@owend @Alex-cr Thanks both for the instructions. Just what I was looking for. I already have a thermistor in the chamber and I'm runing 3.3.

I've been uprgrading my railcore and I was suprised how well it holds heat. 45c chamber with 75c bed temperature.

I was wondering if it was possible to setup a fan so that it cools a passively heated chamber when it goes above the target temperatures. I've enclosed my printer both to help with noise and to increase the chamber temperature for some filaments. However, it's too hot for printing PLA. I was wondering if there is a way to setup a fan control to cool the chamber. Inverse of a heater control.

I'm using a Duet Wifi + Duex 5