Fermentation Temperature control with fridge and fermwrap

Describe your system and processes, and post your config file.
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ostrtj99
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Joined: Mon Apr 07, 2014 9:35 am
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Fermentation Temperature control with fridge and fermwrap

Post by ostrtj99 »

Hi all my name is Trevor and I'm new to this forum. I'm sorry if I am asking a question that has been asked before but I can not find the answer. If this has already been discussed could someone send me the link please?

I have the BSC 460. I ferment in a mini fridge and have a fermwrap that I attach around the fermenter for heating.
I have made a box with an outlet with two SSR each one controls one of the outlets. One for fridge (cooling) and one for heating (fermwrap)
I have a thermowell that the temperature probe goes into during fermentation.

This is my first run on using this set up and I am having trouble with temperature reading. The temperature is reading approx. 10 degrees higher than it really is. It was reading the temperature accurately when it was set up in the fridge before fermentation. Now that fridge and fermwrap are plugged in the temperature has been off by 10 degrees. Is this a magnetic field issue? I have read about this and have grounded my bcs which did help with another temperature probe that was running 50 feet. This one however is not running a long distance and the probe and wire are wired directly to the BCS without any extension wire.

My second question is if anyone has a good way of programing this BCS for heating and cooling with a fridge and a heating element. I have tried with hysteresis control but I am worried about over cycling my fridges compressor. I know some controllers out there have a way to program a delay from 1 to 10 min so temperature swings do not over cycle the compressor. Any ideas would be most appreciated.

Thanks in advanced for any help.
gthielen
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Location: San Clemente, CA

Re: Fermentation Temperature control with fridge and fermwra

Post by gthielen »

Hey Trevor,

I know this post is pretty old, but I just joined the forum and have almost the exact setup. I don't know about your temperature reading problem, but I created a process to include a compressor delay like what you described.

Basically you define four states all with direct output control:
- Off (output 1 and 2 off)
- Heat (output 1 on, output 2 off)
- Cool (output 1 off, output 2 on)
- Cool Delay (output 1 and 2 off)

For the Off state, its exits are:
- Temp <= your desired temp - differential goto Heat state
- Temp >= your desired temp + differential goto Cool Delay state
Also set a countdown timer for your desired compressor delay value (I use 5 minutes)

For the Heat state, its only exit is Temp >= desired temp goto Off state
For the Cool state, its only exit is Temp <= desired temp goto Off state

For the Cool delay state, define the same timer as in the Off state as "Continued from previous state", and create its exit as Timer <= 0 goto Cool state.

When the Off state is entered, the compressor delay timer starts counting down. If the Cool condition is met, it drops into the Cool Delay state until the timer expires. It will then enter the Cool state to check the temperature and start the cooling cycle. If the temp is already cool enough, the state exits immediately to Off and restarts the timer.

The only downside of this is that if the unit was in Heat state and exited to Off state, the timer will start again even though the compressor wasn't on. This probably isn't a big deal when dealing with a fermenter though. I was thinking of looking into addressing this with registers or ladder logic, but it's working pretty well for now.

Incidentally, which SSRs did you use, and how hot do they get?

Cheers!
kwhizr
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Joined: Fri Jun 19, 2015 6:38 am
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Re: Fermentation Temperature control with fridge and fermwra

Post by kwhizr »

I don't know who may read this (#hello? #noteinabottle)

But I thought I'd add a note to this thread. I recently set up a BCS-462 system for eHERMS brewing, and shortly thereafter, my Brewpi side by side fermentation chamber went out. I decided to incorporate the BCS into my fermentation setup by running some Cat5 lines over to it. I have SSRs controlling the damper control and some outlets set up for fermwrap heaters.

After reading this thread, I've set up my fermenter process similar to the setup described above, and then in further reading, found a mention of a switchable "cold crash" process from JonW. So I'm adding a Cold Crash state to mine - with it's exit point being the desired temp OR the cold crash "switch" being off. It then transfers to the OFF state. I've also modified the Off state to include the cold crash "switch" so if it detects it as "on" it will send it to that state.

One change from the one above - which has yet to play out fully - I've changed the cool delay function so that it's the default first stop from the OFF state if the temp is too high. Once the timer reaches '0' it will then go to "cool" or "cold crash" if that toggle is flipped before the timer runs out.

I'm using the Direct On / Off for the compressor controls and the hysteresis mode for my fermwraps.

I can't say enough for the all the hard work everyone does on this forum - Thanks guys.
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