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Not sure if it's in any way practical, or better than other methods. I just wanted to test the idea, and didn't see it posted here already (sorry if I missed one). Working fine for my smallish factory, and should be easily scalable.
It's not a 100% off switch though, the first stage continuosly consumes hot water, keeping one boiler on. I guess that's the price for avoiding pointlessly moving items in a circle.

Also, my first post here. Hello all!