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Discussion Starter · #1 ·
Hi everyone,

First-time poster...

Firstly, thank you for all the super information on this forum. It has been great to read, and I'm hoping the experts on here can provide a bit of help. I'm no expert, so apologies in advance if I miss off any crucial information!

I'm getting ready to install an EV charger (I'm looking at the Andersen A2) at home, in advance of getting an EV. There's an easy solution to mount it to the wall of my house (I've had quotes for standard works from a few installers) but my preferred option is to install it on my garage, which is detached.

My current setup is as follows... there is a 40A fuse on my main consumer unit for the garage, and I have an armoured 2.5mm2 cable taking power to the garage. The cable length is only about 3 or 4 metres - the garage is just the other side of a side passageway. The cable is mounted to the side of the house, then goes in a shallow trench under some gravel, and then into the garage. It feeds a small consumer unit in the garage (I know I need to replace that because there are no spare slots) which powers a couple of plug sockets and a single light.

So, my questions are:
  • From everything I have read, my existing 2.5mm2 cable that feeds the garage is not sufficient - am I right?
  • Would simply installing a thicker cable solve the problem?
  • If so, what thickness cable do I need to go for?
  • Would installing a thicker cable require me to bury it? (this isn't really an option because I would need to dig up a path!)
Many thanks in advance, guys!

Adam
 

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Hi everyone,

First-time poster...

Firstly, thank you for all the super information on this forum. It has been great to read, and I'm hoping the experts on here can provide a bit of help. I'm no expert, so apologies in advance if I miss off any crucial information!

I'm getting ready to install an EV charger (I'm looking at the Andersen A2) at home, in advance of getting an EV. There's an easy solution to mount it to the wall of my house (I've had quotes for standard works from a few installers) but my preferred option is to install it on my garage, which is detached.

My current setup is as follows... there is a 40A fuse on my main consumer unit for the garage, and I have an armoured 2.5mm2 cable taking power to the garage. The cable length is only about 3 or 4 metres - the garage is just the other side of a side passageway. The cable is mounted to the side of the house, then goes in a shallow trench under some gravel, and then into the garage. It feeds a small consumer unit in the garage (I know I need to replace that because there are no spare slots) which powers a couple of plug sockets and a single light.

So, my questions are:
  • From everything I have read, my existing 2.5mm2 cable that feeds the garage is not sufficient - am I right?
  • Would simply installing a thicker cable solve the problem?
  • If so, what thickness cable do I need to go for?
  • Would installing a thicker cable require me to bury it? (this isn't really an option because I would need to dig up a path!)
Many thanks in advance, guys!

Adam
Pretty much you are right.
You need a bigger cable.

Re how the cable is run, generally best to do the job correctly even if this means a few broken eggs for your omelette.
 

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Hi everyone,

First-time poster...

Firstly, thank you for all the super information on this forum. It has been great to read, and I'm hoping the experts on here can provide a bit of help. I'm no expert, so apologies in advance if I miss off any crucial information!

I'm getting ready to install an EV charger (I'm looking at the Andersen A2) at home, in advance of getting an EV. There's an easy solution to mount it to the wall of my house (I've had quotes for standard works from a few installers) but my preferred option is to install it on my garage, which is detached.

My current setup is as follows... there is a 40A fuse on my main consumer unit for the garage, and I have an armoured 2.5mm2 cable taking power to the garage. The cable length is only about 3 or 4 metres - the garage is just the other side of a side passageway. The cable is mounted to the side of the house, then goes in a shallow trench under some gravel, and then into the garage. It feeds a small consumer unit in the garage (I know I need to replace that because there are no spare slots) which powers a couple of plug sockets and a single light.

So, my questions are:
  • From everything I have read, my existing 2.5mm2 cable that feeds the garage is not sufficient - am I right?
  • Would simply installing a thicker cable solve the problem?
  • If so, what thickness cable do I need to go for?
  • Would installing a thicker cable require me to bury it? (this isn't really an option because I would need to dig up a path!)
Many thanks in advance, guys!

Adam
What you didn't mention was whether or not you could bypass your existing main consumer unit and cable directly from the supply downstream of your meter to the garage.
 

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Kia e-Niro 4 MY20, Zoe Z.E.50 GT Line
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If you want to draw 32A you’ll need a new cable. It doesn’t need to be buried. It can be clipped to a wall. Sounds like the current cable is installed that way. I, personally, think it’s a good idea to take a separate feed from a dedicated consumer unit at the meter, rather than running through the house CU but that’s just me. You could likely use the existing setup in the meantime if you restrict to 16A. Most charge units can do this, software or dip switch selectable (don’t know about the Andersen) and some cars can limit max current. Don’t rely on the latter
 

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As above, if you can take a supply from the tails ahead of the house CU then that's the better way to go. 6mm² SWA should be fine over that distance.

