6mm² Cable to 6amp MCB and 1mm² cable..? :D

[eorpa]

Hello, doing some DIY electrics and quite capable but can't seem to find an answer on this point..I want to connect an LED cabinet light in the bathroom (Correct zone and perc rated etc..)

There was previously an electric shower, now replaced with a hot water system unit, so there is an unused cable and running into the bathroom area. However this is a 6mm² cable, I will replace the MCB with a 6amp in the CU but I want to connect the cabinet light to the power cable; can I connect a 2 core and earth cable to this gauge?

I will make the actual connection under the floor in the next room so there will be no connections in the restricted zones. Will also run the cable to the cabinet light through metal conduit under the bath (Or does it need to be under the floor?) to the wall and up a channel (Also in conduit) behind tiles to the light.

Does that seem like it would work? Advice appreciated
Thanks
Paul

 

[AndyPRK]

HOW ABOUT putting a FCU with 3A fuse where the 6mm ends and new cable starts.

But this can't be under the floor. Neither can a screwed junction

 

[JohnW2]

There was previously an electric shower, now replaced with a hot water system unit, so there is an unused cable and running into the bathroom area. However this is a 6mm² cable, I will replace the MCB with a 6amp in the CU but I want to connect the cabinet light to the power cable; can I connect a 2 core and earth cable to this gauge?

There is nothing wrong with having some of the cable far fatter than it need be. Some, maybe many, might argue that by changing the rating of the MCB and re-purposing the circuit, you would be creating a 'new circuit', hence notifiable.

I will make the actual connection under the floor in the next room so there will be no connections in the restricted zones.

If the connection is under the floor ('inaccessible'), it would have to be in a 'maintenance free' junction box - but I'm not aware of one which is designed to take 6mm² conductors.

Will also run the cable to the cabinet light through metal conduit under the bath (Or does it need to be under the floor?) to the wall and up a channel (Also in conduit) behind tiles to the light.

I'm not sure why you feel you need conduit under the bath. Will the cable run in the wall to the lights be in 'safe zones'? If so, then metal conduit would not be required (assuming there was RCD protection). Do I take it that the lights themselves are not within 'bathroom zones' (which would, again, make the work notifiable)?

The circuit will need RCD protection. Does that already exist in your CU?

Kind Regards, John

 

[eorpa]

The FCU sounds like great idea, I could put it on the wall outside the bathroom; would I be able to keep the larger MCB which was used for the shower if connected through this?

Good to know the cable gauge is not a concern, I have no issue with getting the wiring checked and notification through the appropriate authority, think I would need to do this anyway as the light is around 1.5 meters above the sink.

I don't have an RCD which is why i'm thinking the conduit would be necessary for the whole run, the channel up the wall to the light would be in a safe zone but behind tiles and in conduit.

(Maybe there is no way to please pedantic regulation in the current circumstances....)

Many thanks for your help
Paul

 

[JohnW2]

The FCU sounds like great idea, I could put it on the wall outside the bathroom; would I be able to keep the larger MCB which was used for the shower if connected through this?

Theoretically only if the MCB was 32A or less, although IMO it's really more a theoretical than 'real' issue!

Good to know the cable gauge is not a concern, I have no issue with getting the wiring checked and notification through the appropriate authority, think I would need to do this anyway as the light is around 1.5 meters above the sink.

Position relative to sink is not relevant. Is it within 600mm (horizontally) of a bath or shower, and is it more than 2.25m above floor level? However, as I said, some may regard what you propose as a (notifiable) 'new circuit'. Notification doesn't work as you imply. You either have to notify to the council yourself (which, with the worst LAs, could cost 'a few hundred pounds') of get a registered self-certifying electrician to do the work.

I don't have an RCD which is why i'm thinking the conduit would be necessary for the whole run, the channel up the wall to the light would be in a safe zone but behind tiles and in conduit.

Anything new in a bathroom requires RCD protection, regardless of what cables are buried and how they are protected.

Kind Regards, John

 

[AndyPRK]

instead of fitting an FCU, you could fit a fused RCD unit so solve that problem.

 

[EFLImpudence]

Theoretically only if the MCB was 32A or less, although IMO it's really more a theoretical than 'real' issue!

Which issue did you have in mind?

 

[JohnW2]

Theoretically only if the MCB was 32A or less, although IMO it's really more a theoretical than 'real' issue!

Which issue did you have in mind?

Not so much an issue as 'people' - those people (not including either of us) who apparently feel there is a problem in having an accessory 'rated' at 32A protected (upstream) by a OPD with In >32A, even when there is downstream 13A protection!

Kind Regards, John

 

[EFLImpudence]

 

[eorpa]

it's 2.1 meters above the floor and 30cm from the bath edge (Though several ft above)...the RCD instead of the FCU outside the bathroom seems to be a good idea, I can only seem to find 13A units though but presume I can change the fuse in it for a 3 or 6A, or will 13A be fine for a low voltage LED light, on the other hand, it isn't a perfect world..

It's sad that the regulations deter getting professionals in or checking with authorities as changing something (Even to make it safer) is opening a can of nazi worms!

 

[EFLImpudence]

I can change the fuse in it for a 3 or 6A, or will 13A be fine for a low voltage LED light, on the other hand,

Yes, that's how it's done.

it isn't a perfect world..

Indeed, but if they fitted 3A ones and you wanted 13A ...

It's sad that the regulations deter getting professionals in

They don't, it is far cheaper than notifying the LA.

or checking with authorities as changing something (Even to make it safer) is opening a can of nazi worms!

Only because you don't know how to do it - it depends what you mean by safer.

 

[JohnW2]

it's 2.1 meters above the floor and 30cm from the bath edge (Though several ft above)...

That's "Zone 2", and therefore notifiable, I'm afraid.

ithe RCD instead of the FCU outside the bathroom seems to be a good idea, I can only seem to find 13A units though but presume I can change the fuse in it for a 3 or 6A, or will 13A be fine for a low voltage LED light, on the other hand, it isn't a perfect world..

Yes, we're talking about an RCD FCU, and you can change the fuse in it to whatever you like - 3A would be more than adequate.

Kind Regards, John

 

[ban-all-sheds]

Hello, doing some DIY electrics and quite capable

The FCU sounds like great idea .. would I be able to keep the larger MCB which was used for the shower if connected through this?

 

[eorpa]

Quite capable doesn't mean to say I have the necessary knowledge for every situation, which is why I'm here getting advise from these helpful people

 

[ban-all-sheds]

The knowledge you didn't have is really pretty fundamental and basic.

Of course everybody has to learn everything they know, and not one person ever comes to know everything.

But the point I would like to make is that you seem to have an exaggerated opinion of your capability.