First ever RCD trip

[Vicario]

I had a new CU installed in 2021 - dual RCD. This morning I was using the toaster and the RCD tripped, taking out several circuits including the downstairs ring. I have two questions as this is all new to me.

How easy would it be to split the downstairs ring so that the kitchen and living areas downstairs were on separate sides of the CU? Would a new ring need to be installed? Things like the alarm box, router, digital phone etc. went off and took some time to reactivate.

I don't quite understand the physics behind why the toaster tripped the RCD. I have read several old posts on the forum saying that burnt bits and other debris in the toaster can cause this, but why? No fault in the toaster or wiring, so what exactly caused it? I did shake out quite a bit of stuff, plugged it back in and now it's fine.

Yes, I am sure that it was the RCD that tripped (not the breaker) and yes, I did have an EICR before the CU was installed.

 

[flameport]

burnt bits and other debris

Crumbs get stuck between the heating element and the metal case, the heat causes them to burn into conductive carbon, current flows where it shouldn't which the RCD detects.

Would a new ring need to be installed?

Unlikely.

Existing rings can be split into radials.
Dual RCD consumer units can be refitted with RCBOs.
There are various options.

 

[ericmark]

As @flameport I had two RCD's in last house, they seemed to have bouts of tripping, then few years before next trip.

The cost of RCBO's has dropped, around £15 each, varies make to make, but a freezer full of food will cost more than changing to RCBO's so this house all RCBO's.

However some consumer units allow a few RCBO's as well so you may be able to put critical circuits on RCBO's.

 

[Vicario]

I suppose that my house is a bit unusual in that the kitchen and the living area are both on the same breaker/RCD. Although the toaster issue was easy to sort out, the other things I mentioned took a while. One answer would be to separate the kitchen and living areas ring into two radials - is that a massive job?

 

[Taylortwocities]

One answer would be to separate the kitchen and living areas ring into two radials - is that a massive job?

Not a massive job but It would need to be done by a registered electrician because this would be notifiable work (creation of one, maybe two, new circuits).
The massive downside is that the maximum current on either circuit would be limited to probably 20amps, whereas the ring has a 32amp limit.