RCBO’s and Supplementary bonding

[ETradesmen]

Just a thought guys in terms of RCBO’s and supplementary bonding.

Obviously supplementary bonding isn’t required as long as a 17th / 18th condition consumer unit is fitted (dual RCD protecting all circuits) but what if it’s a main switch only with individual RCBO’s?

What is stopping somebody from installing an MCB leaving users at risk under fault conditions?

As they’re forced to install an MCB on a dual RCD board the user is covered but what if they haven’t got an RCBO on the back of their motor instead installing an MCB on a main switch only consumer unit?

 

[newfutile]

Nothing to stop a mcb being installed but the installer should be aware that additional protection will be compromised,as would no (RCD) Residual Current Device to domestic lighting . If no exposed and extraneous conductive parts are simultaneously accessible I don’t see it’s a problem.

 

[DPG]

Just a thought guys in terms of RCBO’s and supplementary bonding.

Obviously supplementary bonding isn’t required as long as a 17th / 18th condition consumer unit is fitted (dual RCD protecting all circuits) but what if it’s a main switch only with individual RCBO’s?

What is stopping somebody from installing an MCB leaving users at risk under fault conditions?

As they’re forced to install an MCB on a dual RCD board the user is covered but what if they haven’t got an RCBO on the back of their motor instead installing an MCB on a main switch only consumer unit?

Nothing you can do about it. If someone is going to fit an MCB because they don't happen to have an RCBO then there's no hope!

You might as well say you won't fit an FCU because someone might change the 3A fuse for a 13A one

 

[loz2754]

It's not possible to plan for every "what if" scenario. Anyone competent enough to change an MCB/RCBO etc, ought to be also competent enough to not make a change that will compromise safety.

 

[timhoward]

Obviously supplementary bonding isn’t required as long as a 17th / 18th condition consumer unit is fitted (dual RCD protecting all circuits) but what if it’s a main switch only with individual RCBO’s?

I'm all for short and simple explanations of regs but that is simplifying things a little bit too far!
That is only 1 of 3 requirements in order to omit supplementary bonding in a room containing a bath or shower. I'm sure you know this already but trainees read this forum too.

What is stopping somebody from installing an MCB leaving users at risk under fault conditions?

Bottom line is that good electricians take the time to understand the whole installation including the supply before modifying a part of it. There will always be some that won't. We can only live in hope that an EICR by someone more knowledgeable takes place before any harm comes of it.

I've previously found a RCBO board on a TT system where the heat source pump people chucked an MCB in it, thus meaning their sub-main, CU and the gear they installed had no fault protection.

but what if they haven’t got an RCBO on the back of their motor instead installing an MCB on a main switch only consumer unit?

No one is forced to fit the wrong device in a consumer unit. I have no shame in saying that I haven't got the right part and I'll have to return. It's a right pain sometimes, especially if you try and plan ahead and take what you need and it doesn't work out, but it's a reality of our job!

You might as well say you won't fit an FCU because someone might change the 3A fuse for a 13A one

I've unwittingly done the opposite once - I was half way home when I remembered the 3A fuses were still in my pocket after buying them at lunchtime and realising I'd not put one of them in the FCU for the extractor.....!

 

[mainline]

I've previously found a RCBO board on a TT system where the heat source pump people chucked an MCB in it, thus meaning their sub-main, CU and the gear they installed had no fault protection.

I would think it would help in the event of a L to N fault though