When we invested in a Brewtools F80 fermenter we needed a glycol chiller for it. As usual we decided to make one instead of buying one. The nice thing is that we have total control over the system and we could crank the BTU/h up to 8000 without breaking the bank.

Stripping the AC down to the bones

We bought a used AC on internet and started to strip away everything except the compressor, condenser coil, expansion valve and evaporator coil. All the electronics had to go as well and a Raspberry Pi running a custom Python program took its place.

Putting things together

We used 18 mm good quality fibre board shelfs for the casing. Kind of water tight and pretty sturdy.
The insulated box is an Dometic Cool Ice WCI 33, kind of expensive but crazy good insulated!

Firmware

The glycol chiller code is kind of simple, it runs the compressor when the glycol is over a set threshold and stops when the glycol is below the threshold. The condenser fan runs when the compressor is active and continue to run (at different speeds) depending on the compressor housing temperature.

The code for the circulation through the fermenter jacket is another story. We realized that almost 30L of -6C glycol pumped at 1200L/h is to much cooling effect even for 80L of liquid in the fermenter. We experimented a lot with different patterns for the pump and landed in a pulsed pump pattern where the “pump on time” depends on the temperature differens between target and actual mean temperature in the fermenter.

For measuring the temperature in the fermenter we use the standard bottom position AND a top sensor trough a modified lid of the F80.

The firmware advertise itself as an MQTT device and is integrated into Home Assistant (HASS) and the GUI for controlling and monitoring the fermenter is built in HASS.

There is also a ramping funktion built in so we have total control of the temperature ramp of the fermenter.

Things fermenter controller related