Electrician walked out on job today

[zebragonzo]

I'm trying to get 2 external plug sockets fitted; one on the outside of the house and one at the end of the garden. I got someone in who was going to put a cable out from the house, under a path and then cleated down a wall to the plug socket at the end of the garden. This guy told me that he required a trench so I dug a trench under the path; pulling up a paving slab, gravel, sand, 3" of cement and then a few inches of soil underneath. All in all, about 12" deep, 1m wide wall to wall.

Today he came to do the work, but when he saw the depth of the trench he told me that it wasn't sufficient; rules said it needed 600mm depth. He said it was 600mm regardless of the fact I was going to relay 3" of concrete on top once the cable was in. I told my wife, in front of this guy, that we'd have to get another electrician in to fit that cable as I didn't think that 600mm was necessary if it's going under concrete. This guy got the hump, muttered something about me getting a cowboy in and then left.

Am I right that I don't need 600mm if it's laid under concrete, or do I have lots more digging to do?

 

[SPECIAL LOCATION]

Hello Zebragonzo..

From BS7671 (wiring regulations). 

and Chapter 52, "Selection & Erection of Wiring Systems"..

Regulation No 522.8.10 states the following

"buried cables, conduits & ducts, shall be of sufficient depth to avoid being damaged by reasonable foreseeable disturbance of the ground."

(NO actual depth measurement is provided.)

Now.. 

In my opinion, what is a "reasonable depth" is between you and your electrician to agree upon..

However, on the face of it, your problem of who's right or wrong...  sounds like a bit of a six-of-one and half-a-dozen-of-the-other problem..

i.e. any preparation work, (such as trench being dug), should have been agreed in writing with a clear schedule of where the trench is going & how deep it is.  etc..

Sounds to me as though you have fallen foul of the all to common "Verbal misinterpretation trap"..

Where "X" says something..  but "Y" hears something slightly different and agrees to what he/she thought "X" said..

I am open to correction from my esteemed fellow members on here..

But I always understood the 600mm depth was a 'rule of thumb'.. for running cables underground where later manual digging, (by bod with a spade), was probable.

It has never been an official 'must-do' regulation depth..

as in some other situations 600mm could be too shallow!!!  

Your first electrician has obviously got the hump and has better things to do..

I would start again, get a new person round to evaluate where you are at,

See what they are happy or not to go with..

and keep an open mind to their suggestions, but obviously question them if you think they are not in keeping with the quoted regulation..

Don't be afraid to ask them to back up their recommendations with any regulations or BS7671 guidance books/notes.

Hope that helps..

and Welcome to the forum..

the Bar is at the end of the corridor..

Guinness Guinness

SO.. beware of anything posted after midnight as it could have  Guinness influences!! 

 

[Andy™]

deep enough imo. as above, no depth stated in BS7671 (except for some special locaitons, which yours isnt)

id also say youve had a lucky escape in that the cowboy has walked off...

 

[zebragonzo]

Thanks for the replies all.

Given it's going to be under a fixed surface and the cable path will be extremely obvious (down one wall into the ground and back up out 1m away on the other wall) I don't think I need to dig deeper to prevent accidentally cutting into the cable. Further, the walls have evidence of subsidence so I really don't want to dig deeper!

I'm still angry at this guy for leaving all the parts and charging £60 for 'sourcing parts' and 'time on site.

I've tried contacting a few other people to see if anyone else is interested in the work, but I get a nasty feeling it's going to be me doing the work so I'll probably be back with more questions on that soon!

Thanks again for your help!

 

[binky]

I am open to correction from my esteemed fellow members on here..

But I always understood the 600mm depth was a 'rule of thumb'.. for running cables underground where later manual digging, (by bod with a spade), was probable.

It has never been an official 'must-do' regulation depth..

as in some other situations 600mm could be too shallow!!!  

totally agree, far too many take a recommendation and regard it as fact. You can't get more protected that 3" of concrete over the cable.

I once had someone tell me 35mm 4 core SWA needed to be cleated avery 300mm max, the response was rude! 

 

[kerching]

can't get more protected that 3" of concrete over the cable.

4"!.... sorry but it had to be said............I've had a bad day

 

[Andy™]

I've tried contacting a few other people to see if anyone else is interested in the work, but I get a nasty feeling it's going to be me doing the work so I'll probably be back with more questions on that soon!

where are you? there may be someone on here nearby

 

[zebragonzo]

where are you? there may be someone on here nearby

I'm in Gloucestershire.

Someone came around to quote today actually. Looked at the trench and said normally he'd all for 600mm deep, but considering the concrete he was happy. Restored my faith!

Fingers crossed that this will go smoothly now.

Thanks for the replies and sense of rationality everyone; yesterday was a stressful day when he walked out!

 

[Luckyboy]

Hey Zebra, 

A swa cable needs to be buried at a sufficient depth to avoid damage due to disturbance of the ground (Regulation 522.8.10). Whilst BS 7671 does not state a minimum depth, the generally recognised depth of a buried cable to prevent disturbance is 600 mm. The cable needs to be surrounded by sharp sand to avoid damage to the sheath by stones or rubble. Above the layer of sand, electrical warning tape should be used to indicate a cable is installed below. Alternatively, the cable could be installed in a pipe which would make rewiring a simpler process. If a pipe were to be used however, care must be taken to ensure that cable in the pipe would not be subject to vermin or water penetration.

Cheerio,

 

[Bruspark]

Hey Zebra, 

A swa cable needs to be buried at a sufficient depth to avoid damage due to disturbance of the ground (Regulation 522.8.10). Whilst BS 7671 does not state a minimum depth, the generally recognised depth of a buried cable to prevent disturbance is 600 mm. The cable needs to be surrounded by sharp sand to avoid damage to the sheath by stones or rubble. Above the layer of sand, electrical warning tape should be used to indicate a cable is installed below. Alternatively, the cable could be installed in a pipe which would make rewiring a simpler process. If a pipe were to be used however, care must be taken to ensure that cable in the pipe would not be subject to vermin or water penetration.

Cheerio,

Oh dear . . . 600mm is 'safe' where the ground is likely to be disturbed in normal usage (e.g. field /flowerbed)   

As the cable is to be protected with a slab and a thick layer of concrete that should defeat most attempts to carelessly dig it over the logic here should run :

How can/will this be disturbed ?  (only by lifting the paving stones (which should immediately reveal the first lot of warning tape)
How will the concrete layer be disturbed   ?   By removing  the sand  & gravel to reveal yet more warning tape on the top of the concrete and, by then, by very very careful removal with a breaking bar or hammer instead of a jack hammer

If I found that arrangement I'd be entirely happy that due care had been taken


 

 

[zebragonzo]

For anyone who comes across this one day and wants a picture to see what I'm talking about. Here's the area in question.

Seeing the finished job, does anyone still think that 600mm depth is required?

 

[binky]

For anyone who comes across this one day and wants a picture to see what I'm talking about. Here's the area in question.

Seeing the finished job, does anyone still think that 600mm depth is required?

View attachment 13394

I see no problems with that.