Digging a trench. Line it?
Discussion
105.4 said:
I’ve ordered 10m of this stuff to sleeve the cable with.
Why line the trench with pea gravel though? To help with drainage? How necessary would this be, (on a scale of 1-10)?
Would a couple of inch below the cable and a couple of inch above be sufficient?
You don't need to sleeve that mains cable & the reason for putting it in a duct is so that you can pull other cables through if necessary - eg a network cable to connect the charger to a current transformer. What diameter is the green conduit? Unless it's at least 50mm you'd be better off laying it in separate for any future cables - or use one for the mains & run another spare if your 10m coil is long enough. Why line the trench with pea gravel though? To help with drainage? How necessary would this be, (on a scale of 1-10)?
Would a couple of inch below the cable and a couple of inch above be sufficient?
Mr Pointy said:
You don't need to sleeve that mains cable & the reason for putting it in a duct is so that you can pull other cables through if necessary - eg a network cable to connect the charger to a current transformer. What diameter is the green conduit? Unless it's at least 50mm you'd be better off laying it in separate for any future cables - or use one for the mains & run another spare if your 10m coil is long enough.
The green conduit is 52mm.Fracking is an on / off thing around here. The imminent change of Government may see fracking back on the table, (along with the localised Earth tremors associated with it). If the cable is in conduit, it reduces the chances of the cable becoming damaged via circumstances beyond our control.
Added to which, if the driveway is ever dug up, the cable encased in conduit is another layer of protection.
Is the above overkill? Perhaps. But at under £40 and an extra 15 minutes work, I’d consider it to be a value for money insurance, although I could understand why some may disagree.
With any job, I’d rather do it once and do it right, than run into problems ten years down the line and wishing I’d done things differently. Especially when that ‘differently’ costs so little time and money.
JuanCarlosFandango said:
Isn't there a risk the conduit will fill with water/silt? Or does it not matter?
Potentially, yes. Although I would consider that risk to slight, and even if it does, for any negative effects of it doing so to be even smaller.It’s almost a Catch 22 situation, but one in which I consider it to be better for the cable to be ran through a flexible conduit.
No its not overkill, if you ever need to replace / uprate that cable, or add something to it (e.g. more twisted pairs cables for ethernet or remote CT clamps) then instead of thinking "oh bugger, I didn't think of that" you can just pull it through.
See this excavation on my driveway when I had a new 3-phase service cable installed into my garage - this is the depth the DNO installed their street cable to which is 600mm IIRC. The supply cable went in at about 450mm. My own private electrical ducts around the other side of the plot were installed approx. 400-450mm deep and I took that as standard for low voltage electrical cabling. But that's a whole house supply not just a single EV charger.
Whilst this hole was open courtesy of the DNO and their contractors, I took the chance to throw another 50mm flexible conduit from the garage area to the far side of the driveway 'just in-case' I ever feel like installing a 3rd EV charger 'somewhere over there'. I probably won't, but it's handy to know I could. Or maybe even just to install some Hue lights and a POE security camera on the far side of the garden.
In every run I installed SWA inside conduit as it just seemed like the logical thing to do in-case rodents ever got at it.
See this excavation on my driveway when I had a new 3-phase service cable installed into my garage - this is the depth the DNO installed their street cable to which is 600mm IIRC. The supply cable went in at about 450mm. My own private electrical ducts around the other side of the plot were installed approx. 400-450mm deep and I took that as standard for low voltage electrical cabling. But that's a whole house supply not just a single EV charger.
Whilst this hole was open courtesy of the DNO and their contractors, I took the chance to throw another 50mm flexible conduit from the garage area to the far side of the driveway 'just in-case' I ever feel like installing a 3rd EV charger 'somewhere over there'. I probably won't, but it's handy to know I could. Or maybe even just to install some Hue lights and a POE security camera on the far side of the garden.
In every run I installed SWA inside conduit as it just seemed like the logical thing to do in-case rodents ever got at it.
Edited by theboss on Monday 6th May 20:06
105.4 said:
JuanCarlosFandango said:
Isn't there a risk the conduit will fill with water/silt? Or does it not matter?
Potentially, yes. Although I would consider that risk to slight, and even if it does, for any negative effects of it doing so to be even smaller.It’s almost a Catch 22 situation, but one in which I consider it to be better for the cable to be ran through a flexible conduit.
