TESLA Charger Install - No earth

[Glan gluaisne]

TBH, whether the matt-e is compliant with the regs or not depends on what they have presumably agreed with the IET. They are selling the thing as being a compliant solution to avoid needing more expensive protection methods, so we have to assume that they have managed to persuade the IET that it complies with the voltage sensing method described in Section 722 of the regs.

The concerns I have are that this is a market where manufacturers have, in the past, played fast and loose with the regulations. Every grant funded charge point that has ever been installed was supposed to comply with IET guidance that was similar to that which is now in Section 722 of the current regs, yet the vast majority of charge point installers just completely ignored this. The daft thing was that anyone fitting a charge point before the 18th Ed of the regs came into force and who wasn't claiming any grant funding, could install a charge point with no special protection at all.

 

[Glan gluaisne]

@arg

My reading of the regs is that an installation that is protected by an RCD/RCBO of at least Type A, plus has touch voltage protection that complies with 722.411.4.1(iii) is OK if connected to an incoming PE, rather than needing a separate earth electrode.

The claim being made here is that the matt-e device provides protection that, from the description in the information in the installation instructions, seems to comply with 722.411.4.1(iii), although we've discussed this before, and I thought we were in agreement that it's hard to see how the matt-e device can comply with the 70 V max touch voltage requirement, as it doesn't have a local "true" earth reference.

Furthermore, my reading of the regs is that if a device complying with 722.411.4.1(iii) is used, then, as I mentioned previously, there is no requirement for a Type B or Type EV RCD/RCBO, using a Type A RCD/RCBO is all that is needed. Happy to debate this further.

 

[arg]

The concerns I have are that this is a market where manufacturers have, in the past, played fast and loose with the regulations.

I agree.

The really bizarre thing about the matt-e is that on their website they have a video explaining how the 3-phase model works, but in the middle of it they put up a slide (about 4:30 timestamp in the video) which says:


"Single-phase voltage devices do not work"
L-N voltage measurements do not offer a safe solution for detection in unbalanced 3 phase systems

The video then goes on to explain the issue very accurately, and around 5:40 the voiceover says:

"Single-phase voltage devices do not work"

Yet in addition to the 3-phase product (which I'm willing to believe is satisfactory), they also sell this single-phase product which in their own words "do not work"!


The video is at the bottom of this page on their website: Why do I need O-PEN?

 

[arg]

Furthermore, my reading of the regs is that if a device complying with 722.411.4.1(iii) is used, then, as I mentioned previously, there is no requirement for a Type B or Type EV RCD/RCBO, using a Type A RCD/RCBO is all that is needed. Happy to debate this further.

How do you read 722.411.4.1 to override 722.531.2.101? The latter seems to specify a very clear requirement for DC detection, and appears quite independent of which option was picked in 722.4.

Willing to be proven wrong, but I'm just not seeing it at the moment.

 

[Glan gluaisne]

How do you read 722.411.4.1 to override 722.531.2.101? The latter seems to specify a very clear requirement for DC detection, and appears quite independent of which option was picked in 722.4.

Willing to be proven wrong, but I'm just not seeing it at the moment.

TBH, I think you may be right, but Section 722.531.2.101 seems almost contradictory. It opens with this sentence:

722.531.2.101 Except for circuits using the protective measure of electrical separation, each charging point shall be protected by its own RCD of at least Type A, having a rated residual operating current not exceeding 30 rnA.

so if you stopped reading at that point you could be led to believe that fitting a Type A was all that was needed (given that the electrical separation method is impractical - no one is likely to want a 7 kW isolation transformer installed).

It then goes on to state this:

Each charging point incorporating a socket-outlet or vehicle connector complying with the BS EN 62196 series, protective measures against DC fault current shall be taken, except where provided by the EV charging equipment.

The appropriate measures, for each connection point, shall be as follows:

- RCD Type B; or

- RCD Type A and appropriate equipment that provides disconnection of the supply in case of DC fault current above 6 rnA.


