TESLA Charger Install - No earth

[bangtidy]

I'm all for binning the matt:e box at this point. Would rather not have to get an earth electrode installed if I don't have to though so I'm thinking the easiest solution is to just move the charger to the back wall of the garage connected to a new Type A-EV or Type B RCD and then on to the breaker in the consumer unit.

If I can only ever charge the car inside the garage (it's 9m x 7m so no problems with space) is that still within regs?

 

[Glan gluaisne]

I don't think that having the car inside a garage makes any significant difference to the touch voltage risk, unless the garage floor is a sufficiently good insulator.

It's not normally much bother to install an earth electrode, maybe 20 mins or so to install and test, and the connection box at the top of the rod can be buried flush with the ground usually. My garage is detached and has a TT earthing arrangement, just because I didn't want to export the earth down ~30m of cable. I drove the rod down through the garage floor, just drilled a hole in the slab and then banged the rod into the ground beneath. I did this right near the wall where the garage CU is fitted, so there's a small box at the top of the rod and the cable goes up to the CU above.

 

[bangtidy]

I didn't want to drill through garage floor slab as presumably it would puncture the damp proofing layer?

Installing outside the garage would be possible although it makes things a little more fiddly as there are buried drains around the front and sides of the garage and doing at the rear makes routing a bit harder. The electrician didn't seem keen on the idea either for some reason - presumably just because he'd rather not have to do it.

I guess if I did install one, I'd probably want to make it the earth for the entire garage building.

At the moment, I can't say that I'm getting much in way of advice from the installer that I've already paid for the job.

 

[bangtidy]

I don't think that having the car inside a garage makes any significant difference to the touch voltage risk, unless the garage floor is a sufficiently good insulator.

10mm hard rubber interlocking mats so I guess these would do.

 

[Glan gluaisne]

10mm hard rubber interlocking mats so I guess these would do.

Yes, that will do!

 

[Glan gluaisne]

I didn't want to drill through garage floor slab as presumably it would puncture the damp proofing layer?

Installing outside the garage would be possible although it makes things a little more fiddly as there are buried drains around the front and sides of the garage and doing at the rear makes routing a bit harder. The electrician didn't seem keen on the idea either for some reason - presumably just because he'd rather not have to do it.

I guess if I did install one, I'd probably want to make it the earth for the entire garage building.

At the moment, I can't say that I'm getting much in way of advice from the installer that I've already paid for the job.

Installing earth rods seems to be something a fair few electricians are not that familiar with now. It used to be an everyday job years ago, when a lot more electrical installations used TT earth systems. I think part of the problem is this unfamiliarity with installing them, together with having to find a safe location, away from buried services.

 

[bangtidy]

I've got in touch with the DNO and they're going to try and get an engineer to visit today/tomorrow to check for under voltage.

That seemed a bit too easy so I'm not going to hold my breath on this one!

 

[Glan gluaisne]

I've got in touch with the DNO and they're going to try and get an engineer to visit today/tomorrow to check for under voltage.

That seemed a bit too easy so I'm not going to hold my breath on this one!

Massively quicker result than I've had from our DNO!

Fingers crossed that they may be able to change the tapping and give you a bit more to play with.

 

[thegruf]

this place is getting more like Screwfix sparkies forum but less argumentative
best hope that banallsheds doesnt get a Tesla ..

Seriously though - love it when you get such authorative well-researched advice on here

 

[Glan gluaisne]

best hope that banallsheds doesnt get a Tesla ..

God help us if he does and comes on here...

He is one, extremely good, reason that I do not post on a couple of electrician's forums.

 

[bangtidy]

Blimey that's good service - two guys from the DNO turned up at 7.30pm to take a look.

They took one look at the size of the cable into the house and the distance between the house and where it connects to the rest of the network and declared that to almost certainly be the issue meaning that if I want more volts, I'm probably going to have to get a cost for installing a new cable - which would probably involve trench work in the neighbours garden which I suspect wouldn't go down well.

However, they've also called in another team (tonight!) to come and check the state of things at the connection location as well just in case, but they think it very unlikely that there'll be any issue there.

Think I'm just going to have deal with the voltage drop.

Best service I've ever had from a utility though! All it took was one quick email to the DNO!

 

[bangtidy]

Definitely no easy fix from the DNO.

So, on the basis that I'm going to dump the matt:e and move the charger to the rear wall of the garage so that charging only ever takes place inside and is isolated via the rubber floor of the garage, I just need to think about what kind of RCD I need.

I've read the other long thread about them, but to be honest I'm still not quite sure what type I need.

The charger is connected to a 32A breaker on the CU. Am I best off purchasing an RCD Type-B or an RCD Type A-EV?

Any recommendations for something that's decent quality/value and this readily available?

 

[bangtidy]

This one perhaps?

Type B RCD / RCCB 63A for EV Charge Point Installations. 4 pole, 3 phase or single phase, 30ma, EKL1-63

 

[bangtidy]

Actually, this seems like what I need:-

Type B RCD + 2 MCB Garage / Mini Metal Consumer unit - EV Charge Point Install

 

[Glan gluaisne]

As you already have over-current protection in the form of the 32 A MCB, all you need is the Type B RCD, really. No need for another over-current protection device downstream of it.

 

[bangtidy]

Thanks Jeremy, do you think that one above that I've linked to (ie. the pair in the mini metal CU) will do the trick?

 

[Glan gluaisne]

You don't need the additional MCBs in that box, so a smaller box with just the Type B RCD will be fine, as you already have a 32 A MCB protecting the circuit from an over-current fault. You can get a smaller box like this: Metal Enclosure - 4 Module | ElectricalDirect that would take the 4 module RCD.

 

[bangtidy]

Ah sorry, I see what you mean now - thanks!

 

[arg]

OK, so most of the discussion above is now moot, as the updated regulations are now out:

Updates - Electrical

There's a new bit in the informative annex A722.4 which makes very clear that these line-voltage triggered devices don't meet 722.411.4.1(iii) .... but then there's a new 722.411.4.1(iv) which gives them free rein! Somebody's lobbying efforts paid off.

The stuff about RCDs (722.531.2) has been re-written, but I think with the exact same requirements as before, just that the requirement for 6mA DC protection is now described as an "RDC-DD complying with IEC62955".

There's also a change in 722.311.201 which I hadn't noticed in the draft changes, and which I think is now very poorly drafted. The requirement for a separate final circuit per chargepoint has gone (this is positive and gives more flexibility installing eg. a cluster of load-sharing Tesla WCs), the "no diversity" statement is gone (maybe obvious, but it was useful that it used to say so), and it now permits "manual" load curtailment, without saying what that means. Manual control by a change-over switch is sensible (and IMO was always allowed), but does this new clause permit for example a commando socket and a chargepoint side-by-side with just a notice saying only one to be used at once? Or even multiple chargepoints and a notice telling you to wind down the amps in the car if you use both at once? Or a sign saying "only charge the car when nobody's using the shower"? I don't think some of these are acceptable, but the text can be read to permit them.

 

[bangtidy]

I'm still trying to get my installer to come and take the matt:e box away. While he's offered to refund the cost of the matt:e he doesn't seem so keen to actually finish up the installation I've paid him for which is frustrating.

I've bought a type B RCD, 25m of 6mm cable, some cable clips and a small CU. I can see that I'm going to have to end up moving the charger myself and then just finding another electrician to connect and certify it all.

Ridiculous that I'll have ended up paying the other installer the best part of £500 and ended up basically doing it myself.