Are 30mA split load consumer units non compliant under 18th edition

[stefanli69]

Hi All,

Just wanted to see what peoples opinion is

is installing a 30ma Split load board compliant/ non compliant under the 18th Edition or you have to use RCBO's for each final circuit?

BS7671:2018, Page 155 regulation 531.3.5.2 is a note which says on TN systems which states " Exept where particular restrictions on selectivity applies; Several circuits may be protected by the same device"

Views?

 

[JBW175]

RCBO's are a nice to have if you can afford them and give you greater control over each circuit, split load boards are compliant though.

 

[Spoon]

It all depends on your interpretation of the regs.
IMO, Yes they are compliant.
This was discussed in another thread where some members said that they are not compliant.
I will see if I can find it.

 

[westward10]

Hi All,

Just wanted to see what peoples opinion is

is installing a 30ma Split load board compliant/ non compliant under the 18th Edition or you have to use RCBO's for each final circuit?

BS7671:2018, Page 155 regulation 531.3.5.2 is a note which says on TN systems which states " Exept where particular restrictions on selectivity applies; Several circuits may be protected by the same device"

Views?

Your last paragraph gives you the answer. This is new to the 18th Ed.

 

[APE37]

I believe they are still compliant. However, in the regs, it does state selectivity and also there is another reg that says you shouldn’t exceed 30% of the rcd tripping current, which I believe is around 9ma. So I believe it is preferable to use individual rcbo as it reduces the amount of leakage current on a circuit and makes more of an easy installation. But if you can calculate how much earth leakage is in a group of circuits there is nothing wrong with using a dual rcd unit. That is my opinion anyway.

 

[Andy78]

There is also the new reg that states that RCDs must have overcurrent protection if the upstream fuse does not offer this and the total rating of the devices protected by the RCD exceeds the rating of the RCD.
Easier to use RCBOs all round and offers a better installation for the customer and for future work.

 

[telectrix]

There is also the new reg that states that RCDs must have overcurrent protection if the upstream fuse does not offer this and the total rating of the devices protected by the RCD exceeds the rating of the RCD.
Easier to use RCBOs all round and offers a better installation for the customer and for future work.

so a RCD protects 4 circuits (as normal in a dual RCD board), 1 32A cooker, 1 32A sockets, 1 6A lights, 1 16A c/h. total rating of MCBs 86A. RCD rating 80A. so not compliant. however those circuits will not draw anywhere near 80A as long as the sun shines. has the world IET gone mad?

 

[Andy78]

so a RCD protects 4 circuits (as normal in a dual RCD board), 1 32A cooker, 1 32A sockets, 1 6A lights, 1 16A c/h. total rating of MCBs 86A. RCD rating 80A. so not compliant. however those circuits will not draw anywhere near 80A as long as the sun shines. has the world IET gone mad?

According to new regs that arrangement would be compliant if backed up by a 60A or 80A DNO fuse or <80A OCPD of another type. Diversity is allowed to be applied to this if the RCD manufacturer allows, but none will.

Hager responded to this by changing all their dual RCD boards to 100A RCDs to make it a no brainer.

 

[Dustydazzler]

Once rcbo are £10 each then dual rcd spilt boards should be made obsolete imo

 

[JBW175]

Once rcbo are £10 each then dual rcd spilt boards should be made obsolete imo

i agree, at present though they're just too expensive for joe public to afford.

 

[Andy78]

i agree, at present though they're just too expensive for joe public to afford.

Many electricians have been installing RCBO consumer units for many years. I personally have not installed a dual RCD board for a few years now.
There are many affordable options available.

 

[richy3333]

Joe public shouldn’t be driving or steering our industry. If contractors are telling customers it must be RCBO’s for the correct reasons things would change.

 

[Dustydazzler]

Price will always steer the industry

 

[ferg]

I mostly still fit dual RCD boards in domestic.
Hager now use 100 A RCD's so it is compliant.

10 Hager RBO's would mostly make my customers turn white.

There are cheaper ones out there but none of my wholesalers stock them.

 

[Deleted account]

Good question.

A really easy safe answer would be to say yes they are still compliant, but RCBO boards are better.

Not so safe answer.

Ifeel split boards are now virtually obsolete and feel with the regulations now encouraging us to take into account disruption in the event of a fault splitting an installation between 2 RCD’s it possibly not so good design especially with the average domestic house having 8 separate circuits these days.

 

[Pretty Mouth]

The IET seem to think they are compliant, as they are suggested as a method of providing RCD protection within installations on p36 of the OSG

 

[MJPD29]

Rcbos are better but absolutely nothing wrong with installing split board

 

[Dustydazzler]

If you could fit an rcbo board for just a fraction more money than a split rcd board then why on earth would anyone fit the rcd board.
an rcbo board or better in every way thinkable

 

[ferg]

If you could fit an rcbo board for just a fraction more money than a split rcd board then why on earth would anyone fit the rcd board.
an rcbo board or better in every way thinkable

It's only a fraction more if you use lewden or the like.

How often are you expecting the RCD to trip in a normal domestic?

 

[Deleted account]

How often are you expecting the RCD to trip in a normal domestic?

very rarely, but when it happens the disruption to loosing half the houses electrics is why RCD split board is a poor choice.