Ideally the cable should be buried 600mm down, but there are other options, as there are no hard and fast regs covering what's adequate, it's all down to the assessment of the person doing the installation. You can use additional mechanical protection over a cable that's buried at a shallow depth, for example. What's needed is protection that's good enough to make it obvious to someone weilding a spade that there is something there, before the spade goes through the cable. I've used left over precast concrete wall capping to protect a shallow cable run in the past, or you could buy the proper protection plates (not my favourite choice). As it's a short run, I'd be inclined to just put the cable inside a length of 25mm galvanised steel conduit for protection.

If digging up the path isn't an option at all, then you could run the cable overhead. It will need support and the traditional way to do this is to hang it from a tensioned catenary wire. For a short distance you can get away with using galvanised steel conduit, perhaps up to maybe 1.5m or so. The conduit will need an earth if run overhead like this, but that's easy enough, just use a normal earth bond clamp at one end with a run of 6mm² CPC.

One question, is the present 2.5mm² really protected by a 40 A fuse? If so, then that needs sorting, as it's far too high a rating to protect that size cable. Could it be that the garage CU has a 40 A rated RCD, and that the cable is protected by something like a 16 A or 20 A MCB in the CU supplying it?
 

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As indicated, if the power entry to the house is via a standard outside wall meter box, and it's suitably located, then the best option can sometimes be to split the feed after the meter to a new mini CU inside the box if there is room and then run the new cable to the garage from there. Leaving the existing garage domestic supply alone. If digging is unattractive, and as the garage appears to be only 1.5 metres from the house, then a high crossing via galv conduit would work as mentioned by @Jeremy Harris. Just don't forget about it when carrying ladders via that passageway. :(
 

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Discussion Starter · #8 ·
Guys thanks so much for all replies. Having read what you’ve said, I think the feed to the garage might already be coming from some tails off the meter - the existing 2.5mm2 cable comes out of a little grey wall mounted box just below the meter box.

cool - I’ll get some quotes for some works
 

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Discussion Starter · #9 ·
Hi guys.

Next question - sorry!

I got my results back from a remote survey and the installer said that given there is room in my meter box, and its location, then they would split the feed and put a new mini CU inside the meter box (just as Hitstirrer suggested above - thanks!) and run the cable to the EV charger from there. On the picture I have attached, the cable routing that they have quoted for is drawn in orange.

What I’m wondering is, could I ask them to follow the cable routing drawn in blue, into the garage wall and out again behind the Andersen, so that I get the floating look? Would they be allowed to bury the cable under the grey gravel between the cobbles and the path?

Thanks in advance guys.
145543
 

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Looks dead easy to run the cable up and over the path, along the top of that doorway. I wouldn't bother trying to go underground in those circumstances at all, makes the job harder and would cause far more disruption. Might still be an idea to run the cable in a bit of galvanised conduit, but frankly if that door/gate opening is sound then I wouldn't bother. There's no premature collapse concern with this location, as it doesn't look to be on an internal fire escape route to me. If there was, then a bit of conduit would address that.
 

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Discussion Starter · #11 ·
Thanks very much Jeremy. I’d prefer the cable to go under rather than over (it would be very noticeable across that beam above the gate). So I guess my question is… that grey gravel (where the blue line is) covers a trench that is about 10cm deep. Could the cable run through galvanised conduit underneath the gravel?
 

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Thanks very much Jeremy. I’d prefer the cable to go under rather than over (it would be very noticeable across that beam above the gate). So I guess my question is… that grey gravel (where the blue line is) covers a trench that is about 10cm deep. Could the cable run through galvanised conduit underneath the gravel?

Yes, with the proviso that it is going to be a real bugger to get the sort of minimum bend radius on the cable at either end. 6mm² SWA can't be bent at anything like a right angle, it needs to be swept in gentle curves, and that may make it difficult to fit neatly at such a shallow depth. I'm not sure that it would fit inside 25mm galvanised conduit with the sort of standard bend radius from a normal bender at either end, might need a bit of trial and error.

It would be within the regs to use NYY-J rather than SWA if mechanical protection is provided by steel conduit, and NYY-J is a bit easier to bend than SWA. One snag is that, for some unknown reason, some installers are averse to using NYY-J. No idea why, as it's easier to use, is rated for use outdoors, underground, even buried in concrete, so it's perfectly acceptable for most installations, especially as the cable will be RCD protected at source anyway.
 
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