Borrowing a live

[Harry Bloomfield]

Just to play devil's advocate and further my own understanding, presumably there is nothing wrong from a wiring perspective with say a programmer being on one circuit and a thermostat being on another? Each device would be powered by the live on that circuit and returned to the consumer unit along the neutral of the same circuit. Be a poor design though not being able to turn off all the central heating devices with a single mcb. Although what about the immersion - that would likely be on a separate circuit. Hmmm....

The immersion heater, is an entirely separate circuit, to the boiler and it's controls. In a domestic environment, anyone working on the boiler, and it's controls, would expect a single point of isolation, for the entire unit and it's controls, with the exception, of the immersion heater.

In industry, control circuits are often much more complex, so there is often a variety of circuits, fed from differing supplies, within the same enclosure, but they should be well-marked as such.

 

[Murdochcat]

Just set the heating to continuous and use the room stats to control the heat / time

Job done

 

[flameport]

Each device would be powered by the live on that circuit and returned to the consumer unit along the neutral of the same circuit. Be a poor design though not being able to turn off all the central heating devices with a single mcb

Totally unacceptable, as isolating one of the supplies would leave the whole lot energised via the other one.

Immersion heater is a separate unrelated device.