Fermentation heater

[specialkayme]

@piojo - thank you for taking the time to describe this. You did a very good job. I have most of the misc. parts lying around (some wire, solder, shrink wrap wiring stuff, although I don't think the right size), but I don't have the resister or anything that it should be mounted on. I'm assuming this one would work well? https://www.amazon.com/dp/B07FS1249Y/?tag=skimlinks_replacement-20 Should I be looking to mount it on a heat sink, or something else?

It looks like it'll probably end up costing me $12-16 to build, and maybe an hour or two of time. I'm sure I'll learn something in the process, but I'm not sure it makes much sense when compared to a reptile heating pad or fermentation heater that costs $11-20. Or would you disagree?

 

[piojo]

@specialkayme I suggested gluing it to chopsticks (probably in a X pattern) to mount the resistor in air. If it's in a paint can or soup can, it doesn't need a heat sink, because the can is protection against touching. Mine has a heat sink+fan mostly because I originally used it in an application with no thermal mass, so if it built up heat inside, there would be a large temperature overshoot. You can always add it later, but I don't see any reason right now.

The load resistor you found is correct, but so is your assessment. Are you ever gonna make your own temperature controller with Arduino or Raspberry Pi? If so, you should use the load resistor because that technique is transferable (does not require using mains voltage). If this is the only heating system you build, you have my permission to buy a reptile pad.

Sometimes I choose to build rather than buy if I can get the final result faster or if the DIY thing will be customized in some useful way. In this case I don't see the advantage, unless you are near an electronics components store. In that case, the advantage would be that you could get the project finished as soon as you want.

 

[Aristoi]

Sounds like you were using a single stage temp controller? Or you did not have your mini fridge plugged into the cooling side of a dual stage controller? Or there was an issue with how you programmed the controller?

I use a 16W heat pad under my PET fermenters in a large-ish wine fridge, controlled by an Inkbird ITC-1000F, with the temp probe in a 12" thermowell through the lid. I don't have the problem you describe.

My experience is that the heat pad gives very gentle distributed heating. I have no fears of damaging the plastic fermenter or cooking the beer. Should the temp rise above my set point (+ offset), the controller will turn on the refrigerator. In cool weather all it does is cycle the heat pad. I have my chamber in a shop hallway that stays 50-60F in the cool months.View attachment 597499

i was using a 2 stage controller with the min temp tolerance (1F) on both heat and cool. Keep in mind the controller probe was in my brewbucket thermowell and that temp lagged the fermentation environment. So i am convinced the off flavors were from stratification in temps with the outer wall of the SS brewbucket until the probe in the thermowell reached set temp. This is why i downsized the 23w heater to 4w in the small fermentation environment of a mini fridge to provide gentler heat with the ambient sensor as added protection.

Maybe the difference is the your PET sidewall on your fermentor insulates from stratification better than SS, and i had a smaller fermentation environment plus i was using a 50% higher watt heater than yours.