I do cringe at the phrase wiring centre, in the main they are just a junction box, why give them a different name? But central heating wiring as said should come from one supply, so in an emergency that supply can be replaced, mine will run from the solar inverter and battery should the DNO supply fail, and with some boilers if the supply is not taken from the boiler, it is easy to by-pass the boilers overload device.
My boiler is supplied from a fused connection unit (FCU) not really a good idea, better with a plug and socket, so I can power from an alternative supply
like shown which can give 300 watt, but since connected to my 6.4 kWh battery and 5 kW inverter for me, it does not matter.
Where we have multi-cables between points, I suppose only one needs to carry the earth,
I am changing the trigger for my boiler from a timer to a wiring centre.
That I don't really understand, wiring centres are only junction boxes, I use a hub, in fact two hubs in parrellel which combine many control devices to the one boiler, so three thermostats, all of them programmable, so the time can change the temperture at which they are trigger the motorised valve, pump, and boiler.
Some connections are wireless, and some wired, due to the wireless I can mount the hubs above the boiler. It depends on the make and model used, with some the hub and thermostat are combined, that would not work for me.
Some programmable thermostats use extra low voltage, one of mine does, the Nest Gen 3 wall thermostat uses a 12 volt DC link to the hub, that could use two core cable, as it does not need an earth. It is called SELV which stands for sepreated extra low voltage, and sepreated means I can't connect an earth.
I do wonder if the wiring centre you talk about is really a hub?
