Glycol chiller setup questions

[phillip_h]

I recently put together a DIY glycol chiller with a 5000 BTU window unit and an ice chest. It's currently doing a great job of keeping the fermenter at 60°F in a garage that it about 80-85°F.

I have it hooked up to a Johnson digital temp controller and I'm keeping my glycol reservoir at about 36°F. The controller shuts the AC off when it gets down to 36° and then it turns back on when it gets up to like 40°. I set the short-cycle delay to 8 minutes so that it doesn't wreck the compressor.

It seems like the window unit is running pretty much any time I check it. Is it typical for the AC to be running this much, or should I make some adjustments in my settings?

 

[hvjackson]

You don't want the compressor running all the time. It won't last long.

If you are fermenting at 60 °F I don't think you need to have your chilling water all the way down to 36 °F. Try setting it to 50 or something, that will cause you to lose a
lot less coolth to the environment. If you want to cold crash the fermenter you can drop it down more then.

Is there good airflow around the AC? Make sure you haven't blocked any of the vents on the condenser (hot) side. There is usually a fan to draw air through the condenser fins. If the condenser is very hot the AC won't reject heat well and the compressor will have to run more.

Is your ice chest pretty well sealed? If the top is open than you will have problems keeping heat out.

Is the evaporator coil from your AC unit completely submerged in glycol solution? If not you should rearrange things so that it is.

Is the water circulation pump to the fermenter also running a lot? I doubt there is very much heat gain to the fermenter from the environment but it can't hurt to insulate the fermenter and the chilling lines as well.

What glycol/water mixture are you using? You want about 1/3 or 1/4 glycol, the rest distilled water. Glycol is not a very good heat conductor so if you use more than that you are sacrificing efficiency.

 

[phillip_h]

Lots of info here - thanks!

I just raised the temp on the controller to 50°. Let's see how that works.

There's plenty of airflow around the AC unit, so that's not a concern.

There are a few tiny openings on the cooler that I could probably insulate, but it's mostly sealed. It holds temperature pretty well until the pump kicks on.

The evaporator coil is mostly submerged in the glycol solution. There's maybe 2" where it isn't in contact with the liquid.

The pump doesn't run all that often. The fermenter temp stays pretty close to where it's supposed to.

I'm using a 1/2 ratio of glycol to water - 2 gallons of glycol, 4 gallons of water. If I added a couple more gallons that would probably completely submerge the coil.

 

[SanPancho]

I'm using a 1/2 ratio of glycol to water - 2 gallons of glycol, 4 gallons of water. If I added a couple more gallons that would probably completely submerge the coil.

NO NO NO NONONONONONOOOOOOOO. thats way too much. if you're only going down to 36 then you might be at only 25% glycol. glycol does not transfer heat as well as water. it just protects against freezing.

two things-

first- figure out where you want your glycol temp to be vs where it can be. glycol chillers are typically medium temp systems. (-20F to 40F i think?) and home AC is high temp. (40F+) 36F may be maxing out your unit. the lower you get in the unit's temp range, the less BTUs it produces. actual contact between glycol and condensor helps, but you're probly at the max. might wanna do some research on that.


second- look up a glycol table. it'll tell you what you need in terms of glycol mix % to get a freeze point. so typically glycol is at 28F, so then the refrigerant in the condensor should be at like 15F, so glycol freeze point should be like 5F to make sure it doesnt freeze. but in your case, you can probly do more like 10-15F freeze point.

but at 50%, you're way overtaxing the system. glycol is way inferior in heat transfer vs water. its only there to be anti freeze. only use as much as you need.

also make sure you know the concentration of your glycol, the good stuff is high 90s, but ive seen some that is only 80%. a refractometer can be used for a good estimate on mix %.

i hope you bought food grade glycol. and buy food grade ink/dye if you can get it. some weird color like green or blue so that if you ever get a leak into the fermenter, you immediately know it because your beer is weird color. even food grade glycol isnt something you want to drink. and non food grade is poison in many cases.

 

[phillip_h]

So, are you saying that I have too much glycol in my system? I did some research before I set it up and most of what I read called for a 30-35% glycol mix. That's about what I have.

I bought food grade glycol (Propylene Glycol - 1 Gallon - USP Certified Food Grade - Highest Purity, Humectant, Fog Machine, Humidor & Antifreeze Solution, DIY, Kosher https://www.amazon.com/dp/B01MS8F1UW/?tag=skimlinks_replacement-20)

 

[augiedoggy]

So, are you saying that I have too much glycol in my system? I did some research before I set it up and most of what I read called for a 30-35% glycol mix. That's about what I have.

I bought food grade glycol (Propylene Glycol - 1 Gallon - USP Certified Food Grade - Highest Purity, Humectant, Fog Machine, Humidor & Antifreeze Solution, DIY, Kosher https://www.amazon.com/dp/B01MS8F1UW/?tag=skimlinks_replacement-20)

I use the same exact stuff (cheapest on ebay btw) yes you have too much... unless you are going below freezing you only need a little to help keep the water from growing bugs... I use 1 gallon of glycol and about 4 gallons of water mixed myself... works well even when bringing my chiller down to 30.
ou havent mentioned how you have insulated your fermenter??
frankly im surprised no one asked.
I found that the amount of time my chiller runs really depends a lot on how well the conical is insulated. I have 2 layers of foil faced bubble wrap around mine right now but may actually increase that. In the winter months with 65-75 ambient it works great for lagering but in the summer my chiller also runs a lot.

 

[phillip_h]

At the moment I'm using the neoprene jacket that came with my Ss Brewtech BME Chronical. I know that it's not the most effective insulation, but it seems to work fairly well.

 

[SanPancho]

from what you stated earlier its too much. the best thing to do is the figure out what temp you want the glycol to run at. 28F is typical, but 30, or 35 is fine too. the lower the setting, the colder you can crash cool.

once you have your temp decided, then subtract another 5-10F and use that as your freeze point. the glycol chart will tell you what % of glycol to get to that freeze point. only use as much glycol as needed, never more.

a refractometer will give you a brix reading to check your mix %. hydrometer doesnt work. only refractometer.