At the risk of going over old ground Chrono-proportional is their attempt to use some of the control facilities long used in industrial process control into domestic environments.
A typical domestic heating system uses ON-OFF action.
Control of the floor temperature on the Warm-up brand of UFH is via time proportioned modulation i.e it takes a nominal time period of ,say, 10 minutes. It turns the heating element on for 2 minutes, off for 8, on for 2, etc to give 20% output. Another way to achieve this in electrical heating is phase angle modulation where the current is switched on for only a proportion of its cycle (of which there are 50 per second), clearly too short a period for gas boilers!
Integral action adds to (or subtracts from) the proportional action subject to the temperature error from set-point relative to the length of time the error has been present. It is not used in domestic controls, though I suspect it is integrated (no pun intended) into the control algorithms for some burner modulators judging by their tendancy to overshoot.
Derivative action works on the rate of change of error wrt time, again it's not used domestically.
Proportional action IS a great step forward in controlling domestic comfort levels, though chrono-proportional methods do seem rather crude when we all know a boiler PCB's life is just about limited to a certain number of boiler starts, and most modern ones have gas burner modulaton. Much better IMO to use the control outputs to alter the boiler flow temperature in response to demand, i.e 5 degC below set-point = 70 deg C flow temp; 1 deg C below = 60 deg C flow; 3 deg C above set-point = 50 deg C etc..
There are the rudiments of such a development on the Keston C40 where the CH and HW demands have seperate flow temperatures (not 2-step control), so they are almost ready to have the front panel knob replaced by an external contol signal. External signals from ext. air sensors, or even Michael Fish forecasts can obviously become integrated, but there is still the challenge of making the customer feel in control! (There is a heating system in a foreign ambassador's residence in London that is controlled remotely from the Motherland
)
Domestic controls still have a long way to go to even approach those commonplace in industry, the technology is there, the challenge is to make it desireable by the user and maintainable by the plumbers and heating technicians in the field. (
Engineers will be fully conversant with PID (3-term) control already). Control Engineering is a seperate subject in its own right, using lots of crazy maths and squiggly symbols, it'll get more and more into boilers so get ready to embrace it.
lots of love and hugs.....MM