RCDs shall comply with one of the following standards BS EN 61008-1, BS EN 61009-1, BS EN 60947-2 or BS EN 62423.

NOTE: Requirements for the selection and erection of RCDs in the case of supplies using DC vehicle connectors according to the BS EN 62196 series are under consideration.

which pretty much contradicts the first sentence, or at least seems to make it redundant, as it is not good practice to connect RCDs in series, without them having different trip thresholds (which they wouldn't have in this case).

My own charge point uses an RM014-03 AC/DC residual current module, together with a DP relay and two push buttons, one to test the unit and one to reset the relay on if it trips (so meeting the manual reset requirement). This was a cheaper solution than using either a Type B or EV RCB/RCBO, especially as I already 12 VDC power available to run both it and the DP control relay.

Interesting about that video from matt-e. It seems at odds with the statements from them in the installation instructions for their single phase EV charge point protection devices:

The wording seems a bit crafty to me. They state that the contactor complies with the current regs (and one has to ask why they bothered to write that), but they carefully don't state that the unit itself complies with any of the protection requirements given in the current regs.

As discussed before, I cannot see how this single phase voltage detection device offers any real degree of protection against the touch voltage exceeding 70 V under PEN fault conditions.

 

[bangtidy]

Hi Jeremy, I’ve been reading the other posts. And the ones above. So it seems like the Matt-e is compliant to the regs if interpreted a certain way? And the Voltage sensing fiction is a reasonable approach to safety. (I think so)

I was wondering should I get the bloke back to rip it out and ask for different install? ... but to be fair seems like the unit gives a lot more protection than if I got an EV Charing point installed a few years ago without any sort of contactor.

@Airbag80 - if you get chance, please can you let me know what voltage your car shows on its charging screen when it's pulling the full 32A. I noticed on mine that when it is working, the voltage seems to drop to about 217V which seems like a pretty big drop. Perhaps this is a clue as to why my matt:e is randomly cutting the power to the charger.

Also, after I reset my matt:e box, it seems to buzz quite a bit which doesn't seem right to me. Does yours do the same?

 

[Glan gluaisne]

@Airbag80 - if you get chance, please can you let me know what voltage your car shows on its charging screen when it's pulling the full 32A. I noticed on mine that when it is working, the voltage seems to drop to about 217V which seems like a pretty big drop. Perhaps this is a clue as to why my matt:e is randomly cutting the power to the charger.

Also, after I reset my matt:e box, it seems to buzz quite a bit which doesn't seem right to me. Does yours do the same?

That seems like a hefty voltage drop, depending on what the voltage is when there's no load on that circuit. UK mains voltage tends to sit around 240 VAC, although the nominal voltage is 230 VAC, +10% -6%, so the range can be anything from 216.2 VAC up to 253 VAC. Worth checking the voltage at the charge point end of the cable when off load, to see if you just have a low supply voltage, or if the voltage is being dropped either in the cable, or possibly by one or more connections that aren't properly tightened up.

Do you know the size and length of the cable from the incoming supply to the charge point?

It should normally be 6mm², which would give a voltage drop of about 0.217 V/m at 32 A, but if 4mm² cable has been used then the voltage drop will be higher, about 0.32 V/m at 32 A.

 

[bangtidy]

Do you know the size and length of the cable from the incoming supply to the charge point?

I don't I'm afraid but will take a look tonight.

We have heavy cabling that goes from the house meter to a 100A fuse in our cellar (approx. 5m). Photo below, the cable to the garage is the big black one coming out of the top of the 100A fusebox on the left:-
.

The heavy duty armoured cabling then goes under the drive in a duct to the garage (perhaps 20m) and into the back of a pair of consumer units.

From the consumer unit, the electrician has installed some new cabling across to the matt:e (approx. 5m in length) and then some armoured cabling from the matt:e into the bottom of the charger unit (approx. 1.5m).

