4mm cable into the bottom of main switch.

[Steve93]

Eicr today had a 4mm T+E connected into the bottom of a main switch which went to a separate dB with 1 20amp rcbo. Then swa to a hot tub. That part is fine. What I’m unsure about is the reg I can say that the cables are not ok in the bottom of the main switch. The other dB is only about a ft away from the main one. What’s people’s thoughts on this? I know it’s rough as you like!!

 

[Charlie_]

Under fault conditions what is the maximum current/time a 4mm t+e can withstand?
What size fuse is protecting the 4mm cable from L to N & L to E faults?

 

[Lucien Nunes]

you can't rely on the 20a rcbo to protect the 4mm. What I mean by this is, future alterations,

It is not necessary or possible to protect an installation against incorrect future modifications. All systems can be modified so that they become dangerous.

It's the same as having a 1.5mm t+e for a lighting circuit protected by a 45a but at fused down to 6a at the first luminaire.

Not quite the same. Top of head without checking the numbers, think the 1.0mm² CPC would not be protected against fault current by a 45A fuse, whereas I think the 4mm² is protected by the cutout as would be any other tails if the CPC is 4mm² too, but if it's T+E, would have to look it up, sounds doubtful as mentioned above.

But the crux is 433.2.2 which allows OPD to be located somewhere other than at the source of the circuit, so long as certain criteria are met to reduce the probability of a fault on the circuit up to where the OPD is. It may be the case there that those criteria are met, whereas I don't think they would be on your hypothetical lighting circuit.

E2A:

What do you mean by in the bottom of the main switch.

what goes into the top?

Agreed, we should refer to supply side and load side. Those of us who spend most of our time with TP+N DB's are used to putting the supply into the botttom of the switch.

 

[Charlie_]

I would just code it badgers arse

How useful would that be if that was an actual code..
So many times I have seen horrific looking installations that still comply

 

[Wilko]

Hi - in order to make use of 433.2.2 as they’ve done I think they need to install the cable with specific protection against impact (say in metal conduit). Which I’m guessing won’t have been done. Reg 433.2.2 refers us to 434 and then 434.2.1 (ii) .

 

[westward10]

If the enclosure it supplies is metal the cpc must be able to withstand fault current.

 

[Wilko]

If the enclosure it supplies is metal the cpc must be able to withstand fault current.

Agree, I didn’t want to be tooo presumptive but even a 63A fuse will need more than 1.5mm ...

 

[SparkyAndGeorge]

Code 3

 

[Deleted member 26818]

Hi - in order to make use of 433.2.2 as they’ve done I think they need to install the cable with specific protection against impact (say in metal conduit). Which I’m guessing won’t have been done. Reg 433.2.2 refers us to 434 and then 434.2.1 (ii) .

That is not the case.
Generally tails are not contained in conduit, the mechanical protection is provided by the sheath.
Hence why we no longer allow unsheathed tails.

 

[Dustydazzler]

Code Red

 

[snowhead]

Code Red Brown

I've Harmonised that for you.

 

[stevels4]

I've Harmonised that for you.

My pet hate.....Colour Harmonisation!
3 phase meter change...all grey apart from L3 load which was brown....it was grey when it was finished!
Strange thing is on CT metering all the CT wires and the sense voltage wires are red!

 

[Deleted member 9648]

My pet hate.....Colour Harmonisation!
3 phase meter change...all grey apart from L3 load which was brown....it was grey when it was finished!
Strange thing is on CT metering all the CT wires and the sense voltage wires are red!

Couldn't agree more. Done a TPN board change a couple of weeks ago, half the blacks neutral, half phase......same with the blues. Despite the passage of time I still struggle to see how a panel of (allegedly) intelligent techies spent weeks debating it and came to the conclusion that was a good idea.

 

[gazdkw82]

The circuit originates from the OCPD (main switch), not the 20a rcbo.

It's a little frustrating because it's one of those grey areas like multiple spurs from 1 single point and not confirming r1+r2 on minor works etc. There is no real documentation clearly outlining it's not right but we all know it's a Badgers arse

 

[Wilko]

We could come up with a few of our own classifications, like they’ve got for films - RABA in this case .

 

[Marcus Vaughan]

The circuit originates from the OCPD (main switch), not the 20a rcbo,

Sounds like you are inferring that a main switch and OCPD are one and the same?