extractor fan wiring conventions

[nozspark]

Maybe we should lobby the cable manufacturers????

How often do you think 1.0mm^2 or 1.5mm^2 , 3C & E, is used for 3 phase work??

I would say that much more is used as L, SL & N!!

So why isn't it made this way??

 

[ColJack]

3C+E is for 2 way switch wiring..

 

[nozspark]

Not got my thinking head on!!

 

[ban-all-sheds]

3C+E is for 2 way switch wiring..

It has lots of other uses - not sure it's only meant for that.

 

[ColJack]

didn't say it was only for 2 way lights..

nozspark said

How often do you think 1.0mm^2 or 1.5mm^2 , 3C & E, is used for 3 phase work??

I would say that much more is used as L, SL & N!!

So why isn't it made this way??

I pointed out the major use for it, where it is preferable to be able to distinguish between conductors..

I suppose that 2 brown, 1 blue and earth would also work since you don't really need to distinguish between strappers and the cores have to be sleeved anyway.. it just doesn't abreviate easily like T+E or 3C+E..

 

[helix]

spare cores should never just be cut back.. they should be terminated into a terminal block.. and depending on the circumstances may be earthed to remove coupled voltages from them..

Questions regarding this.

1. Having now installed 3C+E from junction box under floor, to 3 pole isolator, then to fan location, if I (or more precisly, the Mrs ) wanted to have a pull cord fan instead of timed what should I do? Ideally I don't want to disconnect the switched live from the junction box to the 3 pole isolator as I am going to tile the floor and might at a later stage want to connect in a switched fan.

Can I connect the switched live between the isolator and the fan to earth on both ends, and leave the switched live from the junction box to isolator connected to the switch?

3. For the timer fan, the fan instructions state I need to use a double pole 3 amp fused spur, but I also need to use a 3 pole isolator. I can't see how this would be wired?

Thanks

 

[rebuke]

Firstly, you shouldn't have a junction box under the floor, unless you have access to it from e.g. a liftable panel (under normal floorboards under carpet etc is not OK, you mention tiling the floor, this would obviously also not be OK to have a junction box underneath). If this is in a bathroom or other special location, then your LABC shouldn't sign off on it like this (assuming you're in England or Wales and have notified them).

In the general case however, what I would do is simply terminate the switched live in a piece of terminal block at the fan end. I wouldn't bother linking it to earth.

 

[Adam_151]

If you want to change your timer fan for a untimed pullcrd model, then simply swap it over and terminate the switched live in a connector block inside the fan... job done

What the other poster was on about was that you shouldn't leave a spare core just floating loose, it should be terminated properly at both ends, and ideally if its redundant it should be connected to earth as good practice, nowt wrong with having a switched live present at an item that doesn't need it as long as its terminated properly

You really shouldn't have an inaccesable joint box though...

 

[helix]

thanks both.

I could move the junction box to under the floorboards where the bath is going to go. that way, it would be accessible via the removable bath panel and a loose floorboard.

The junction box has been there for years, would this still be an issue for the LABC when signing off the new work? I didn't put it there, just connected new cable to it.

What about the 3 pole isolator / fused spur issue?

 

[Spark123]

Under the bath doesn't strike me as a good place to have a JB!

You can get away with using the fused spur to power the lights as well as the fan, and then the 3pole isolator to the isolate the L, SWL and N to the fan.
Is this circuit already RCD protected?

 

[helix]

The whole lighting circuit will be on an RCD. Adding a fused spur to bathroom lights and fan is not ideal, but if the only solution then so be it.