Advice about burying a cable under a driveway....

[RWhites]

Hi all.
I'm soon going to be having my driveway re-done and electric gates installed. To keep costs down, I'm planning to do as much of the digging-out & sub base myself as I can.

The cable for the gates will need to be run underground (about 10-12 metres in total), and I want to keep my options open for the possibility of installing lights on the gateposts etc.

Having done some searching on here, I can see that I need to use SWA.

My questions are these:
- Should I run the SWA inside some kind of ducting to make future alterations / additions / maintenance easy?
- If I do use ducting, what sort / size is 'standard' for this kind of thing?
- How deep should I bury it? (there is potential for heavy machinery in the future, as a house extension still needs to be built).
- Should I just sack the idea of ducting and use a cable with more cores than I think I need so I have some built-in future expandability?
- If I'm not using ducting, does the burying depth change?
- Is there anything else I should be considering / doing when running the cable?

Any help & opinions would be gratefully received.

Thanks in advance.
Rich.

 

[ricicle]

If you're not sure if you need ducting then you need ducting

I would run two. One for power (gate and lights) and one for any communication link that might be needed. Minimum 450mm depth and minimum 75mm diameter.
You can get it with the pull string already in.

 

[Chri5]

http://www.cablejoints.co.uk/upload/E.ON___Electricity_Cable_Ducts,_Guidance_Notes.pdf

Hope that helps

 

[plugwash]

Note that document is for electricity supplier cabling. It may be useful to read it but treat it as guidance, not as requirements.

 

[Taylortwocities]

Are you installing the electric gates & controls yourself?

If not, surely it would be best to select a supplier and have him state what will be required.

There are a lot of different systems. You may want, for instance, a pedestrian release button inside so that just one gate opens. Wiring for an intercom may mean other wiring, or some are wireless. the list, and the options are endless,

If you still don't, know. Put in just the ducts with draw cords. Cables can be pulled in later.

 

[bernardgreen]

Best to follow that guidance as otherwise accidents will happen.

A couple of days ago a on a new build site near here the fencing contractor cut through a service cable less than a spade blade deep. He needs a new spade, both he and his son suffered mild burns to their faces.

 

[ban-all-sheds]

Are you installing the electric gates & controls yourself?

Possibly unwise.

As of 29 December 2009 (its latest update), all newly installed automated gate systems are covered by the 'Machinery Directive' and should meet the stringent safety requirements laid out within. The law puts responsibility not only on the installer but also the owner of the gates ongoing (i.e. ensuring the gates are maintained accordingly to these standards).

For example, all gate systems should have safety features installed in them to prevent crushing (and this doesn't mean a set of photocells, as these may not pick up a person standing between the gates).

The gates are not allowed to exert an initial pressure of more that 400N for more than 0.75sec, dropping down to 150N for the next 5 secs, coming down to 25N after the 5 seconds has elapsed.

The majority of mains operated hydraulic ram systems will probably fail the required standard, (when fitted on their own) and will require more often than not, the fitting of safety strips which allow the gates to meet the above standards.

Gaps, shear points, crushing zones, trapping points (to name but a few) all need to be assessed and accommodated for during design & installation and suitable safety features added to ensure risks are minimised........

As with anything in life, if corners are cut or installations are compromised through the lack of competence, then accidents are going to occur, and given the number of well publicised fatalities recently you'd be mad to install gates unless you know exactly what you're doing.

(Most of the text above stolen and abridged from here: http://www.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=36562 )

 

[JohnW2]

Are you installing the electric gates & controls yourself?

It would seem probably not, if the OP actually meant exactly what he wrote:

I'm soon going to be having my driveway re-done and electric gates installed. To keep costs down, I'm planning to do as much of the digging-out & sub base myself as I can.

Kind Regards, John

 

[RWhites]

Thanks for all the input chaps.

I conclude that ducting is the way to go - a little more hassle now, but I'm never going to regret it!

I've also realised that I should be able to use the same trench for a drainage pipe I'll need to install, so I'll be able to kill two birds with one stone.

For clarity, I'm not installing the gate myself, but the gate man expects the power cable to be there ready for him. He isn't doing any ancillary electrics, just the gate power.

I'm also aware of the safety issues. When I first started to look into this a couple of years ago, I was surprised at how lax the people I was speaking to were as regards safety features - but then they never turned up to do the job.... I've got two small kids, so safety is very high on my spec list.

Cheers again.
Rich.

 

[mfarrow]

The notes Chri5 linked to are as good as the IET recommend, i.e. the ones for utilities. The only variation is that the IET, in their official guidance notes to BS 7671, recommend a minimum cover of 500mm as opposed to 450mm.

 

[fairplay]

Best to follow that guidance as otherwise accidents will happen.

A couple of days ago a on a new build site near here the fencing contractor cut through a service cable less than a spade blade deep. He needs a new spade, both he and his son suffered mild burns to their faces.

Two things spring to mind. I thought the use of swa cable was to prevent this sort of thing. Must have been a hell of a sharp spade and strong bloke to cut through swa with one blow. Also shouldn't the armour be earthed and would trip surely?

 

[EFLImpudence]

I thought the use of swa cable was to prevent this sort of thing.

It's a bit of a misnomer.

If the spade is at the same angle as the steel wire, there will be no resistance.

The steel wire is mainly to cause an earth fault, and disconnection, when the cable is penetrated.

 

[Taylortwocities]

After seven years the point of this thread is moot.

 

[bernardgreen]

I thought the use of swa cable was to prevent this sort of thing.

Service cables are not always SWA

This is an off-cut from the new service cable to my cottage laid in 2011 , it crosses under a driveway, it is in a duct.

Copper Neutral, Aluminium Live.

and no armouring.