EICR RCD 63A exceeded by breaker total code

[westward10]

If a 63a rated RCD gets a C3, then a lot , if not most, new populated boards supplied now would warrant a C3 the minute they are fitted.

I would say that if a board comes with 2 x 632 RCDs then that is as manufactured and attracts no code whatsoever. The 63a refers to the current that it can interrupt without being damaged, if it trips with say 100a flowing through it, it will more than likely get damaged and have to be replaced. But it would have done its job.

Thermal damage to any components in a CU, not just RCDs would require at least C2, so that’s not really relevant.

63A relates to it's continuous running duty in normal operation. It's breaking capacity will be considerably higher into KAs so switching a 100A load is not likely to cause any damage.

 

[loz2754]

You may well be right Ian, but my point is that if you purchase and fit a new populated board such as below, you would need to put down the RCDs as a departure from the reg's. I would say that they were manufactured to a BS and fitted as per manufacturer's instructions.
View attachment 64824
View attachment 64825

Not really. You would be able to purchase and install this board if the design of the installation permitted it to be installed in line with the said requirements for overcurrent protection of the RCDs.
Otherwise you would have to specify a different board for that particular installation.

 

[andyb]

63A relates to it's continuous running duty in normal operation. It's breaking capacity will be considerably higher into KAs so switching a 100A load is not likely to cause any damage.

Thanks for that clarification Westward, I suppose that a board with a 100a main switch and 2 x RCDs is designed for a fairly balanced load over the two RCDs. I don't think I'll be coding this anytime soon unless I think one of the RCDs is likely to have more than 63a running through it by design. I've never come across this, most of the domestic installations I test don't even have 50a as maximum demand.

 

[Ian1981]

I don’t think it is a departure from bs7671 as how are you achieving the same level as safety, it would be a blatant non compliance.

 

[andyb]

Not really. You would be able to purchase and install this board if the design of the installation permitted it to be installed in line with the said requirements for overcurrent protection of the RCDs.
Otherwise you would have to specify a different board for that particular installation.

True Loz but the OP was just adding up the ratings of the MCBs and the boards illustrated both come with MCBs totalling near or over 200a. So it would be impossible to satisfy the regs as being described here.

I take peoples point here but on PIRs I'll still use my judgement to determine whether I think it's okay for a particular installation.

 

[loz2754]

True Loz but the OP was just adding up the ratings of the MCBs and the boards illustrated both come with MCBs totalling near or over 200a. So it would be impossible to satisfy the regs as being described here.

I take peoples point here but on PIRs I'll still use my judgement to determine whether I think it's okay for a particular installation.

True thanks for pointing out the actual MCB ratings. I didn't look at that detail.
If course it still may comply - the main fuse could be 63 or 60 amps...