Flex cable outside?

[D Skelton]

Am I looking in the wrong place? Coz I can't seem to find anywhere in the regs that suggest you can't use flex outside in areas where they won't be exposed to mechanical damage. An example would be spurring off an upstairs ring and taking the flex from its fcu, through the wall, outside, and along the outside wall to a security light?

I did a job the other day where we used NYY cable for a load of outside sign lighting above a shop. Could we have used flex in this situation?

 

[WDMDL]

521.9.3 refers, but only to imply that it must be fit for purpose, eg not all flexes are suitable for the temperature range, exposure to UV from the sun, etc.

So maybe an H07RN-F type to BS7919 would have been suitable?

Simon.

 

[Pinto Baz]

521.9.3 refers, but only to imply that it must be fit for purpose, eg not all flexes are suitable for the temperature range, exposure to UV from the sun, etc.

So maybe an H07RN-F type to BS7919 would have been suitable?

Simon.

I would agree with that. And I'll take this oppertunity to ask: I have alway been told that it is not acceptable to use flex within the installation, it must always be wired in twin and earth, but can anyone tell me why?

 

[D Skelton]

I see, so it's the UV protection and temperature that's important. Is NYY cable most peoples choice then for outside cable that won't be exposed to mechanical damage?

It's just that the cable coming from the actual display lights to our outside, wall mounted JB's was just normal white flex. It confused me to think that if this cable wasn't fit for purpose, which I've always been lead to believe, then why would the manufacturer sell outside lights that use normal flex? And doesn't that just defeat the objective as we'd already wired up the JB's with NYY

 

[eskimo39]

I have wired outside lights with Arctic Flex which has massive positive and negative temperature protection. I don't like terminating flex so have started using bootlace ferrules and have had no problems. I have seen old installations wired in flex with no problems also, but at the same time see old T&E which is cracked etc.

 

[D Skelton]

Only problem with Arctic is that im sure the customer wouldn't have wanted bright yellow cables on the front of their shop. I still don't understand why if the lights are fitted with rougly a meter of normal flex, then why can't the rest of the outside part of the circuit be in normal flex too? Not having a go, just very confused

 

[WDMDL]

There's also the suitability of the terminations to consider - you're not supposed to use fine stranded conductors in plain screw terminals as they can be cut through - you need to think suitable crimps or bootlace ferrules etc or use the type of screw terminal where the the screw does not act directly on the conductor.

Was it "normal" white flex though? It's worth checking the spec printed/moulded on the cable sheath, to see what it is suitable for.

Oh, and the installation will be easier and neater with a rigid cable like NYY rather than flex - think of all the sag between clips (or the amount of clips to keep it neat?)

Simon.

 

[D Skelton]

You are totally right about the tidyness of the installation with the use off NYY, it's just a ******* to strip! Regarding correct termination, NYY is single core so had no choice but to terminate it in the JB's along with the flex at the same time. I just made sure in each termination, that the flex was protected from the screw by the single core.

Finally, yes, I'm positive it was just normal white flex attached to the lights. Was really flimsy looking stuff, I was quite suprised actually.

Edit: Where I say it's a ******* to strip, well, it is up the top of a very wobbly ladder haha

 

[Paul.M]

I would agree with that. And I'll take this oppertunity to ask: I have alway been told that it is not acceptable to use flex within the installation, it must always be wired in twin and earth, but can anyone tell me why?

Have a look in the brb and compare tables 4D5 flat t&e against table 4F2 or any other comparison through the flex versus solid and you can see the difference. Also termination as above in screw terms not good. Flat t&e is flat for a reason, easier to clip and plaster over etc and also better with the cpc in the middle than spiral. Must be loads more but its getting late, others will inform I'm sure. Good point though.

 

[Deleted member 26818]

There's no actual Regulation preventing you from using flex inside or out on any part of an installation.
The same rules apply to flex as to any other type of cable, fit for purpose etc.
Precautions have to be taken to prevent separation or spreading of individual wires when making fine wire terminations.
This can be through the use of special screw terminations, bootlace ferrules, tinning or simply twisting and doubling over.

 

[D Skelton]

Thank you all

 

[ian]

I am going to be in the minority here, but personally I can’t see anything wrong with using flex outside should someone want to. It does not say any where in the regs that you cant. Like every cable precautions have made against mechanical damage etc. that being said I use NYY. but reserve the right to use flex should I wish to.

Ian

 

[Deleted member 9648]

I'm with Ian.....as long as not liable to mechanical damage and suitable for the environment there is no reason why flex should not be used in the situation described in the OP.

 

[SKY]

Now I know the below is not the correct way.

My father in law has had a bit of white 2.5mm flex running from the house to his shed (approx 3m), this cable is cleated to a wooden frame and then suspends itself across a 1m span into the shed.
I think he said that he took it off an old extension lead.
The cable is out of reach as it come out of a bedroom so it about 3m up in the air.

My father in law swears that this cable has been there for approx 20 years in all weathers, it was meant as a temp fixture when they moved in but it worked ok so he just forgot about it.
When I was last cleaning the windows for him I took a look at the cable and flex was in good condition, it was very slightly crazing where the plastic was drying out but looking at it I feel its good for another 5 years at least.

The cable runs a ceiling battern and one double 13a socket.

As he said he got the cable from an old extension lead so the cable must have the age of approx 25 years.

I said to him I wanted to do a test on the cable but he said if I touch it it would prob stop working.