you're looking at propylene glycol and not ethylene glycol. Do not use ethylene glycol! it is what they use in cars and it will kill you!

the length of your tubing in the fermenter shouldn't be a problem. the more surface area in your fermenter the quicker it will exchange heat, but you're not trying to cool your beer down from boiling from what I understand you're just trying to maintain the temp so you should be fine.

If you have any exposed lines to warm air you might want to insulate them the best you can. also keep in mind that when pumping fluid through your system it will create friction heat as it travels around and back. it is possible that your water temp could rise if your pump is on all the time. you would have to make sure that you have enough surface area and cooling capacity in your cooling unit to keep the water solution at the temp you need to maintain.

that may not be a problem if you have your pump set up to only cool when needed on a thermostat. during the off cycles when the pump wasn't running your fridge would maintain your water tank at your desired temp.

just try it, you can always change your set up as needed if you see it's not working right. you can even insulate your fermentors. A box made of styrofoam would work good or some sheet foam insulation made into a custom jacket around them. It would also help to keep light off your beer so win, win...

I work with chillers and chilled water systems for a living. your actually making me feel like a monkey because these are things I haven't taken the time to do myself in my own set up. Controlled fermentations temps are important and I've just been lazy. I did get a fridge and put a controller on it for this purpose but only because I wanted to lager a batch and it wasn't an option without it...