Yeah, hysteresis control aka "bang bang" control can also be unreasonably effective.
It's a natural choice when your furnace can't throttle, or can but operates most efficiently at one output level anyway.
Since the system always pushes as hard as it can, it automatically reaches the setpoint in the minimum possible time. It's almost like a PID controller with infinite gain. But the tradeoff is jitter -- all the error gets pushed up to the highest frequency bands. As long as you don't care about that in your system, it's a great choice and effortless to tune.
It can also be a bad choice if there's any cost to changing or toggling the output, like if your furnace wears out from switching on and off a lot.
Many hot water circulating heating systems use bang-bang for the call-for-heat actuation but vary the circulating water temperatures in response to the outdoor temperature (via an “outdoor reset” input to the system).
Properly set, this dampens the swings of temperature in the rooms as the heat gain is more closely matched to the heat loss, increasing comfort and economy of the system.
It's a natural choice when your furnace can't throttle, or can but operates most efficiently at one output level anyway.
Since the system always pushes as hard as it can, it automatically reaches the setpoint in the minimum possible time. It's almost like a PID controller with infinite gain. But the tradeoff is jitter -- all the error gets pushed up to the highest frequency bands. As long as you don't care about that in your system, it's a great choice and effortless to tune.
It can also be a bad choice if there's any cost to changing or toggling the output, like if your furnace wears out from switching on and off a lot.