Light off socket circuit, which bit can be 1mm T&E?

[harrypotter]

Am I right in thinking the red should be 2.5mm, while the blue can be 1mm? Thanks.

 

[EFLImpudence]

No.

All 1mm² is fine.

 

[harrypotter]

No.

All 1mm² is fine.

Really? It's just that I've seen other stuff online that says everything up until the fuse should be 2.5mm. But I guess it does make sense that you can use 1mm for everything after the socket as that entire part is effectively limited to 3A.

 

[securespark]

I would say it's good practice to use the same size cable to feed the FCU then 1 milli on the load side.

Is there still a 1.5 rule for "power" cables?

Must get a copy of the latest book!

 

[bernardgreen]

The MCB ( fuse ) protecting the sockets is probably a 32 Amp device. Taking a circuit fused at 32 Amp into a ceiling rose rated at 6 Amp is not a good idea.

 

[harrypotter]

View attachment 351521

The MCB ( fuse ) protecting the sockets is probably a 32 Amp device. Taking a circuit fused at 32 Amp into a ceiling rose rated at 6 Amp is not a good idea.

Yes, I guess that's the proper way. It's on a 16A device, just a couple of garage sockets.

 

[EFLImpudence]

Really? It's just that I've seen other stuff online that says everything up until the fuse should be 2.5mm. But I guess it does make sense that you can use 1mm for everything after the socket as that entire part is effectively limited to 3A.

Yes exactly, well done.

The fuse does not have to be at the beginning of the cable being protected (as long as fault protection is adequate with another device).

 

[EFLImpudence]

I would say it's good practice to use the same size cable to feed the FCU then 1 milli on the load side.

Why are there regulations in place which allow you not to?

Is there still a 1.5 rule for "power" cables?

It's a light.

 

[EFLImpudence]

The MCB ( fuse ) protecting the sockets is probably a 32 Amp device. Taking a circuit fused at 32 Amp into a ceiling rose rated at 6 Amp is not a good idea.

Again, why do you think it is allowed.

 

[EFLImpudence]

The MCB ( fuse ) protecting the sockets is probably a 32 Amp device. Taking a circuit fused at 32 Amp into a ceiling rose rated at 6 Amp is not a good idea.

What about into a socket rated at 13 Amp?

 

[harrypotter]

Example video saying 2.5mm should go into fused switch...

But... the current going through that 2.5mm will be limited by whatever fuse is in there, even though the fuse is 'after' that wire. So if its a 3A fuse, I don't see why it can't be 1mm as @EFLImpudence is saying.

 

[Harry Bloomfield]

Nothing to prevent you wiring it all in 2.5mm, thus avoiding the need for it to be fused. That would avoid the need to buy two sizes of cable, and avoid the cost of a fuse. In fact, if the cable is clipped direct to a surface, along it's entire length, then 1.5mm T&E could be used from the socket, and again no need for the fuse - saving even more of the cost.

 

[securespark]

Why are there regulations in place which allow you not to?

When I install stuff, I try (you can't do it in every case) to make it future-proof.

It's a light.

But do the regs still disallow 1 milli to be used on "power" circuits?

 

[EFLImpudence]

When I install stuff, I try (you can't do it in every case) to make it future-proof.

Why; what is going to happen?

But do the regs still disallow 1 milli to be used on "power" circuits?

Did they ever?

 

[bernardgreen]

But... the current going through that 2.5mm will be limited by whatever fuse is in there, even though the fuse is 'after' that wire.

Think about faults.

If the 3 Amp fuse overheats and the FCU becomes a lump of conductive carbonised plastic then the 3 Amp fuse is no longer effective at limiting the current.