keeping 2 separate fermenters the same temp in chest freezer?

[Rivenin]

Just moved into my new house and am getting the garage setup and should be brewing my first batch in the new place by the middle of next month.
However, one thing i never really tackled was getting two fermenters the same temperature.

I have a 5cf chest freezer... said chest freezer fits 2 carboys just fine. 2 buckets however will not fit.
my fermenters consist of a 6g better bottle, 2 3g better bottles, 2 6.5g glass carboys and 2 5 gallon glass carboys. a combo of one of each fits just fine... so it might be the variant of having a lag from the thick glass vs the thin plastic making it so far off from each other? and by far off, i mean at least 10* at times.

i have them at the same height via a 2g bucket at the bottom of the chest freezer, which helped... but i am now debating how to make this consistant?

1) i was debating was to buy another 6g better bottle and keeping them at the same height via building a platform and since the quantity will be the same in each, i should only need to use my thermowell in one carboy and the heater going between both in the middle (lasko heater)

How do people normally keep the same temperature with their split batches?

 

[Nagorg]

I use the same type of fermentor and have them at the same height. While I dont know what difference there may be between them, I dont worry about things I cannot affect like that. I have a single temp probe from my STC-1000 controller build taped to one of the fermentors and covered by two layers of koozie as a shield against ambient temps in the fermchamber. I can only control the cycling of the freezer or heater that's plugged into the controller. Since the chamber is the same, that's about the best I can hope for.

If you really need to control temps separately, I think you'd need multiple fermchambers and controllers.

So far, I cant tell that there's been any issues or notable differences between the fermentors.

 

[broadbill]

Do you use a fan to move the air around the fermenters in an effort to minimize gradients? I do a tiered approach in my 5cf chest freezer (had to build a collar out of blue insulation to make some extra headspace) and the fan seems to do a good job of equalizing everything.

 

[Rivenin]

only when the heat is going from the heater. But that is Something that didn't even cross my mind...
I have another 7cf chest freezer that can fit two fermetners at the bottom... but it's my kegerator. So i might try a fan and see what happens!

 

[broadbill]

only when the heat is going from the heater. But that is Something that didn't even cross my mind...
I have another 7cf chest freezer that can fit two fermetners at the bottom... but it's my kegerator. So i might try a fan and see what happens!

Give the fan a shot, I bet that fixes it. In a pure stoke of luck, I made my temp controller with an extension cord that had 3 plug outlets at the end. The temp controller kicks both the fan and the chest freezer (or heat wrap) on at the same time. I've read that other people keep a fan on all the time which may be a better way to go.

Another thing I thought of with rereading your post is you may be right about the glass vs. plastic...I totally see the glass insulating a bit...

Good luck!

 

[cegan09]

In general, don't worry about it. You may see a slight variation, but not a ton. If you're data hungry like I am setup a BrewPi for the fridge and throw a thermowell in each fermenter. Use one as the target and the other as just a data point. You'll see how they differ.

Agree with adding a fan. Keeping the air moving will minimize the gradients and create a more even chamber temp.