Garage Supply Cable Calcs

[amateursparky]

HI guys

If you recall on my wiring diagram my supply cable for the garage is a 6mm 3 core swa. I don't know what was going thorough my head at the time

I believe this is massive overkill for a 16A breaker. I originally designed it for 32A. Even my dad doesn't have this so again overkill. I believe the garage is about 25m away for the consumer unit. I have stepped this out and added extra since the cu is in the upper right hand corner.

As discussed previously my cable will be buried underground in a suitable cable duct.

Now thinking about it how am I going to protect it from the weight of a car since it's a drive way?

Also being in a duct would this not affect the current carrying capacity of the cable? It's going to be enclosed in the duct 99% of the way ?

Could you give me an example of a suitable duct? Am clueless about this since I've never done it before

If it's relevent it's a TN-S system. See this post

 

[ProDave]

SWA is designed to be directly burried in the ground. Just remember to lay some yellow "warning electrical cables below" tape over the top of it before filling in.

At the required 450m depth when back filled there will be no problem with vehicles driving over it.

No need for ducting.

And there's nothing wrong with 6mm SWA for a garage supply so no harm done.

 

[SPECIAL LOCATION]

Only need for ducting is if its a long run and you may need to pull a new cable in later.....

But if you think its going to be down ok for years why bother ducting?

:C

 

[batty]

I think it depends what the soil is made up of. If its full of flints a duct may be a good idea. You could of course put in some shingle to protect the SWA but as said it all depends on ground make up. Talking of ducting have you seen the price of it lately. Went to buy 100 mtr of 32mm and they wanted over £200 for it what's going on.

Wow look at this on ebay £9.95 a metre.

http://www.ebay.co.uk/itm/32MM-BLACK-ELECTRIC-CABLE-POLYDUCT-DUCTING-MAINS-SUPPLY-CABLE-CUT-LENGTH-/230752856310

 

[ProDave]

Actually the DNO up here insist their cables are run in a bed of sand to prevent puncturing of the sheath

 

[OnOff]

SWA is designed to be directly burried in the ground. Just remember to lay some yellow "warning electrical cables below" tape over the top of it before filling in.

At the required 450m depth when back filled there will be no problem with vehicles driving over it.

No need for ducting.

And there's nothing wrong with 6mm SWA for a garage supply so no harm done.

Of course at 450m deep your into the realms of mines etc which are excluded from the scope of 7671................ :coat

 

[hxsarge]

i wired a garage 2 years ago across a driveway, left the cable on top for the builder to dig in.... went back the other month and someone had clieted it over the drive... been like that 2 years apparently and im talking a huge drive with lwb vans driving up and down it 3 or 4 times a day....

 

[batty]

Actually the DNO up here insist their cables are run in a bed of sand to prevent puncturing of the sheath

Same down our way with SSE. I did a job a few years back, they wanted there cable buried in sand rather than a duct. They said it was better that way as it can loose its heat.