Installing dual RCD boards 18th edition

[Kahil1987]

Hi sorry in advance if this is a silly question but I was recently told by a friend who is an electrician also that dual RCD boards are no longer acceptable according to the new 18th edition hence why they've become cheap to buy. I understand that RCD protection is a must and RCBO is the best option when installing a new fuseboard. But I didn't know that dual RCD boards are not accepted for new installations and I couldn't seem to find it in the regs book either. Please can someone clarify this as it is cheaper to buy dual RCD boards for customers who are trying to save a few pounds. Thanks again

 

[MJPD29]

It is absolutely 100% acceptable to fit dual RCD boards. Ask your friend to point to the exact regulation that states otherwise. Offer both RCD and RCBO options to customers along with pros and cons and let them make the decision for themselves, sometimes people just don't have the budget for RCBOs which is absolutely fine.

 

[telectrix]

nothing in the regs. prohibiting dual RCD boards.

 

[IAmSparkytus!]

Not too sure if this is the case but surely electrical wholesalers wouldn't be allowed to sell anything which didn't meet regulations?

Obviously not every product meets every regulation but if there was a regulation that went to the extent of saying "dual split boards aren't allowed in any application" would the wholesalers be entitled to still sell them?

 

[DPG]

Not too sure if this is the case but surely electrical wholesalers wouldn't be allowed to sell anything which didn't meet regulations?

Obviously not every product meets every regulation but if there was a regulation that went to the extent of saying "dual split boards aren't allowed in any application" would the wholesalers be entitled to still sell them?

Wholesalers will sell whatever they have until it runs out.

 

[nicebutdim]

Wholesalers will sell whatever they have until it runs out.

And would buy more if there was a prospect of continuing to sell them profitably.

 

[brianmoooore]

The regulation in question here is the recent one that requires the current rating of the RCD to be equal or greater than the sum of the ratings of the MCBs it supplies, if the rating of the RCD is less that that of the suppliers fuse. Normally applies to 63A rcds serving a row of MCBs, where two 32A MCBs alone takes it over the limit.

 

[IAmSparkytus!]

The regulation in question here is the recent one that requires the current rating of the RCD to be equal or greater than the sum of the ratings of the MCBs it supplies, if the rating of the RCD is less that that of the suppliers fuse. Normally applies to 63A rcds serving a row of MCBs, where two 32A MCBs alone takes it over the limit.

Whats the purpose of this? Sounds like it would be difficult to achieve.

In a house with a 60A supply fuse, one side of a dual split board would more often than not feed a ring main and a cooker and the other side would feed another ring main and potentially a shower.

I'm sure the RCDs in a lot of the dual boards are rated 63A so they'd be no good?

 

[westward10]

The rating of the rcd should be of equal rating or above that of the supply protective device so an 80A device is fine backed up by a 60A fuse. The 18th Ed introduced a Regulation whereby it is acceptable for a single rcd to protect several circuits, previous to this you could argue dual rcd boards were not compliant this is no longer the case. I don't have my Regs to hand to quote the Regulation.
The fact manufacturers still produce them indicates their acceptance and that Hager units now have two 100A rcds to ensure compliance.

 

[brianmoooore]

I'm sure the RCDs in a lot of the dual boards are rated 63A so they'd be no good?

The ones with 63A RCDs are the ones being sold off cheap.

 

[Dartlec]

There's also the Type A / Type AC RCD issue to take into account so there may well be a sell off of the older stock type in the next year or so.

The rating of the rcd should be of equal rating or above that of the supply protective device so an 80A device is fine backed up by a 60A fuse. The 18th Ed introduced a Regulation whereby it is acceptable for a single rcd to protect several circuits, previous to this you could argue dual rcd boards were not compliant this is no longer the case. I don't have my Regs to hand to quote the Regulation.
The fact manufacturers still produce them indicates their acceptance and that Hager units now have two 100A rcds to ensure compliance.

Overload Protection - Hager UK - https://hager.com/uk/support/regulations-18th-edition/overload-protection

Has some fairly good examples of how they interpret it.

Reg 536.4.202
.....

“However overload protection shall not solely be based on the use of diversity factors of the downstream circuits. To achieve overload protection of RCCBs or switches, the rated current of the OCPD shall be selected according to the manufacturers instructions”.

Is the bit in question.

So it's not quite as simple - I'd imagine if a manufacturer sold a ready populated board with a 40A and 32A breaker on a 63A RCD you'd have to assume that they consider it safe.

But 80A RCDs or 100A RCDs seem to be becoming the standard now, hence perhaps the cheaper deals on 63A ones.

 

[brianmoooore]

I have two DNO supplies, side by side. Each supply feeds two 60A Wylex switch/fuses with sub mains running to CUs in four properties.
There would be no problem at all in using dual 63A RCD boards in any of these properties, whatever MCBs are fitted.

 

[Dartlec]

I have two DNO supplies, side by side. Each supply feeds two 60A Wylex switch/fuses with sub mains running to CUs in four properties.
There would be no problem at all in using dual 63A RCD boards in any of these properties, whatever MCBs are fitted.

There are also lots of flats protected by 63A MCBs I've seen - which again would be fine, so still plenty of market for them....