Here's a way to heat and/or cool a fermenter
All you need is hot or cold water from a faucet and a wort chiller.
As the name implies a "wort chiller" is mostly used for cooling.
It also works good for gently heating a fermenter.
Most people don't have hot enough water to raise the temp of wort that is worth using (hot water heater). You would also be expelling a lot of energy that way for little gain.
Why not just use steam from a boiler instead?
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I think it was SOCD that posted in a lg batch thread to heat a cooler with an aquarium heater, and circulate the water through a wort cooler and cycle the pump with a cheap stc-1000. Works great in my 60F basement.
A friend has his fermenter bucket in the shower
Since he has already used the chiller to cool the mash
He leaves it in the fermenter and uses it for a heater.
Personally, I like using a fermenter with an electric heated water jacket
The yeast likes it too, especially with the fermenter heated from the bottom and sides