extractor bathroom off shower circuit not light circuit

[sellers]

You could comply with the regs and wire straight from the shower in 1.5mm

or you could add an unswitched spur inbetween,

or just take off the lighting.

all of the above would require an isolator.

 

[Andy™]

You could comply with the regs and wire straight from the shower in 1.5mm

but if manufacturers instructions say it must be fused at something elss than the rating of the shower (highly likely), then it wont comply with the regs

 

[ianmacd]

I don't think a 6A MCB terminal is physically any different from a 40A or 50A MCB terminal yet we all seem able to ensure a correct termination and grip with 1.0mm, 1.5mm, 2.5mm, 6.0mm, 10.0mm conductors. Also the earth and neutral bar terminations all use the same size diameter hole and securing screw. Do you not think that providing any termination is big enough for the largest conductor size required, most competent electricians would be able to ensure their joints are mechanically and electrically sound? I would think the problem to be more the reverse, trying to put too large a cable into a small termination.Doc H.

All your examples are correct but miss the point. We are talking about 2 disporportionally sized cables. How will the smaller be gripped properly? The twist and insulation on a stranded cable will provide an 'ancor' point to stop the cable splaying out but nothing will prevent the smaller cable from ending up not properly secured (and liable to overheat).

MK for example list their high load switches as follows:

Terminal capacity, 45A Switches and CCUs:

​

4 x 4mm2

3 x 6mm2

​

1 x 16mm2

​

Terminal capacity, 32A Switch:

3 x 2.5mm2

​

2 x 4mm2

​

1 x 6mm2

That to me reads that you can (for example on the 45A switch have 4 up to 4mm cables OR 3 up to 6mm cables OR 1 up to 16mm. cable

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[quote name='Andy

 

[Sidewinder]

Right,

Manufacturers cable capacities are there to ensure you don't cut strands off.

There is NOTHING wrong with installing a shower unit say 10kW with a 45A pull switch in 10mm sq with a 40A mcb is there?

Not as far as I can remember from the brb, which I don't have around.

SO next, you can reduce the area of a conductor if you fit a protective device within 3m, if the conductors are within the same enclosure then this is no issue.

So IF you say had a 45A wall switch in a cupboard for the shower, remembering that this shower switch is not for emergency switching thus could be anywhere as long as it is reasonable.

Then you could mount 2 FCU's tightly adjacent to the 45A switch, thus all conductors would be enclosed in substantially the same enclosure

Therefore no circuit protection required for the reduced CSA within 3m we would be talking of around 0.05m.



So then you have 2 FCU

 

[NozSpark]

There's a reg about downstream protective devices in the BRB...

how else would you do the supplies from a bus bar chamber to a switch fuse?

 

[Evans Electric]

You have always been able to connect smaller tails to busbars , "within the enclosure" . The risk of a short circuit is virtually nil .

 

[ianmacd]

Busbars with multiple cable terminals are not the same as stuffing a 1.5mm cable in with a 10mm cable in the same terminal. How will the 1.5 be properly gripped? The answer is it can not be, not with differing sizes of conductors.