I brew in a fermentation fridge and use a BrewPi to control the fermentation temperature. To get the most accurate control of beer temperature, I’ve been using stainless thermowells in my plastic fermenters. I was excited about the Fermentasaurus product (in particular the pressure fermenting capability), but noticed that it had no allowance for a thermowell. I reached out to the manufacturer and they came back with the following ideas:
- Strap the temperature probe to the outside of the vessel (their recommended method)
- Add another hole + grommet to the lid and use a thermowell (not recommended – but will work).
I questioned whether the second option would still allow me to ferment under pressure, and they came back saying that the pressure on the hole should be quite low and a grommet should be able to hold it. They highlighted that it was at my own risk though and that I should do a pressure test after fitting it.
So I pulled the trigger and drilled a hole in my lid next to the Gas post. A few notes here:
- I used a 13mm spade bit as the plastic of the lid is quite thick. The challenge is holding the lid still whilst you drill. I cleaned up the hole using a plastic reamer.
- I already had a 40CM stainless (9mm diameter) thermowell with a rounded bottom end (the pinched thermowells I’ve found tend to tear the grommets when you push them through). I got my 40cm thermowell from Beerbelly.
- The grommet I used was bigger (20mm OD/9mm ID) than a normal lid grommet (and thicker). I got it from Sydney Home Brew Supplies on eBay in a 10 pack. It was slightly tricky to get it into the hole, but once it was through, it sits very neatly (and tightly) around the thermowell, especially when mounted in the lid.
I pressure tested and have used for 5 brews since May 2017 with no leaks or loss of pressure. I’ve used for both normal (airlock) and pressure ferments.
The final results can be seen here: