fixed wiring or flex?

[mackeral]

Recently installed an extractor fan. The installation instruction stated "Fan should be installed by fixed wiring only. A flexible cord should not be used."

Can anyone explain the reasoning for this and offer any other examples where fixed wiring is forbidden?

thanks as always

 

[andy]

fixed wiring is used for permanent installations. flex is used for portable. (you wouldnt wire a portable hoover with T+E, so why use flex for permanent wiring?)

 

[mackeral]

But a vacuum cleaner could still be wired with t/e and function the same.
Is the reasoning merely the mechanical differences of each cable type?
Not convinced yet...
So if the fan is 1 metre awayf rom its supply source what are the hazards of using flex as opposed to t/e?

 

[andy]

But a vacuum cleaner could still be wired with t/e and function the same.
Is the reasoning merely the mechanical differences of each cable type?
Not convinced yet...
So if the fan is 1 metre awayf rom its supply source what are the hazards of using flex as opposed to t/e?

i would have thought T+E is stronger and more mechanically protected than flex. as for the hoover. yes it could be wired and work, but the cable wouldnt last long. its designed for permanent installation. flex isint

 

[oilman]

....why use flex for permanent wiring?

Most boilers are fixed and the wiring is permanent, but it would be a right pain to wire it in T&E. T&E is just cheaper.

 

[SwindonSpark]

Blimey, whats the difficulty here?

Fixed appliances and outlets do not move, so T&E is suitable.

Flex.. (hmm.. say that again flex? - would that have ANYTHING to do with the word FLEXIBLE?).

Perhaps flex is used for vacuum cleaners because they move?

I know I'm being controversial here but maybe flex is suitable for appliances where there is a degree of movement but T&E is used where there isn't.

Hey since this is Christmas and I've been at the sherry, perhaps flexible cable is easier to move because it has a smaller cross sectional area. Wow there's a thought! Perhaps it's designed for a smaller current?

Nah! Don't worry folks, I've seen many installations where a "gifted" DIY expert has used flex in the walls and brought it back to the consumer unit.
Hey it it works for them, why not me? Well it does work for them but then so does the subsequent electrical fire!

 

[plugwash]

the reason flex is flexible is because it is made with a large strand count

you can get 2.5mm flex easilly and 4mm is availible so conductor area isn't an issue with flex for general perpose cuircuits.

the main issue i can see with using flex in something not designed for it is that its flexibility means that if something catches it it can easilly transfer that stress to the terminals (stuff designed for flex has cord grips to mitigate this issue)

the other potential issue is being unsable to tell what wiring is permanent and what wiring not

 

[SwindonSpark]

Good point plugwash.

So do you suggest that our chap here uses flex then?

 

[plugwash]

no T&E is the norm and the lower flexibility means it will tend stay in place reducing stress on the terminals if the cable is disturbed

using flex without some form of cord grip is generally a bad idea imo

 

[oilman]

Nah! Don't worry folks, I've seen many installations where a "gifted" DIY expert has used flex in the walls and brought it back to the consumer unit.

Hey it it works for them, why not me? Well it does work for them but then so does the subsequent electrical fire!

Er.......what subsequent fire? Why is flex with a given crossectional area any more likely to be a fire hazard than a similar area T&E cable? Provided the connections are terminated adequately.

 

[andy]

Nah! Don't worry folks, I've seen many installations where a "gifted" DIY expert has used flex in the walls and brought it back to the consumer unit.

Hey it it works for them, why not me? Well it does work for them but then so does the subsequent electrical fire!

Er.......what subsequent fire? Why is flex with a given crossectional area any more likely to be a fire hazard than a similar area T&E cable? Provided the connections are terminated adequately.

they have a lower power rzating. i.e 2.5mm T+E is rated at 27A. 2.5MM arctic cable is only rated at 20A

 

[AdamW]

I want to add a new bathroom to my property. Can I plumb the whole thing with a length of garden hose I happen to have handy?

For the sake of the £1 or so it will cost you to buy a piece of T&E to do the job properly, you might as well just do it properly. T&E is probably easier to run in such circumstances too. I have never tried fixed wiring with flex, but I would imagine it's flexibility and sheer dangliness makes it less easy to handle than good stiff T&E.

 

[kai]

Flex IS used for fixed wiring a lot.
Ceiling Rose to Bulb Holder
Wiring above Suspended Ceilings to Light Fittings
13amp FCU to Immersion heater
Switch to Storage Heater
Supply to Sink Waste disposal unit etc
The advantage is that the Earth core is not reduced in cross section
but Flex is more expensive, per metre than t+e cable of same rating.

 

[Damocles]

So it all comes down to the design of the fan. presumably it has no cord grip. Perhaps you could add one?

 

[paulh53]

the reason flex is flexible is because it is made with a large strand count

you can get 2.5mm flex easilly and 4mm is availible so conductor area isn't an issue with flex for general perpose cuircuits.

Have You Not Seen 25mm2 4 Core Flex?
I Have Used This Size "Flex" On Many Special Installations,

Go On "BAS" Have a Go