NB I suspect the real "risk" here is that the electrician demands different cable to what you are installing (they always seem to want mega cables), not that the land might move. Maybe I'm under-estimating fracking and you're in the middle of Balcombe, who knows.
And if the land does move, the armoured SWA will last a lot longer than conduit. It's very tough cable. I'd keep the SWA out of the conduit. It's also more work getting it through.
The last two replies from ‘theboss’ and ‘biggiless’ highlight the issues perfectly.
What I know about the building game could be written on the back of a postage stamp, so I’ll make the assumption that both of you know what you are talking about.
But yet both of you have differing opinions on what would be the best option.
I’m not suggesting that either of you are wrong. In fact both of you are probably right. It’s just that it’s a 50-50 coin toss as to which option is best.
I’m told that it is armoured, (SWA) cable that is going to be used. Even so, I am going to stick with running it through conduit with gravel above and below to help aid drainage.
In some ways I’ll be making a good decision. In other ways I’ll be making a poor decision.
What I know about the building game could be written on the back of a postage stamp, so I’ll make the assumption that both of you know what you are talking about.
But yet both of you have differing opinions on what would be the best option.
I’m not suggesting that either of you are wrong. In fact both of you are probably right. It’s just that it’s a 50-50 coin toss as to which option is best.
I’m told that it is armoured, (SWA) cable that is going to be used. Even so, I am going to stick with running it through conduit with gravel above and below to help aid drainage.
In some ways I’ll be making a good decision. In other ways I’ll be making a poor decision.
105.4 said:
The last two replies from ‘theboss’ and ‘biggiless’ highlight the issues perfectly.
What I know about the building game could be written on the back of a postage stamp, so I’ll make the assumption that both of you know what you are talking about.
But yet both of you have differing opinions on what would be the best option.
I’m not suggesting that either of you are wrong. In fact both of you are probably right. It’s just that it’s a 50-50 coin toss as to which option is best.
I’m told that it is armoured, (SWA) cable that is going to be used. Even so, I am going to stick with running it through conduit with gravel above and below to help aid drainage.
In some ways I’ll be making a good decision. In other ways I’ll be making a poor decision.
Total novice here but learned a few things whilst 'project managing' and luckily ran into some very good electricians who seemed to know exactly what they were doing and did a very neat job of the install, so I went with whatever they recommended. I believe the SWA was necessary for the 5-15m at either end that wasn't contained in the duct, and in any case the guys weren't 'phased' about hauling 50m of 16mm 5-core through a gently curved duct, although it helped that I installed 110mm for that route i.e. it was a narrow cable getting chucked down a capacious void (no puns please).What I know about the building game could be written on the back of a postage stamp, so I’ll make the assumption that both of you know what you are talking about.
But yet both of you have differing opinions on what would be the best option.
I’m not suggesting that either of you are wrong. In fact both of you are probably right. It’s just that it’s a 50-50 coin toss as to which option is best.
I’m told that it is armoured, (SWA) cable that is going to be used. Even so, I am going to stick with running it through conduit with gravel above and below to help aid drainage.
In some ways I’ll be making a good decision. In other ways I’ll be making a poor decision.
The end result is 2x22kW zappi on opposing sides of the garage with all the cables fished away neatly, hard-wired ethernet and CT where necessary. The house is back-fed from the new distribution board, currently on one phase but we provided a 5-core SWA back to the house so eventually I can replace its consumer unit with another 3ph distribution board and balance everything out.
It's a good new electrical infrastructure that future-proofs the house nicely.
A quick update
The trench was finally dug to a depth of 400mm…..right up until a couple of feet away from the wall of the house where I encountered the foundations of the property 200mm below the ground.
A quick chat with the electricians and their suggestion, (in writing), was to dig out the foundations of my property so that the cable could be routed at the required depth right up to the wall
Now I’m no structural engineer, but this seemed like a foolish idea to me.
