Rank: Forum user 
|
Bit of advice please, we have had a contractor attempting to dig a trench to bury an LV 240v SWA in order to supply an electric gate he was installing for us.
Initially he was intending to bury at a depth of 50mm in concrete above the concrete reinforcement and the cover with Epoxy and back fill with concrete.
Our electrician on site informed him it needed to be 700mm iaw Edition 17.
6 weeks later the trench isn't finished and he wants another £5k to complete. He claims he is justified in charging the extra as he was perfectly OK to only bury the SWA at 50mm as Edition 17 is only guidance.
Where do we stand on this, yes in Edition 17 it is only classed as best practice but is 50mm suitably sufficient for buried services in an industrial unit carpark?
|
|
|
|
|
|
Rank: Forum user
|
May be help;
No specific requirements for depth of burial are given in the Regulations, except that the depth should be sufficient to prevent any disturbance of the ground reasonably likely to occur during normal use of the premises. Hence, a cable to outbuildings installed under a concrete path could be at 400 mm, whilst if running through a cultivated space which could be subject to double digging would be less likely to disturbance if buried at 700 mm.
Pete,
|
|
|
|
|
|
Rank: Forum user
|
|
|
|
|
|
|
Rank: Super forum user 
|
Peter has given the answer I was going to give before I left for site this morning, but didn't!
However, 50mm could be deep enough, if:
The route of the cable is known.
There is not likely to be any uncontrolled ground disturbance.
If any excavations are controlled, and can be controlled such that those working know that the cable is there.
The cable "covering" is sufficiently strong to take any travelling loads without transferring any loading to the cable. (This is the one that I think you may struggle with.)
As long as the cable covering is sufficiently strong not to break up following long term use.
Now if the original proposal is that there would be no significant vehicular traffic crossing the cable route, then potentially 50mm, may be deep enough.
That would also depend on the geometry of the trench & the filling material.
If the spark can justify his actions for burying @ 50mm and they are adequate supported with proper engineering and calculations then it could be fine.
He is designing the installation and signing for the design, therefore, he is responsible, if he is convinced it's ok, then it is his design, for which he is responsible.
If you have required the extended burial depth, then you could well be liable for the additional costs.
This really should have been sorted out before commencement, surely.
|
|
|
|
|
|
Rank: Forum user
|
Thanks for the info Paul.
Your right this should have all been picked up in the design, but this happened before I joined the company and I am picking up the loose ends on this.
The cable is going to run across the gate entrance to the car park which would have HGV's crossing so there's no way it is sufficient.
The tendering process for this job was no existent and all my company has is a basic quote with no details just a price.
I guess I can thank my predecessor for this can of worms.
|
|
|
|
|
|
Rank: Super forum user
|
Irrespective of the 17th edition [which only covers some areas] the HSE has guidance with regards to installing cables etc. in the queens highway that should be used as your guide additionally the designer should be taken to task as they are supposed to design properly
get the managers trained up in as many areas as poss especially those in procurement
|
|
|
|
|
|
Rank: Super forum user
|
bob,
The 17th edition covers everything past the DNO cutout/providers meter, for supplies that are provided at low voltage including some (a lot actually) stuff on the Queen's highway, and everything on private land, and publicly accessible land that is not the Queen's highway.
You will find that the NJUG guidance is for utility companies that are not bound by the wiring regulations.
Electrical DNO's are bound by ESQCR, which goes hand in glove with BS7671.
Whilst BS7671 is not law, neither is HSE guidance.
Depending on the current to the gates, I suspect it is VERY low in the grand scheme of things.
I am pretty sure I could have designed and installed the cable at 50mm below the surface, and it run across the entrance gate, and, ensured that it would have been safe and adequately protected.
|
|
|
|
|
|
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.