RCBO protection type, to settle a debate

[brucey2343]

Hi,

My QS believes an RCBO provides fault protection only, and we have to enter N/A on the test certs for the additional protection. Is this correct? We deal with TN-C-S and TN-S domestic. I assumed it provided both

Thanks!

 

[SparkyChick]

If it's a 30mA trip current then no, it is most definitely incorrect.

It provides fault protection via the MCB and additional protection via the RCD element, and of course earth fault protection where you are unable to achieve a sufficiently good Zs (typically TT systems).

 

[brucey2343]

So a 30ma RCBO does provide fault and additional protection? Is there somewhere this is in writing?

 

[ruston]

Have a look in definitions in BS7671. page 36.

 

[westward10]

What does he believe does provide additional protection if not a 30ma rcbo.

 

[ruston]

What does he believe does provide additional protection if not a 30ma rcbo.

It's a bit scary isn't it?

 

[brucey2343]

I am referring to the schedule of inspections, 4.19 "RCD(s) provided for additional protection/requirements - includes RCBOs (411.3.3; 415.1). 411.3.3 states additional protection must be provided for sockets not exceeding 32A and mobile equipment for outdoors not exceeding 32A (I assume this to be plug-in lawnmowers etc). So I am correct, 30mA RCBOs are both ticks on 4.18 and 4.19 of the inspections?

 

[ruston]

Yes if it has tripped within the required times.

 

[brucey2343]

This is supposed to be our boss...

 

[snowhead]

My QS believes

It's a bit scary isn't it?

Yes, very.

 

[westward10]

This is supposed to be our boss...

I would ask him/her what does provide additional protection.

 

[SparkyChick]

And what he believes an RCBO is.

And if he says combined MCB and RCD, then ask him why it doesn't provide additional protection is it has a 30mA trip current. Will be very interesting to hear his reasoning.

 

[PEG]

It's a bit scary isn't it?

I agree,but i would have gone for Quite Scary (QS)

Forgive me...it's blowing a gale out there,and i should be sticking a scaffold tower up,so,i'm feeling buoyant

 

[Pete999]

Hi,

My QS believes an RCBO provides fault protection only, and we have to enter N/A on the test certs for the additional protection. Is this correct? We deal with TN-C-S and TN-S domestic. I assumed it provided both

Thanks!

QS needs re educating

 

[Nigel]

It depends on what the purpose of the RCD is for. If it is for a high Zs then it is for fault protection but only if additional protection is not required. If it is for high Zs and for example sockets then it is still for both fault and additional protection.