As the requirement is the bury the cable 400mm below the surface of the ground, and the ground cannot be dug any deeper, a simple solution was the raise the level of the ground a couple of feet away from the house wall by placing bricks on the driveway and covering them with dirt. Anyone who was so inclined in such a situation could easily just kick the bricks / dirt out of the way once the electrician has come back tomorrow to install the charger
The armoured cable was run through the 52mm conduit. Below the conduit is 50mm of small, smooth pebbles, with another 50mm placed on top. Above that is well packed-down earth, with a long line of bricks just below the surface to make it obvious that there’s a trench / live cable underneath.
I’ve temporarily capped the ends of the conduit off with plastic bags to stop the conduit filling with water. Once the electrician has finished installing the charger, I’ll cap those off properly with expanding foam.
The final problem is how to get rid of around 750-800kg of rubble. I did phone a couple of local skip companies, and the best price I’ve got is £130+VAT for a 24 hour rental of a 2 yard skip, which is extortionate IMO, and the local tip will only take 50kg.
I’m imagining something along the lines of The Great Escape with what the PoW’s did with all of the dirt from Tom, Dick & Harry
The trench was finally dug to a depth of 400mm…..right up until a couple of feet away from the wall of the house where I encountered the foundations of the property 200mm below the ground.
A quick chat with the electricians and their suggestion, (in writing), was to dig out the foundations of my property so that the cable could be routed at the required depth right up to the wall
Now I’m no structural engineer, but this seemed like a foolish idea to me.
As the requirement is the bury the cable 400mm below the surface of the ground, and the ground cannot be dug any deeper, a simple solution was the raise the level of the ground a couple of feet away from the house wall by placing bricks on the driveway and covering them with dirt. Anyone who was so inclined in such a situation could easily just kick the bricks / dirt out of the way once the electrician has come back tomorrow to install the charger
The armoured cable was run through the 52mm conduit. Below the conduit is 50mm of small, smooth pebbles, with another 50mm placed on top. Above that is well packed-down earth, with a long line of bricks just below the surface to make it obvious that there’s a trench / live cable underneath.
I’ve temporarily capped the ends of the conduit off with plastic bags to stop the conduit filling with water. Once the electrician has finished installing the charger, I’ll cap those off properly with expanding foam.
The final problem is how to get rid of around 750-800kg of rubble. I did phone a couple of local skip companies, and the best price I’ve got is £130+VAT for a 24 hour rental of a 2 yard skip, which is extortionate IMO, and the local tip will only take 50kg.
I’m imagining something along the lines of The Great Escape with what the PoW’s did with all of the dirt from Tom, Dick & Harry
I just buried a 10mm armoured cable for an office/garage feed across the garden/drive (in all 70m) and the electrician was happy at 450mm, with sand below and tape on top. Just ask the electrician what he is happy with. The fact yours is under a solid drive, I would expect him to be happy with what you have done.
Good job - well done!
I think you would have been fine going through the foundations (to a garage?) in an isolated spot. There might have been a bit of settlement requiring making good I guess so your method is less grief that way.
To avoid 16 trips to the tip I'd pay for a skip but absolutely appreciate everyone has a different threshold
I think you would have been fine going through the foundations (to a garage?) in an isolated spot. There might have been a bit of settlement requiring making good I guess so your method is less grief that way.
To avoid 16 trips to the tip I'd pay for a skip but absolutely appreciate everyone has a different threshold
Job done, well, except for getting rid of the rubble. I’m going to be tight and take it to the several local tips over a couple of week period.
The charger is an EVEC somethingorother
All I know is that it can charge two EVs at a time.
Trench? What trench?
Oh dear ! The bricks covered with dirt that were creating a raised hump in the driveway so that the cable was 400mm under the surface of the ground seem to have been stolen. I’ve no idea how that might have happened.
I’m sorry, but there was no way that I was going to dig out the foundations of the house just to lay a cable. That seems ridiculous to me.
At least now I can get the scrap Citroen shifted, which will no doubt temporarily please ‘er indoors’.
The charger is an EVEC somethingorother
All I know is that it can charge two EVs at a time.
Trench? What trench?
Oh dear ! The bricks covered with dirt that were creating a raised hump in the driveway so that the cable was 400mm under the surface of the ground seem to have been stolen. I’ve no idea how that might have happened.
I’m sorry, but there was no way that I was going to dig out the foundations of the house just to lay a cable. That seems ridiculous to me.
At least now I can get the scrap Citroen shifted, which will no doubt temporarily please ‘er indoors’.
Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff