Installing underground SWA for Electric Car charging station

[RFw3Duwrd7Yu]

I'm pulling out some unruly hedges and putting in a gravel driveway in front of the house, and this is the intended location for a new EV (probably a Renault Zoe). I know the charging station will require installation by a proper electrician (probably one of these: http://pod-point.com), but am hoping to save some time and money by putting in the wire myself. Our consumer unit is in the middle of the house, about 6m to the front, and then the front garden is another 7m or so long. Given the fact that wire is (relatively) cheap, I'm thinking I'll put in 32a 6mm SWA for the run. Question is: should I put this in some kind of pva conduit to hold the wire? And how deep should I bury it? This is my first go at installing outdoor electrics, so want to be sure I do things properly.

 

[oldbutnotdead]

You need to get whoever is installing the cjarge point to spec the cable. Much better plan is just bury a 50mm duct (do 2 if its going to the boundary, it'll make a new supply cable or FTTP install loads easier.
Bury it min 600mm, pref deeper. Take lots of pics, bed ducts in sand, warning tape, sand, hard fill (brivks or concrete) then tape then soil. Obey bend radius for biggest cable that'll fit down it.

 

[RFw3Duwrd7Yu]

Great - 50mm was what I was thinking. And I was also planning to double-up, for ethernet, fiber etc. Really grateful for tips re: depth, sand & hard fill. Should I try to route with the perimeter of the garden rather than a straight run so that I can more easily mark location?

 

[Aragorn84]

I would just put the cable in, personally. Everyone on here loves banging on about getting the spark to specify things like this, but has anyone actually met a spark, who when shown two ends of an pre-installed SWA cable, has refused to use it because he didnt see how it was buried? 6mm is fine. How do you intend to terminate the end of the cable?

I did the same thing when i got my EV charger in the old place. I had the ceilings down in the bathroom some months before, so ran some 10mm (H07RN-F in my case, didnt want to be manhandling SWA thru the house) from the Consumer unit, up thru the roof space and out to a Wiska box on the external wall. I also supplied a matching enclosure to my main CU, with an isolator and 40A fuse holder.

The guys were absolutely delighted that they didnt have to try to get the cable out thru the house, and just had a short run of external SWA from the Wiska box to the charger, and had zero complaints about using the supplied equipment.

 

[oldbutnotdead]

Go straight line unless it would get inhe way of any other building plans you may have. Marking is then small plate on front wall of house, another one inside garden boundary wall. Bends & SWA best avoided if possible (no choice about down & up)

 

[bernardgreen]

Take lots of pics, bed

Include a ruler or yard stick to make it clear how deep the trench and cable/duct are.

 

[SUNRAY]

I would just put the cable in, personally. Everyone on here loves banging on about getting the spark to specify things like this, but has anyone actually met a spark, who when shown two ends of an pre-installed SWA cable, has refused to use it because he didnt see how it was buried? 6mm is fine. How do you intend to terminate the end of the cable?

Yes there are sparks who refuse to use a new buried cable, or refuse to accept responsibility for it if they do use it. two reasons; 1, they can't sign to say they designed or installed it & 2, they have missed out on the money to install it.

You need to get whoever is installing the cjarge point to spec the cable. Much better plan is just bury a 50mm duct (do 2 if its going to the boundary, it'll make a new supply cable or FTTP install loads easier.
Bury it min 600mm, pref deeper. Take lots of pics, bed ducts in sand, warning tape, sand, hard fill (brivks or concrete) then tape then soil. Obey bend radius for biggest cable that'll fit down it.

Include a ruler or yard stick to make it clear how deep the trench and cable/duct are.

Both excellent advice, make sure the depth is uber obvious by making sure the measure is readable in the pics or leave a shovel standing in the trench on top of the duct etc.

I did the same thing when i got my EV charger in the old place. I had the ceilings down in the bathroom some months before, so ran some 10mm (H07RN-F in my case, didnt want to be manhandling SWA thru the house) from the Consumer unit, up thru the roof space and out to a Wiska box on the external wall.

I can think of a number of professionals who would have walked away from a lump of HO7, especially on the external wall.

 

[Aragorn84]

I can think of a number of professionals who would have walked away from a lump of HO7, especially on the external wall.

Why, what exactly is wrong with H07?

 

[Aragorn84]

two reasons; 1, they can't sign to say they designed or installed it & 2, they have missed out on the money to install it.

If its the latter, they're <insertswearword> and can GTFO. If its the former, then well thats upto them, but given appropriate measures are taken, such as those mentioned with photos and whatnot, then i think they're being a bit unreasonable. Ofcourse, there are plenty other sparks out there who are not unreasonable, so they can have the work instead.

 

[SUNRAY]

If its the latter, they're <insertswearword> and can GTFO. If its the former, then well thats upto them, but given appropriate measures are taken, such as those mentioned with photos and whatnot, then i think they're being a bit unreasonable. Ofcourse, there are plenty other sparks out there who are not unreasonable, so they can have the work instead.