I may be wrong but I'm reasonably confident that when the car was charging at 10A from a normal plug, the voltage was 230V and when I set the car to only draw 10A from the new charger, I'm sure the voltage was lower ie. hovering around 218/220V. I need to double-check this tonight but if that's the case, presumably that would point to it being some kind of issue with with the matt:e/charger installation rather than the supply to the consumer unit from the house?

 

[Glan gluaisne]

That looks to be a hefty run of SWA from that fused switch, so I doubt that there would be much of a drop on that run, even if it is around 20 to 25m of cable in total.

It may just be that you have a supply voltage that's at the lower end of the allowable tolerance, and that, plus a small voltage drop when you're drawing a steady 32 A from the charge point is enough to bring the voltage down to the 217 V the car is showing. Also, we don't know for sure how accurate the display in the car is, there could be a volt or two or error in that.

The matt-e is just some form of voltage detector, so if the voltage it sees drops it may well trip out. It seems possible that the low supply voltage/voltage drop that you're getting may be what's causing it to trip.

 

[bangtidy]

Thanks Jeremy, I'll do some checks tonight. It's happened even when limited by the car to 10A while the standard mains socket charger has been rock solid - I'm hoping that it's something with the install that's easily fixed vs. fundamental problems with the supply voltage itself.

Kind of wish I'd gone for a simple earth rod into the ground now but the installers weren't really interested in going that route as presumably it's just more hassle for them.

 

[UrbanSplash]

At 32a from the Tesla wall connector my car shows 237v

 

[Airbag80]

@Airbag80 - if you get chance, please can you let me know what voltage your car shows on its charging screen when it's pulling the full 32A. I noticed on mine that when it is working, the voltage seems to drop to about 217V which seems like a pretty big drop. Perhaps this is a clue as to why my matt:e is randomly cutting the power to the charger.

Also, after I reset my matt:e box, it seems to buzz quite a bit which doesn't seem right to me. Does yours do the same?

So I’ll check.... but, need to get my M3 first to test under load. I know when the guy installed it last week said that the unit tripped once... when he called the boys at matt-e they told him that 216V is the cut off of the unit. So I’m surprised your not having tripping issues. There is nothing in the Matt-e box that should cause a drop in voltage.

 

[bangtidy]

When you say 'tripped' do you mean the RCB tripped? That would be a bit odd for it to do that just based on low voltage I think.

Mine is definitely cutting the power to the charger when the volts drop below 216V and it's definitely dropping below that as the current draw ramps up to 32A but I've had it happen at as low as 10A and also not happen at all (once).

Not sure what I'm going to be able to do but it seems like this matt:e box isn't going to be any use to me and presumably they'll have to install a ground spike instead. Having it randomly cut the power like this makes it completely useless.

Another odd thing with the matt:e box is that it makes an horrendous buzzing after I turn it off and back on again following it having cut the power. A friend of mine reckoned it was a 50Hz buzzing so presumably related to the AC frequency.

 

[Glan gluaisne]

I think the reference is to the voltage sensing part of the matt-e tripping out, and needing to be reset by powering it off and then on again (which isn't compliant with the regs, either, it should not reset if the power goes off, but should require positive intervention).

 

[bangtidy]

So I've got the electrician coming this morning to take a look but as a test, I put some demand on the house's supply (51A) and checked the AC mains voltage at a plug. With little to no demand, it was 230V, under the 51A load it dropped to 217V.

My guess is that hour supply to the house itself could be the weak link. We are quite rural and our house is about 100m from the DNO's transformer (suspended between two telegraph poles) which I think is where our connection comes from.

Assuming that's the case, I'm guessing the matt:e box isn't going to be any use and we'll have to get an earth rod put into the ground?

