Other electrician replaced RCBO with MCB

[jumpjamesjump]

Was called out to a car park where they had the lighting circuit tripping out. Fixed the issue by putting damaged cables in an IP rated box. However just realised that the electrician who came out before myself took out the RCBO and replaced it with an MCB in hope that it would stop tripping, which it did, but only for a few hours. He said it's armoured cable and doesn't need an RCD. I'm pretty newly qualified and feel fairly unknowledgable lol, but here's my guess.

Being an existing installation as long as all the lights are all earthed I guess it's ok, but it wasn't originally done like this so I think it's just a straight up big fat no no, I think the client only got me in because their normal electrician couldn't make it so was hesitant to raise the issue straight away. The installation is a combination of black metal bollards and plastic brick lights. Just was wondering what you experienced guys thought before I start saying that the other electrician is wrong and the circuit is unsafe.

Thank you very much in advanced

 

[haptism]

Fixed the issue by putting damaged cables in an IP rated box

Is all the cabling in the circuit of SWA ? If not then the circuit would need rcd. What kind of damage is evident, to the equipment or the cabling. Are external CW glands being used for the armoured ??

 

[davesparks]

Is there anything in the circuit which requires RCD protection?

You say it's a carpark so presumably it's a commercial installation?
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Is all the cabling in the circuit of SWA ? If not then the circuit would need rcd. What kind of damage is evident, to the equipment or the cabling. Are external CW glands being used for the armoured ??

Why would the circuit not need RCD protection if installed in SWA?

 

[jumpjamesjump]

Is all the cabling in the circuit of SWA ? If not then the circuit would need rcd. What kind of damage is evident, to the equipment or the cabling. Are external CW glands being used for the armoured ??

No damage is evident after I fixed the run over bollard cabling. Yes they are.
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Is there anything in the circuit which requires RCD protection?

You say it's a carpark so presumably it's a commercial installation?
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Well the metal bollards, but they were installed before the 18th edition so strictly I thought they don't NEED an RCD.

Yeah I guess commercial, it's for about 20 domestic flats.

Think I'm just going to recommend having the RCD

 

[davesparks]

No damage is evident after I fixed the run over bollard cabling. Yes they are.
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Well the metal bollards, but they were installed before the 18th edition so strictly I thought they don't NEED an RCD.

Yeah I guess commercial, it's for about 20 domestic flats.

Think I'm just going to recommend having the RCD

Why would metal bollards require RCD protection? I'm not aware of any requirement in the 18th edition relating to bollards of any type?

On what grounds are you going to recommend RCD protection?

 

[haptism]

Why would the circuit not need RCD protection if installed in SWA?

Off the top of me head I was supposing that if the cable had earthed metallic protection then it didnt need rcd protection, unless it was feeding a socket (any type) then in that case it would.

 

[radiohead]

The point of whether the circuit requires RCD protection or not is irrelevant, the original electrician altered the fault protection to a circuit which clearly had a fault. That is not acceptable. If he/she had cleared the fault and then concluded that RCD protection was not required and could be omitted that would have been acceptable, assuming the regulations do not require it.

 

[littlespark]

I think the question here is, why was the rcbo used in the first place if it wasn’t needed?

Was the electrician who swapped it out for an mcb the same one who fitted it initially?

 

[Mike Johnson]

Just to give added protection?

 

[radiohead]

I think the question here is, why was the rcbo used in the first place if it wasn’t needed?

Was the electrician who swapped it out for an mcb the same one who fitted it initially?

I don't think that's the question at all, there's no reason why the car park lighting shouldn't have been on an RCD even if it was not required. If the circuit was healthy it woulnt have tripped. It seems likely that a circuit with a known fault was left with a fault and circuit protection reduced in order to prevent tripping, which then resulted in the mcb tripping. As the mcb would require a more considerable current to trip this proves that a major fault was present which testing would have picked up.
Once the fault was cleared there would no issue with replacing the RCBO with an mcb if it had been ascertained no additional protection was required.

 

[davesparks]

Off the top of me head I was supposing that if the cable had earthed metallic protection then it didnt need rcd protection, unless it was feeding a socket (any type) then in that case it would.

But why would a cable without earthed metallic protection need RCD protection?
A cable feeding a socket doesn't require RCD protection, the socket however probably does require RCD protection.

 

[stevethesparks]

But why would a cable without earthed metallic protection need RCD protection?
A cable feeding a socket doesn't require RCD protection, the socket however probably does require RCD protection.

It would all depend on installation method, and there will possibly be several methods along the route from supply to the end point.

 

[davesparks]

It would all depend on installation method, and there will possibly be several methods along the route from supply to the end point.

Yes, that's my point, a cable doesn't need RCD protection just because it isn't SWA. And there are situations where SWA would require RCD protection.

 

[Abacus614]

Wouldn't you say if you cant gaurantee the depth of which the cable is buried or confirm if it has added mechanical protection then an rcd be required? This may possibly been a suggestion following an EICR and the remedials suggested providing addition protection by RCD. Who knows, anyway.

We do loads of carpark lighting and normally a tripped circuit is almost down to a dodgy ballast. I'd suggest you strip down the circuit and do some insulation resistance tests to confirm the integrity of the cable.