But they can't legally sign to say they designed and installed...

Having seen some of the botched work done by some, I can't say I blame them.

Why, what exactly is wrong with H07?

There is nothing at all wrong with HO7 when used in a sensible manner.

 

[Aragorn84]

But they can't legally sign to say they designed and installed...

Having seen some of the botched work done by some, I can't say I blame them.

Sure, but you cant really botch up burying an cable, and some quick photos etc should be enough to show its installed sensibly. If he feels really strongly, note on the paperwork that the cable was pre-existing.

Sparks must do a huge proportion of work where they cannot possibly ensure cables are installed sensibly. If you fit a new CU, your not digging every cable out the wall to ensure its routed properly...

There is nothing at all wrong with HO7 when used in a sensible manner.

Exactly, so what do you think is not sensible about my H07 use, that would cause a spark to walk away?

 

[JohnW2]

But they can't legally sign to say they designed and installed...

As has been said, in many cases (like the one we're discussing) that's just a theoretical technicality. As said, if all we're talking about is a buried cable, and if extensive photos are available (as suggested) which show exactly how/where it has been buried, then I think it's perfectly reasonable for an electrician to treat it as if he/she had 'designed and installed' it himself/herself.

... and, as also been said, if the electrician concerned is not that reasonable, then I am sure that there are plenty of reasonable ones out there who I am sure would be happy to take ones money.

Albeit in totally different contexts, I not uncommonly put my name to work 'as if I had done it myself' even though it is at least partially someone else's work - provided that I have adequate evidence (analogous with the photos in this discussion) that it has been done in the way that I would have done myself.

Kind Regards, John

 

[SUNRAY]

Exactly, so what do you think is not sensible about my H07 use, that would cause a spark to walk away?

I haven't seen your installation including how it's installed, however HO7 is not normally used as fixed wiring especially in domestic settings and I for one would certainly look very closely before contemplating it's use.

you cant really botch up burying an cable

Oh yes you can

, and some quick photos etc should be enough to show its installed sensibly. If he feels really strongly, note on the paperwork that the cable was pre-existing.

Indeed but there is a reasonable assumption that existing wiring is installed in a reasonable manner, However there is a big difference between an existing circuit and comething installed by the customer [without consultation with the electrician], usually with the express purpose of saving money. Yes I fully understand and accept the concept of building/landscaping works and when appropriate photos are available the situation can be sensibly assessed.

So talking of quick pictures...

Finding something like this which was declared as buried 900mm down does tend to make many professionals wary/sceptical.
To add perspective to the picture it's a brown [sewer style] pipe less than 150mm down, provided for 2 armoured cables. For some unknown reason theres a hole in it and this is where the rats had originally created a way in or out. A slab had been placed over it [shown by lack of vegetation] to stop them and all they did was keep digging.

Or this one, not very clear but there's a split con and a white alarm cable running right through, a couple of SWA's heading from the bottom of the picture into the duct in each direction and of course the elephant in the room a water pipe too. Again this is buried only a few inches down and I found it covered with a big and very rotten blue 'tarpaulin' shoved over the gap and topped of with a pallet:

This duct is known to be buried much deeper, in fact a trench for a sewer was dug across its path, not more than 20m away, to a depth of some 1.8 to 2m deep without finding it and the access pit another 20m further on finds the ducts at over 1m down.

And you wonder why electricians are wary of others installing for them without consultation?

 

[SUNRAY]

As has been said, in many cases (like the one we're discussing) that's just a theoretical technicality. As said, if all we're talking about is a buried cable, and if extensive photos are available (as suggested) which show exactly how/where it has been buried, then I think it's perfectly reasonable for an electrician to treat it as if he/she had 'designed and installed' it himself/herself.

... and, as also been said, if the electrician concerned is not that reasonable, then I am sure that there are plenty of reasonable ones out there who I am sure would be happy to take ones money.

Albeit in totally different contexts, I not uncommonly put my name to work 'as if I had done it myself' even though it is at least partially someone else's work - provided that I have adequate evidence (analogous with the photos in this discussion) that it has been done in the way that I would have done myself.

Kind Regards, John

I don't disagree with any of this John. I'm only explaining it's not always plain sailing.

A simplistic comparison; a building inspector would expect to see the trench for foundations before filling with concrete, N'est-ce Pas?

 

[Aragorn84]

Ofcourse, theres always cowboys. But hes asking on here for advice, and if hes given best practice for burial and does that, then whats the issue?

However there is a big difference between an existing circuit and comething installed by the customer [without consultation with the electrician], usually with the express purpose of saving money.

Is there though? How do you know any of those existing circuits were installed correctly, and werent lashed up by some clown? I'm no electrician, but having lived in a few houses, theres always been some "horrors" with the wiring that i've had to rectify.

Infact your pics show exactly that, none of those installations are new, and if you hadnt been looking for rats, you'd never have found the shallow buried cable, and if you'd been invited in to do a board swap or whatever on one of those installs its unlikely you'd have actually inspected the cable routing.