RCD Rating

[coatesykid]

Can someone please explain to me how the Rating of RCD work because I've read on different forums that you can not exceed the rating of the RCD ie 63A or 80A if that's the case why do C.U like 10 way dual RCD, have a total MCB rating of 218 A if all MCB was used and only 143 total A for the RCD's, surly maximum demand comes into play.

 

[Silly Sausage]

Can someone please explain to me how the Rating of RCD work because I've read on different forums that you can not exceed the rating of the RCD ie 63A or 80A if that's the case why do C.U like this one

http://www.*************/p/volex-10-way-dual-rcd-split-load-consumer-unit-10-mcbs/54467?cm_mmc=GoogleBase-_-Datafeed-_-Electrical and Lighting-_-Volex 10-Way Dual RCD Split Load Consumer Unit %26 10 MCBs

have a total MCB rating of 218 A if all MCB was used surly maximum demand comes into play.

You'll get more sensible answers on DIYnot.com than here!

 

[coatesykid]

why is my question to basic

 

[Knobhead]

You try getting a 250A RCCD in a CU.
Use some common sense and diversity.

 

[plugsandsparks]

yep it is really, bit like asking why there are 10 - 13amp sockets in my house on a ring with a 32A MCB why does it not pop all the time

 

[plugsandsparks]

gets worse, my house only has a 63A fuse supplied by DNO, my shower, oven, kettle and microwave on their own take more than that - why has it not blown ?

 

[coatesykid]

so why are some sparks telling me I cant use maximum demand for RCD one guy was even telling me you can only have a maximum of 3 MCB of an RCD

 

[Silly Sausage]

why is my question to basic

OK...
the 63 or 80A ratings are the maximum in service current capacity of the device, more than that and they'll start warming up.
The crucial figure on a RCD is the mA value. RCDs are for additional protection to disconnect supply on the event of earth leakage faults.

 

[Knobhead]

This one could run and run.............

 

[plugsandsparks]

so why are some sparks telling me I cant use maximum demand for RCD one guy was even telling me you can only have a maximum of 3 MCB of an RCD

No idea, get the regs no off them and we will ponder their thoughts.

 

[coatesykid]

I know what an RCD does and I've always used maximum demand but when some called professionals have a completely different point of view to mine it makes me question what im doing obviously it would be impossible to protect an installation form earth fault if I didn't use maximum demand

 

[coatesykid]

is it ok to go off topic Ive got a question about earthing arrangements

 

[Silly Sausage]

so why are some sparks telling me I cant use maximum demand for RCD one guy was even telling me you can only have a maximum of 3 MCB of an RCD

Can you post a link to that piece of advice?

 

[Silly Sausage]

is it ok to go off topic Ive got a question about earthing arrangements

No, it's not!

 

[coatesykid]

Can you post a link to that piece of advice?

it was on a different forum

 

[Knobhead]

Post a link then, we’re intrigued.

 

[coatesykid]

cant remember which forum it was

 

[coatesykid]

Thanks for all the replies, I'm off to go post a new thread

 

[Knobhead]

Put a first class stamp on it. We can't wait.

 

[ackbarthestar]

Can someone please explain to me how the Rating of RCD work because I've read on different forums that you can not exceed the rating of the RCD ie 63A or 80A if that's the case why do C.U like 10 way dual RCD, have a total MCB rating of 218 A if all MCB was used and only 143 total A for the RCD's, surly maximum demand comes into play.

In the context of the question, you could think of an RCD as a main switch. Its rating of 63 or 80A is the maximum current that can flow via phase and neutral. The mA rating that follows is related to leakage or fault current that bypass the RCD.

As far as the maximum demand goes. No domestic installation runs at the maximum rating of its combined protective devices.