what RCD circuit is this wire on?

[Greenmantle]

I have two cables that are terminating in junction boxes in my airing cupboard
This was done back in 2005 when I had my hot water system changed to an unvented cylinder and I assumed that they were no longer required.
House is a 2000 build so wiring is pretty new.

How to I find what circuit these wires are on without going through each and every RCD in the house?
Is there some piece of kit that I can purchase and add to my "tools you wish you bought sooner" tool cabinet

I know its not the immersion circuit on my hot water tank since that is already wired in.
I have a plan to use new circuits that is why I ask.
Cheers

[Belle427]

You can get a volt stick which will give you visual and audible indication voltage is present but you still need to turn off breakers to identify which one its on.
A cheap multimeter will do similar if you know how to use one.

[OutInTheShed]

You could of course deliberately cause a fault and see what breaker trips.
If any.

If you have to ask, maybe we should be advising you to leave well alone?

[CorradoTDI]

What size cable are they and are they twin and earth?

[mikey_b]

It s possible they aren t on a circuit in the traditional sense, if for example they are redundant cables that were used to control heating valves. In that case, they would have been routed in some way between thermostat, heating control panel and the motorised valves, and were never connected to an actual circuit from the consumer unit.

Another option is a feed for an immersion heater, but unless the tank was moved, I would have thought they’d use the same feed for a new one.