I am going to have to have a 6mm SWA cable run to my new shed for power. I have had a quote for the job but the route for the cable is not clear. It will have to be hung from a catenary from the first floor of the house to the garage, 5.4m, at the end of the drive beside the house. I want to know if it is permissible to lay the SWA fixed on top of the corrugated asbestos/cement garage roof for about 5m before passing through the old shed and the on a second catenary, about 2.5m, before entering the new shed at eaves height. It would be virtually impossible to burry this cable. I am sure I have read somewhere that SWA cable can be slung over a distance not exceeding 3.5m without the support of a catenary but I can't find the reference, can anyone confirm or refute this? It would make life easier if I could do this.
Why not secure it along the side of the outbuildings? It would seem a better idea than just carelessly slung across a roof.
The On Site Guide is a guide to the regulations. It states. For sheathed and/or armoured cables installed in accessible positions, support by clips at spacings not exceeding the appropriate value stated in Table 4A. Table 4A states that for cable 9mm-15mm diameter, the spacings of clips for a cable run horizontally should be 350mm. for cable 15mm-20mm, the spacings of clips would be 400mm. In practice, what looks right is right (you would space your clips/cleats a little closer IMO). Slung over a roof is not acceptable.
i would say avoid messing with the asbestos roof (unless the person carrying out the work has an asbestos licence as that is dangrous stuff see a site shutdown for 3 years when asbestos was found while it was found how it was missed) so yea as been said clip to wall
To be fair, on a roof it is supported along its whole length(that which is on the roof). Surely clips are for when weight needs supporting where nothing else holds it up, like a catenary with hangers every 400mm for instance. Must say, seems a long distance if those measurements are correct! Mr. HandyAndy - Really
Slung across asbestos roof And rest of it will be a right eysore Virtually nothing is impossible! Why can't it be buried?
There is a considerable amount of concrete between the house and the shed as well as mature plants. The catenary avoids, for the first leg of the cable run, any need to dig and I'd like to keep it that way. Do any regulations anywhere prohibit the routing of SWA across a virtually flat roof? I doubt if my electrician or myself will do anything carelessly on this job.
Thank you Andy. The measurements are correct the garage is just 4.8m long but the new shed is right at the bottom of the garden. The SWA would be out of reach on an inflammable surface and shielded from view from most eyes. If there is not an actual regulation prohibiting this route I can't see the problem.
You're right. You're an educated man, and you know that. The problem is some people think inflammable means 'not flammable', in the way that 'invisible' means 'not visible'. I think that's why flammable and non-flammable are preferred. I have no idea which the OP meant when they said the roof was inflammable. Probably non-flammable, but that's the opposite of what was posted. I'm not sure it's being pedantic when the issue is whether something will easily catch fire.
It's a shame the images I tried to add to my post were not accepted. At least one of the mature plants is a Hydrangea Petiolaris, a climber that covers most of the garage with limbs up to 5cm diameter and extending above the garage roof. It was old when we moved here 35 years ago. I agree that I could grub every plant out that grows in the bed along the side of the garage wall and dig a trench for the cable. This would also mean destroying two concrete paths - still not an insurmountable problem. The big one would be the retaining wall that separates the upper and lower levels of the back garden. The new shed is in the lower part of the back garden and the wall that separates the upper and lower levels is a 23cm thick poured concrete structure about 1m tall with the top flush with the upper level garden and sunk about 30cm below the lower level garden. Clearly even this obstacle could be overcome with an awful amount of digging. I'm knocking on a bit now and try to find the easiest and simplest way to do a job nowadays. This is why I turned to this forum simply to find out if my ideas were feasible and 'legal' and with the hope that someone with experience in this field could offer a sensible solution.
The specification of the roof in my post is asbestos/cement which is of course non-flammable. Regardless of my use of the wrong word and not checking my input it should have been obvious, even to a pedant, what was meant by my description of the cable's position regarding its fire safety.
....and when the intended information is not obvious from the context......it is always advisable to use the correct technical wording. As Engineers/time served electricians we do tend to sound 'pedantic' to less skilled trades, the terminally ignorant and people in general....which is why it takes at least 10 years (and in some cases 48 years) to be good at what we do.....and answer questions from people who need help. Even syntax and punctuation can change the meaning of everything; Example: The men wrote: "A woman, without her man, is nothing." The women wrote: "A woman: without her, man is nothing." I do hope this helps to clarify my advice but if you do need 'further and better particulars' (that's a legal phrase by the way) please don't feel embarrassed to ask. A Latin phrase found on some one pounds coins reads.. NEMO ME IMPUNE LACESSIT What a scintillating and education experience it is to exchange pleasantries on this forum ! RS
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