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your cooling system sounds very interesting tbh, and i'd love it if you had pics or any explanation, even if yo point me towards a thread youve made about it if you have.
Happy to provide pics, thanks for asking. The overall system is below. If memory serves all of the parts less the fermenter cost under $150. There is a manually controlled heating pad strapped to the fermenter with velcro strips. It is controlled from the raspi via the hot relay. I drilled the lid of the fermenter for the thermowell on the left and the cooling coil on the right. A cheap 16 quart cooler has a couple of holes drilled for 3/8 tubing, duotight elbows to connect to the coil, duotight bulkhead fittings to fit to the lid. As you can see this is as sad fermenter, empty at the moment.
When I am fermenting, I button an old down vest around the fermenter, it is a perfect fit.
The thermowell and coil
A fish pond pump sits in the cooler, controlled by the raspi via the cold relay. a one wire temp probe sits in the water. The probes are typical of the kind you buy for raspi or Ardino. I swap frozen gel packs in and out of the water as needed.
The raspi controller manages both relays, has a web server so I can access via wifi to see the beer temp, water temp, target temp and the state of the relays. I can also set the target temp, so if I am ramping, I just have to bump the target temp up or down at the appropriate interval.