 

[Glan gluaisne]

You may be able to get the DNO to increase the voltage a bit by changing the tap on the transformer. Whether they will do this or not depends very much on the voltage at the transformer and that supplied to other properties from it. The lower limit of the supply voltage is 216.2 VAC, and they have an obligation to keep your supply above that voltage, and below the maximum of 253 VAC. The fact that the voltage was already a bit low, at 230 VAC, with no load, and dropped to 217 VAC under a 51 A load, suggests that the supply outwith your property might be either already heavily loaded, or that the transformer is set on a fairly low tapping.

The DNO can change the LV supply voltage in 2.5% increments with the tap changer, although they are often very reluctant to do this. I have the opposite problem, in that our supply rarely drops below about 245 VAC and often exceeds the 253 VAC upper limit, and this then shuts down our PV inverter. I've been trying to get the tap changed on our transformer for well over a year now.

 

[bangtidy]

Thanks Jeremy, useful info as always.

 

[bangtidy]

So, replacement matt:e fitted and still have the same issue although the really loud buzzing of the first matt:e box has gone so that's good.

It seems pretty clear from some more testing that our supply voltage is low enough under load that using the matt:e box is going to be a problem. I'll contact the DNO to see if anything can be done.

In the meantime, I'll see if I can just run the charger at 16A or 20A rather than the full 32A. Especially given that the mains socket I've had the smaller charger plugged into has developed a big crack - presumably from the weight of the charger and possibly some heat build up. Definitely don't want to be using that socket any more.

If the DNO can't/won't do anything, another option suggested by the electrician is to remove the matt:e completely on the basis that the car will only ever be charged indoors however he would only do that if we also relocated the charger to the back wall of the garage (it's currently by the door) so that the charger cable can't physically reach outside and fitted a suitable RCB (type B?) between the charger and consumer unit.

This latter option sounds good to me as it removes the matt:e from the equation completely but will it still be safe and comply with regs? My understanding is that it would but perhaps I'm wrong on this.

Hopefully though, the DNO can just wind up the voltage.

Have to say, this is all stuff that I just didn't consider when ordering an EV!

 

[MrBadger]

Have to say, this is all stuff that I just didn't consider when ordering an EV!

Yep, just when you think you found your way out of one rabbit hole, you start to find yourself falling down another...

 

[Glan gluaisne]

So, replacement matt:e fitted and still have the same issue although the really loud buzzing of the first matt:e box has gone so that's good.

It seems pretty clear from some more testing that our supply voltage is low enough under load that using the matt:e box is going to be a problem. I'll contact the DNO to see if anything can be done.

In the meantime, I'll see if I can just run the charger at 16A or 20A rather than the full 32A. Especially given that the mains socket I've had the smaller charger plugged into has developed a big crack - presumably from the weight of the charger and possibly some heat build up. Definitely don't want to be using that socket any more.

If the DNO can't/won't do anything, another option suggested by the electrician is to remove the matt:e completely on the basis that the car will only ever be charged indoors however he would only do that if we also relocated the charger to the back wall of the garage (it's currently by the door) so that the charger cable can't physically reach outside and fitted a suitable RCB (type B?) between the charger and consumer unit.

This latter option sounds good to me as it removes the matt:e from the equation completely but will it still be safe and comply with regs? My understanding is that it would but perhaps I'm wrong on this.

Hopefully though, the DNO can just wind up the voltage.

Have to say, this is all stuff that I just didn't consider when ordering an EV!

TBH, I don't think that the matt-e device provides any useful protection, and I remain convinced that it does not meet the requirements in the regs. I don't think I'm alone in that view, either, as it seems that @arg may think the same way.

Assuming that the matt-e device does not provide the required level of protection the regs demand, then I'd say that the best option would be to install an earth electrode and suitable RCD/RCBO in place of the matt-e. That would definitely be compliant with the regs.

I also think it's about time that matt-e were challenged as to the apparent claims that fitting this device meets the requirements in the regs, without the need for an earth electrode etc. I cannot see how that can be the case, and as @arg pointed out earlier, there is a video on the matt-e website itself that makes it clear that voltage detection alone cannot provide adequate protection on a single phase installation.