Overhead garage supply question

[Somebrightspark]

Hi,

I am currently considering the best way to go about this job for a customer who wants garage power wiring from an overhead supply cable (to replace the current 1.5mm T&E swinging in the wind supply!).

The cable will go from his under-stairs board, up through the landing to the loft, through the loft and out from above the first floor down to the garage. The distance between the house and garage is around 5 meters and over his private back garden. The height of the cable at its lowest point will be around 3 meters.

I am leaning towards running this type of cable: 4mm² 3 Core HO7RNF Rubber Flexible Cable (Cut Length Sold By The Mtr) | City Electrical Factors - https://www.cef.co.uk/catalogue/products/75559-4-0mm-3-core-ho7rnf-cable-cut-length-sold-by-the-mtr

It's heavy duty rubber (neoprene) flex which is designed to withstand UV light, oils and greases and mechanical and thermal stresses.

I'll support this cable with cable ties along a Catenery wire to take the weight of the cable and hold it securely at each end.

What do you guys think of this idea? Would this pass an NICIEC/STROMA/NAPIT assessment?

Any input appreciated,

Thanks

 

[Spoon]

Hi mate,
Just a couple of questions.
Where did you get the minimum height of 3 meters from?
Why 4mm? What breaker/rcbo size is this wired to?

 

[Midwest]

OSG Appendix D has some guidance on Overhead Wiring, height, spacing etc.

 

[kingeri]

Is it not possible to run a cable underground instead? That would be my preference.

 

[Wilko]

Hi - heightwise the OSG Table D2 has min hts of 3m if solid unjointed steel conduit used for spans 3m or less, otherwise it's 3.5m. If there is vehicle access 5.8m is listed. Same table mentions pvc, hofr and bare conductor cables. I think your one is better than pvc

Edit - sorry MW you already mentioned.

 

[Spoon]

Hi - heightwise the OSG Table D2 has min hts of 3m if solid unjointed steel conduit used for spans 3m or less, otherwise it's 3.5m. If there is vehicle access 5.8m is listed. Same table mentions pvc, hofr and bare conductor cables. I think your one is better than pvc .

That is why I was asking the OP where he got 3 meters from. He is not using steel conduit.

 

[DPG]

I don't think the op is necessarily saying it's a 3m minimum height in the regs, he seems to be just describing the length and height of what the finished job will be.
Daz.

 

[Spoon]

The height of the cable at its lowest point will be around 3 meters.

With the OP saying 'will be' I took it that he is talking about his job. If he was talking about the present install I would have expected 'is'

 

[DPG]

Yes, that's what I mean - he's saying when he's finished it then it will be 3M high, due to where the cable is coming out of the house at. I don't think he's saying that it HAS to be a minimum of 3M due to a regulation though is he?.

 

[Octopus]

3m would be tricky if its a bungalow....

 

[Midwest]

3m would be tricky if its a bungalow....

Be okay if it was a block of flats

 

[snowhead]

Would that be U.V resistant Cable ties?

 

[Dave OCD]

Would that be U.V resistant Cable ties?

Yes that's a very good point, otherwise they'll soon be falling off, white ones are the worst.

 

[westward10]

Metal cable ties and if you use flex do not pull the ties too tight and leave slack at both ends.

 

[Spoon]

Not much point in discussing what the OP is on about unless he replies.

 

[Somebrightspark]

Cheers for replies,

I'm using 4mm from a 32A breaker to a little 2 way garage board. I'll use metal/uv tie wraps

The 3M is the lowest point the cable will be as it enters through the brick of the garage.

I read somewhere that 3.5M minimum height is a recommended but not compulsory height. The entry point is above a place where literally no one would walk - skirting around the edge of the garage foundations. In practical terms the back garden drops down below that and is lower than 3.5M from the cable.

I'm using this for my STROMA assessment but I'm unsure as to how hey will weigh up installations that are safe and practical but may go into blurry territory re. the regs. I mean would they tell me to change it? There's no realistic way of having the cable come into the garage any higher and going underground would be massively disruptive and expensive for the client.

 

[Wilko]

Hi - as the OSG has recommended min hts and (if I understand correctly) you are not quite using those I think it's a coin flip on whether you get pinged for it on an Assessment. Perhaps the aerial cable route was pre existing?
Edit : I don't see Assessor instructing you to change it, but they may not accept it as the evidence they need to see from you.

 

[Midwest]

I would email Stroma and ask, no point waiting for the day of your assessment.