Chest Freezer Fermentation vessel problems/questions

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My recent brews have been in a cupboard with my Chubby fermentor sat on a heat pad.. did the job ok..

With an eye to doing some lagering down the line , I whipped out an old chest freezer that can hold two chubbies.

I hooked it up to an inkbird with a small fan heater and the freezer turned down to its lowest setting. dropped two chubbies in to ferment at 18C and set the inkbird accordingly, taping the temp probe to the outside of one of the chubbies insulated with a sponge..

I know I have overshoot issues using the fan so a 60W tube heater is on its way to deal with that.. however the cooling cycle is driving me mad..

I have an Ispindle in one of the chubbies feeding me the wort temp..

The inkbird is set for 0.3C either side of target. and its probe temp never drops below the set 17.9C .
However when the cooling cycle is engaged the wort temp keeps dropping well down close to sub 17 C and i have had to switch the cooling cycle off to stop it cold crashing..

Im thinking i firstly need to create a 50mm wood platform to insulate the fermenter bottom from the cooling surface .

Do i need to create a wider airgap around the fermenters as I only have 5mm gap between the freezer wall and the fermenters?

Or is this freezer just too agressive at the cooling thing?
 
Lag. I think.
By the time the freezer had an effect, it has build up to much "cold", which doesn't go away instantly. Water does not react to/absorb the air temp changes very quickly.

Perhaps an air fan might help?
Set the freezer to run less cold. (up or down only gets confusing)?

Edit. Typos
 
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Lag. I think.
By the time the freezer had an effect, it has build up to much "cold", which doesn't go away instantly. Water does not react to/absorb the air temp changes very quickly.

Perhaps an air fan might help?
Set the freezer to run less cold. (up or siren only gets confusing)?
i have the freezer stat turned right down

i was thinking about setting up USB fans on both the hot (Once I have teh tube heater in place) and the cold side to keep the ambient temp as even as I can.
 
I always have at least one fan in my chambers. My chest freezer has two, one at each end. It makes a big difference as air is a good insulator so you need to push it round. What you set the freezer to shouldn't matter as even at it's warmest setting it will be trying to get below zero. It's a target not a speed setting.

And yes, insulate the FV from the bottom so you are controlling it by air temp.
 
Adding a fan to circulate the air will make a massive difference - the fermenter will cool faster and you'll only get a little overshoot. 120mm PC fan on a low RPM works fine.

I would also highly recommend keeping the fermenter from touching the bottom of the freezer using a stand or even just a bit of wood as even once the freezer has turned off it'll still be conducting heat away from your fermenter.

Finally I'd say only allowing 0.3c hysteresis is small - you really don't need to be anything like that accurate. 1C will work just as well, and stop the freezer coming on so often.
 
And for future readers. If you just want to control fermentation temperature.

A simple coil, ice box and a pond pump is simple to build, brilliantly effective, cheap to buy and run. And lets be honest in the UK, you only need it twice a year (if you are really can drink). So for the rest of the year you have a nice cooler box for your sarnies & a pond pump for washing hoses out. And a massive space to store malt in. 👍🏻👍🏻
 
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Adding a fan to circulate the air will make a massive difference - the fermenter will cool faster and you'll only get a little overshoot. 120mm PC fan on a low RPM works fine.

I would also highly recommend keeping the fermenter from touching the bottom of the freezer using a stand or even just a bit of wood as even once the freezer has turned off it'll still be conducting heat away from your fermenter.

Finally I'd say only allowing 0.3c hysteresis is small - you really don't need to be anything like that accurate. 1C will work just as well, and stop the freezer coming on so often.

Re: the stand, make it strips rather than a single piece so that air can circulate under.
 
By experimenting with Keglands Rapt pill hydrometer I have found it is better to stick the inkbird or similar control sensor to the outside of the fermenter "WITHOUT ANY INSULATION"( sponge or foam). For better control of temperature.
 
By experimenting with Keglands Rapt pill hydrometer I have found it is better to stick the inkbird or similar control sensor to the outside of the fermenter "WITHOUT ANY INSULATION"( sponge or foam). For better control of temperature.
Interesting! Im trying to get my head around why no insulation would help..
Does this method result in a Hybrid temp on the probe. i.e. its influenced by both the fermenter and the air temp?
 
My guess is that by insulating the probe on the outside of your fermenter the air around feremter will be colder then the liquid inside, so the cooling will continue after the sensor triggers the cooling to stop. When the liquid catches up with the temperature outside, the liquid will be cooler than the set temperature. Then your heater, if you're using one may kick in. The result I noticed was the temperature fluctuating above and below the set temperature.
It was only when I started using the Rapt pill that I could see this in real time.
If you wanted a cold crash quickly it might be worth putting some insulation around the sensor.
I prefer to cold crash more gradually over a period of several days.
 
I've probably said this before but I don't control the temperature of the beer during fermentation I monitor it whilst controlling the temperature of the FV. This allows the wort temp to naturally rise and fall as it goes through fermentation without me trying to fight it to be exactly 19c or whatever. It avoids the oscillations completely and to me seems more natural to let the yeast do its thing. You can also monitor the progress of fermentation.

I used to cold crash by monitoring the slope of the temperature drop of the beer and dynamically changing the FV temp (via software) to optimise this rate and avoid overshoot. Now I just do the same as fermenting and let the temperature drop more slowly to the desired crash temp.
 
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