Flex or T&E?

[riveralt]

Doing a job next week lowering a ceiling and fitting downlighters and under cupboard lights in a kitchen. Each downlighter with have it own transformer and the transformer will be connected to the circuit with wago click flow connectors. The under cupboard lights are 230v.

All the lights will be operated from a three gang grid switch which will power the circuit.

The plan is to push the click flow connected transformer back through the downlight hole to allow easy access - so a certain degree of flexibility is needed.

I originally intended to use 1mm T&E up to the click flow connector and then flex from there through the tranformer to the light. However, I am now considering wiring the whole circuit from the grid switch using flex.

I would welcome any views on this option.

 

[ColJack]

flex is not designed for fixed installation wiring.
use T+E.. how often are you really likely to be pulling the connectors and cables back out of the ceiling?

 

[ban-all-sheds]

flex is not designed for fixed installation wiring.

But then downlighters are not designed for lighting rooms, and he's installing those....

 

[ericmark]

Over the years I have seen electricians many times say flex is not for a fixed insulation and I argued many times that caravans and the like should be wired in flex and again and again I was told no should be twin and earth.

I would love now to wave the 17th under their noses and say "I told you so" and I think to use twin and earth where it is going to make access harder and also likely to put undue strain on the cable clamps is silly.

I know it says for cookers you can use non flex (521.9.2) but I would consider if not sure then use flex. The only consideration is what flex. Not sure I would want to use 60deg flex.

 

[LoveRocket]

There is no reason whatsoever (other than price!) that flex cannot be used for fixed wiring.

 

[ericmark]

There is no reason whatsoever (other than price!) that flex cannot be used for fixed wiring.

Not quite right as flex is often rated at 60 deg rather than 70 deg so where the rating is close to limit there are problems in showing it will comply. Using high temperature flex can over come this problem I know.

However for lighting we are no where near the limits already restricted to 5/6A where ceiling roses are used so unlikely to get any where near max amps permitted for cable.

Flex does include SY cable and so at first glance you may say SY could be used instead of SWA however SY cable does not comply with BS 5467, BS 6346. BS 6724, BS 7846, BS EN 60702-1 or BS 8436 so can't be used buried at less than 50mm in wall. Not a clue why it should not comply as I am sure it is just as good as Ali-tube to BS 8436 but without the official stamp of approval it does not comply.

I know I am being pedantic and that in many cases flex can be used without any problem but "no reason whatsoever" does not really cut it with me. There are reasons but not in the case referred to in thread.

My boss once ordered a role of 185mm flex to wire concrete pumps which seemed a good idea except for problem terminating 185mm cable in a 125A plug. But then Nuclear Electric stopped us and said flex was only allowed inside the restricted access of the tower crane tracks and was not permitted anywhere else on their building sites at over reduced low voltage.

Which if you know the price of 185mm flex was not very good news. It was hidden and we hoped no one would realise the error. Next job he was an electrician again so may be some one did find out?

 

[ban-all-sheds]

Flex does include SY cable and so at first glance you may say SY could be used instead of SWA however SY cable does not comply with BS 5467, BS 6346. BS 6724, BS 7846, BS EN 60702-1 or BS 8436 so can't be used buried at less than 50mm in wall. Not a clue why it should not comply as I am sure it is just as good as Ali-tube to BS 8436 but without the official stamp of approval it does not comply.

Put that in a comment to the IET re the 17th Amendment - might get it changed.

 

[LoveRocket]

Flex does include SY cable and so at first glance you may say SY could be used instead of SWA however SY cable does not comply with BS 5467, BS 6346. BS 6724, BS 7846, BS EN 60702-1 or BS 8436 so can't be used buried at less than 50mm in wall. Not a clue why it should not comply as I am sure it is just as good as Ali-tube to BS 8436 but without the official stamp of approval it does not comply.

Put that in a comment to the IET re the 17th Amendment - might get it changed.

Outstanding suggestion!

There doesn't seem to be any consistency with regards to which cables are deemed suitable for concealed (<50mm) runs without RCD protection.
There are various approaches which ensure that a nail etc would be in contact with earth before it hits a phase conductor, such as SY cable, earthed capping, split-con etc, but the regs don't permit them.

Go for it Eric!

 

[ban-all-sheds]

Why was split-con removed from the list?

 

[LoveRocket]

Why was split-con removed from the list?

No idea. Obviously it's no good for switch drops, but it's a damn sight easier to work with and more practical than SWA. It's still good enough for DNOs to bury under main roads, but not good enough for us to use under a bit of plaster.

 

[skenk]

I've always wondered what's so special about 50mm anyway. round here it's not uncommon to find 25-30mm of old crumbly plaster so to get a decent fixing you have to drill in more than 50mm anyway

 

[ColJack]

split con is only eathed half way round isn't it? the other half of the "armour" is the neutral strands?

and as is spirals round it, there's no way to garuntee that it will have the earth side towards the idiot with the pitcure hook in his hand..

SY sheath is a criss cross pattern with sizeable gaps in the weave on some of the makes, so again, there's the chance that the guy with the picture hook could miss the earthed metalic sheath while nailing in..

SWA, each strand generally touches so it's almost impossible to get a nail in without hitting earthed metal first, and ali-tube the metalic sheath is solid all the way round..

as for flex in a caravan, that's hardly a fixed installation is it? it's a giant portable appliance....

 

[holmslaw]

..

 

[ColJack]

it's more likely for idiots with picture hooks and nails..
they don't tend to be over 2 inches long.. it's only a picture fgs.. and you can't really nail into a brick, just the plaster..

 

[ban-all-sheds]

They make up for the times I drill a 37mm one, and end up having to trim the plug flush with the wall with a Stanley knife