I have a single phase BTS supplied with a 6mm2 2C+E to inspect. This supply cable between the network supply box and switchboard, goes across a driveway (used by private vehicles, won’t be used as access to the construction site).
The builder has built a timber structure up and over the driveway the electrician has installed the cable in HD conduit and saddled it to the structure.
Regarding the height of the cable, I think it’s reasonable to take the height from table 3.8 of 3000 (4.6m; from column #1/insulated and unsheathed live conductors). Does this sound fair? It’s a bit confusing because the entirety of clause 3.12 doesn’t really include the cable type or installation method I’ve described, it’s not listed under 3.12.2, it doesn’t really fit the description of an ‘aerial conductor’. I feel there should be some mandatory minimum height for this scenario though?
Is ECP34 relevant here? Seems it would need to be installed/inspected for compliance with ECP34 if it were HV as per ESR70(2)(a). The only other reg I can find that mentions ECP34 is ESR17, which only seems to be about maintaining safe distance’s when carrying out construction, building or excavation work.
So I’m thinking ECP34 can be put to one side for this, and 3000 should be referred to?
Overhead cable in conduit
Re: Overhead cable in conduit
Stick to "3000", which clearly applies
Correct that ESR 70(2) only applies to HV; and ECP 34 applies only to "lines".
ESR 17 also applies only to "lines".
"Electric line" is defined in ESR 4.
"Lines" isn't limited to "works", and would certainly include aerial (or underground) mains from boundary to building
(which is 'installation", not "works").
So it seems ECP 34 can apply; which would give you 3.5 m [Table 1].
However everything in that Table relates to "spans", and you don't really have a span.
You refer to a 'network supply box and switchboard'; which leads me to think that you may be well removed from "lines", which would finish at that swbd.
Because the cable is supported on a structure, I would not regard it as an aerial wiring system.
And correct it certainly doesn't meet definition of "aerial conductor" [1.4.5].
Within "3000"; the whole of 3.12 relates to (unsupported) conductors suspended between supports;
and since that's not what you're dealing with, I think the clearances of table 3.8 simply do not apply.
Looking at 3.13 for cables on catenary; 3.13.3 says to treat them as if N/S aerial - which puts you back to 4.6 m
- which is 1.3 m higher than required by ECP 34!
The situation is really no different to running across the top of a garage doorway.
Just that there's only a doorway, with no garage behind it.
So I think you'll have to avoid insisting on those clearances, and just consider whether the wiring is adequately protected from external influences.
It would be reasonable to ask for a "max height" sign (each side); and maybe a bit of dayglo paint or some hi-viz flags, to attract attention.
3.12.3.2 provides a "hook" to hang this request on.
Correct that ESR 70(2) only applies to HV; and ECP 34 applies only to "lines".
ESR 17 also applies only to "lines".
"Electric line" is defined in ESR 4.
"Lines" isn't limited to "works", and would certainly include aerial (or underground) mains from boundary to building
(which is 'installation", not "works").
So it seems ECP 34 can apply; which would give you 3.5 m [Table 1].
However everything in that Table relates to "spans", and you don't really have a span.
You refer to a 'network supply box and switchboard'; which leads me to think that you may be well removed from "lines", which would finish at that swbd.
Because the cable is supported on a structure, I would not regard it as an aerial wiring system.
And correct it certainly doesn't meet definition of "aerial conductor" [1.4.5].
Within "3000"; the whole of 3.12 relates to (unsupported) conductors suspended between supports;
and since that's not what you're dealing with, I think the clearances of table 3.8 simply do not apply.
Looking at 3.13 for cables on catenary; 3.13.3 says to treat them as if N/S aerial - which puts you back to 4.6 m
- which is 1.3 m higher than required by ECP 34!
The situation is really no different to running across the top of a garage doorway.
Just that there's only a doorway, with no garage behind it.
So I think you'll have to avoid insisting on those clearances, and just consider whether the wiring is adequately protected from external influences.
It would be reasonable to ask for a "max height" sign (each side); and maybe a bit of dayglo paint or some hi-viz flags, to attract attention.
3.12.3.2 provides a "hook" to hang this request on.
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