Fault finding/RFC to radial

[gazdkw82]

Helped a friend out today, downstairs sockets randomly tripped during the night and now won't stay on. I narrowed it down to an earth fault on a leg between 2 sockets in the back room.

The cable dissapears under the floorboards and the room is laminated. I explained the situation and my friend was very against having to rip it out and replace it.

I suggested making 2x A2 radial circuits out of the RFC and making that leg redundant. Obviously that means 2x 20A MCB's to replace the 32A.

My friend was more than happy to do this, however it feels like a bodge and I'd be more happier to replace that leg.

Not really looking for advice, I guess I'm just sharing my experiences.

In this case, the customer (owner) of the installation has the end say on work, so long as it complies and is safe.

I did manage to do some checks on the circuit before leaving. Zs is good, RCD times are good and IRT were good.

 

[telectrix]

you do what you have to do within the limits of BS7671 and the customer's insistence if not damaging the property. think your solution was the only one in that case.

 

[Pete999]

Helped a friend out today, downstairs sockets randomly tripped during the night and now won't stay on. I narrowed it down to an earth fault on a leg between 2 sockets in the back room.

The cable dissapears under the floorboards and the room is laminated. I explained the situation and my friend was very against having to rip it out and replace it.

I suggested making 2x A2 radial circuits out of the RFC and making that leg redundant. Obviously that means 2x 20A MCB's to replace the 32A.

My friend was more than happy to do this, however it feels like a bodge and I'd be more happier to replace that leg.

Not really looking for advice, I guess I'm just sharing my experiences.

In this case, the customer (owner) of the installation has the end say on work, so long as it complies and is safe.

I did manage to do some checks on the circuit before leaving. Zs is good, RCD times are good and IRT were good.

If it's a RFC did you test R1+R2? or ring continuity end to end r1 r2 and rn? could be a fault in one of the socket outlet boxes testing first, changing circuits and omitting RFC legs as a last resort, not a good step in my book.

 

[SparkyChick]

The question is... do you issue an EIC (creating two new circuits - which would be notifiable) or issue a MEIWC (modifying an existing circuit - possibly one for each leg)?



And I agree with @telectrix . You can only do what the client will allow you to do so long as it complies with the regs. In this case if they're not up for lifting the floor, you've done what you can.

 

[gazdkw82]

If it's a RFC did you test R1+R2? or ring continuity end to end r1 r2 and rn? could be a fault in one of the socket outlet boxes testing first, changing circuits and omitting RFC legs as a last resort, not a good step in my book.

Yep. Confirmed RFC continuity. I agree Pete, it's not ideal but what are the options available?

I got >200Mohms on both legs from CU and 0.02Mohms line-earth on the leg in question

Making 2 radials out of a RFC circuit is not outside the scope of regs, so long as the circuits are suitably protected.

 

[gazdkw82]

The question is... do you issue an EIC (creating two new circuits - which would be notifiable) or issue a MEIWC (modifying an existing circuit - possibly one for each leg)?



And I agree with @telectrix . You can only do what the client will allow you to do so long as it complies with the regs. In this case if they're not up for lifting the floor, you've done what you can.

It's a new protective device so it's an EIC

 

[SparkyChick]

Yep. Confirmed RFC continuity. I agree Pete, it's not ideal but what are the options available?

I got >200Mohms on both legs from CU and 0.02Mohms line-earth on the leg in question

Making 2 radials out of a RFC circuit is not outside the scope of regs, so long as the circuits are suitably protected.

You've done the right thing. I've been in the exact same situation without the luxury of being able to add an MCB to the board (old board) so both legs are on one 15A MCB.

 

[Pete999]

Yep. Confirmed RFC continuity. I agree Pete, it's not ideal but what are the options available?

I got >200Mohms on both legs from CU and 0.02Mohms line-earth on the leg in question

Making 2 radials out of a RFC circuit is not outside the scope of regs, so long as the circuits are suitably protected.

OK have you investigated the leg in question for faults at the sockets? I guess all I'm saying Gaz is have you checked all the accessible connections?

 

[gazdkw82]

OK have you investigated the leg in question for faults at the sockets?

Faults at the socket? What do you mean Pete?

I've done an IRT on the leg disconnected on both sockets. 0.02Mohms. I did an R1+R2 on that leg, 0.04ohms.

The sockets themselves are fine because they both work as the ends of 2 radials.

 

[gazdkw82]

Sorry Pete, iv just read your adjusted post. You mean a fault at the point of connection to socket outlets?

I ended up disconnecting all sockets on the ring whilst going through fault finding.

The connections are good and the outlets are good.

 

[Pete999]

Faults at the socket? What do you mean Pete?

I've done an IRT on the leg disconnected on both sockets. 0.02Mohms. I did an R1+R2 on that leg, 0.04ohms.

The sockets themselves are fine because they both work as the ends of 2 radials.

Well you never actually mentioned you had done this and as an assumption I thought the leg in question may have a fault at a particular socket, so it's 2 sockets that are on one of the radials you propose, maybe this is where the confusion has arisen in my mind, never meant ti confuse you, but with a reading of 0.02 Meg on the two sockets, you can hardly energize that radial can you. Or have I got the situation horribly wrong in my mind? now I'll get back to watching Chuck Norris kick the s--t out of a Terrorist cell in Beirut.

 

[gazdkw82]

Sorry, I probably haven't explained it very well.

Both legs now >200Mohms

That leg between 2 sockets (the one that's now disconnected) is 0.02Mohms between line and earth.

I've tested both legs as separate circuits (Zs, RCD and IRT) and they are both good

 

[Pete999]

Sorry, I probably haven't explained it very well.

Both legs now >200Mohms

That leg between 2 sockets (the one that's now disconnected) is 0.02Mohms between line and earth.

I've tested both legs as separate circuits (Zs, RCD and IRT) and they are both good

Ah all is well apart from the 2 sockets, beginning to see what you have done sorry for being slow, it's an age thing, I reckon Tel is BSing his age as well.