Why has RCD type changed in 18th edition?

spud1 · Jan 27, 2019

Does anyone know why RCDs have changed in type in the 18th. Someone told me it was some5hing to do with DC faults? What type were they and what are they now?

Thanks

Spud

Deleted member 26818 · Jan 27, 2019

Not aware that they’ve changed.
It could be something to do with some cease to work if some types of d.c. voltage are present.

Gavin John Hyde · Jan 27, 2019

this will explain it all RCDs and the 18th Edition - https://www.voltimum.co.uk/articles/rcds-and-18th-edition

when you think about the number of devices such as laptops, flat screen tvs, smart devices, the list is endless that take mains ac and via transformer down rate it to dc then the potential for faults that the usual rcds wouldnt detect is present. how dangerous it is remains to be seen.

spud1 · Jan 27, 2019

spinlondon said:
Not aware that they’ve changed.
It could be something to do with some cease to work if some types of d.c. voltage are present.

When I say changed in 18th I probably being a bit broad. Hager have changed their RCD type and assumed it was something to do with the 18th but prob isnt

Deleted member 26818 · Jan 27, 2019

Where an installation has solar panels or a car charger, there is a possibility of d.c. current leaking into the rest of the system.
Type A and AC RCDs will not work if the d.c. current is too high.
Type B RCDs are not affected by d.c. current.

spud1 · Jan 27, 2019

Gavin John Hyde said:
this will explain it all RCDs and the 18th Edition - https://www.voltimum.co.uk/articles/rcds-and-18th-edition

when you think about the number of devices such as laptops, flat screen tvs, smart devices, the list is endless that take mains ac and via transformer down rate it to dc then the potential for faults that the usual rcds wouldnt detect is present. how dangerous it is remains to be seen.

This looks great thank you very much !

Nebu1a · Jan 27, 2019

Also check out Beama THE RCD HANDBOOK. Gives a lot of information

AJshep · Jan 28, 2019

RCDs have not changed, however.
Hager have decided to use type A RCDs in their split load boards, as well as uprating them to 100amp.
According to Hager there were a few instances last year where AC RCDs were returned to Hager due to failing to trip. They determined it was because of a high number of DC power adapters/usb charging sockets on the circuit, which creates a higher earth leakage which can also affect RCD trip times. So now they ship with type A RCDs due to better capability/ selectivity across the board. There is nothing wrong with AC type RCDs in most cases though.
Your hear different story's from the folk down the wholesalers, though im sure and some mis-informed Hager reps might get confused.

Really its down to the designer to select what type of RCD is best.

bigspark17 · Jan 28, 2019

AJshep said:
RCDs have not changed, however.
Hager have decided to use type A RCDs in their split load boards, as well as uprating them to 100amp.
According to Hager there were a few instances last year where AC RCDs were returned to Hager due to failing to trip. They determined it was because of a high number of DC power adapters/usb charging sockets on the circuit, which creates a higher earth leakage which can also affect RCD trip times. So now they ship with type A RCDs due to better capability/ selectivity across the board. There is nothing wrong with AC type RCDs in most cases though.
Your hear different story's from the folk down the wholesalers, though im sure and some mis-informed Hager reps might get confused.

Really its down to the designer to select what type of RCD is best.

A supplier asked me about 100Amp rcds due to 18th edition, i told him i was unaware of this, which i am. Does it only apply to single upfront rcd on 100A supplies not split?

AJshep · Jan 28, 2019

bigspark17 said:
A supplier asked me about 100Amp rcds due to 18th edition, i told him i was unaware of this, which i am. Does it only apply to single upfront rcd on 100A supplies not split?

They up-rated the rating of the RCD to comply with a different regulation, I believe there is a thread on here discussing it more in depth.
Here you go...
RCD RATING VS. SERVICE FUSE RATING - https://www.electriciansforums.co.uk/threads/rcd-rating-vs-service-fuse-rating.171274/

Nebu1a · Jan 28, 2019

I dont think that the RCDs have to be rated 100amps. Schneider are currently doing a dual RCD board with 2no 80amp RCD (type A) and a SPD.

Ian1981 · Jan 28, 2019

bigspark17 said:
A supplier asked me about 100Amp rcds due to 18th edition, i told him i was unaware of this, which i am. Does it only apply to single upfront rcd on 100A supplies not split?