wrong cables???

[Rad1o]

We are just having an extension wired and the electrician has "told me off".

In the past I have moved light switches, put 2-way wiring into walls and also exteded our sockets.
For this I have used flex cable of proper diameter.

The electrician said I could not use flex cable in walls and floors.

Did I get him wrong?

Can someone explain to me in simple terms why this should be illegal.

I hate handling this mega stiff grey cable!!!
Flex is so much nicer to work with.

 

[Iggifer]

Absolutely nothing wrong with using flex for fixed wiring.

T+E / 3C+E is just much more common.

Assuming, as you say, the flex is of an appropriate diameter, has a CPC and terminated correctly at junctions it's fine. With the two way switching have you mixed solid core cable and flex in one terminal?

 

[EFLImpudence]

As long as the rating of the cable is suitable for the current there is nothing 'forbidden' about what you have done, assuming you have done it properly with regard to routing etc.

Having said that, it is not wise to have solid and stranded cores in the same terminal.

 

[PrenticeBoyofDerry]

I concur with the above replies.
Nothing in the regulations preventing the use of flex in hardwiring installations, providing the correct provisions are taken with accordance to BS7671, these being:
*Correctly rated for both voltage and current
*They are of the heavy duty type, unless the risk of damage during installation and service, due to impact or other mechanical stresses, is low or minimized or protection against mechanical damage is provided.(requirement 521.9.1)

 

[JohnD]

You will not find flex of "proper diameter" for sockets in the high street, and it is mostly too small for lighting circuits

What size did you use?

 

[Rad1o]

I have bought mine on the role from screwfix.

I used 2.5mm for sockets and a 500 W outside light. The other lighting cables are 1.5mm.
I would have connected a flex cable onto an old grey 2 core + earth.

No electric fires yet.

 

[JohnW2]

You will not find flex of "proper diameter" for sockets in the high street, and it is mostly too small for lighting circuits

Good point - but in this day and age, I suppose one has to reconsider one's definition of 'the high street'. Screwfix, for one, sell 1.0, 1.5 and 2.5 mm² 3-core and 1.0 mm² 4-core cable - and they have a branch very close to my local high street, even if one doesn't order on-line! It's only really when one gets onto cooker and shower circuits that finding suitable flex might be rather difficult.

Although very rarely used, I don't really see any particular problem with flexible cable, so long as it is either not 'exposed' or is 'heavy duty' - and, as the OP implied, working inside back boxes would be appreciably nicer (and hence probably less likely to 'go wrong') with flex. Does anyone know whether flexible cable (other than singles) for fixed wiring is common anywhere in the world?

Kind Regards, John

 

[SaladFingers]

Ask your electrician for a regulation number which states that flex cannot be used.

 

[Iggifer]

working inside back boxes would be appreciably nicer (and hence probably less likely to 'go wrong') with flex

It's so, so, so much nicer wiring sockets in flex than solid T+E, and to an extent, singles are nicer too.

It's so much easier to dress flex nicely, and to be fair, you can leave a lot more in the box should you need to reterminate at a later date.

I did a first fix of some 13a sockets for a friend in flex and I left him about 15cm of cores in the metal clad box, I could have left more but clearly he wouldn't need even that much, but there was still plenty of space

 

[PrenticeBoyofDerry]

I have bought mine on the role from screwfix.
I used 2.5mm for sockets and a 500 W outside light. The other lighting cables are 1.5mm.
I would have connected a flex cable onto an old grey 2 core + earth.

What you must consider that the current rating of flex and twin&earth cables of the same CSA, are different.
I would normally expect 1.0 flex to be rated at no more than 10A V 16A for T&E and 2.5 flex at 25A v 27A for T&E.
I doubt that it is an issue but worth checking your device ratings.

 

[JohnW2]

What you must consider that the current rating of flex and twin&earth cables of the same CSA, are different. I would normally expect 1.0 flex to be rated at no more than 10A V 16A for T&E and 2.5 flex at 25A v 27A for T&E. I doubt that it is an issue but worth checking your device ratings.

It really should make very little difference, and I don't understand where some of the CCC figures for flex in Table 4F3A have come from. Section 2.4 of Appendix 4 (and a note in 4D2A) seem to indicate that the figures in 4D2A can be used for flexible cable with just a correction factor of 0.95 applied to the CCC - i.e. on that basis, the CCC of 1.0mm² flex in free air (which I guess is what 4F3A relates to) should be 16.15A (17A * 0.95), not 10A as indicated in 4F3A. Anyone got any thoughts about this?

Whilst I can understand that having flexible, rather than solid/stranded, conductors may have a small effect on CCC, I understand far less how it can effect voltage drop, yet 2.4 of Appendix 4 indicates that flex has a greater voltage drop, to the tune of a factor of 1.10. That makes no sense to me, given that surface/skin effect should be negligible at 50 Hz - anyone got any ideas about the explanation? Do measurements actually confirm this difference in VD for the same CSA? (RF, are you listening?!)

Kind Regards, John