Any electricians here?

[forgotusername]

To save you reading the whole piece, my query concerns problems charging an EV because a circuit breaker trips.

I have owned a BMW i3 for about 5 years. I have an EO Mini wall charger mounted externally and have never had problems charging the car until recently. I put my car on an overnight timed charge (I specified when to start and stop charging). Using an app on my phone I saw that I was consuming about 8kw of power at 0100 hours and knew this meant the car was charging. When I unlocked the car in the morning, it made a "bong" sound and the charger port on the car was flashing orange, which I didn't understand at the time. As soon as I started the car, I could see that the range had increased by a mere 20 miles when I was expecting something more like 90 miles extra.

I recently had solar panels and battery storage installed by Infinity Renewables and Octopus replaced my non communicating SMETS2 meter. I elected to use the Octopus EV tariff which provides very cheap power from 00:30 to 04:30 and which I can program into my car charging options. On investigation, I found the circuit breaker for the EO charger had tripped. The main RCD had not nor had any other house circuits been tripped. The breaker in question is one of these:
https://www.tradesparky.com/circuit-pro ... a-30ma-6ka

I reset the breaker and put the car on charge for 15 minutes to see if it failed again. It didn't so I'm struggling to understand what might be the problem given that everything has worked perfectly for years and I can't see how recent changes would alter that.

I will probably get an electrician to visit but if it could be the work of the solar installers or Octopus who fitted the new Smart meter, I would expect them to fix it. If anyone has any ideas, please reply. Thanks.

[Sixtyone]

If it's only happened once I wouldn't worry about it, it may just be a nuisance trip and the cause will never be found.
If you do get it looked at I would ask if that RCBO is the correct type, Type AC is the general purpose one whereas Type A Double pole is typically used for EV chargers.

My knowledge is way out of date, so best wait for a expert.

[csearle]

To save you reading the whole piece, my query concerns problems charging an EV because a circuit breaker trips.

I have owned a BMW i3 for about 5 years. I have an EO Mini wall charger mounted externally and have never had problems charging the car until recently. I put my car on an overnight timed charge (I specified when to start and stop charging). Using an app on my phone I saw that I was consuming about 8kw of power at 0100 hours and knew this meant the car was charging. When I unlocked the car in the morning, it made a "bong" sound and the charger port on the car was flashing orange, which I didn't understand at the time. As soon as I started the car, I could see that the range had increased by a mere 20 miles when I was expecting something more like 90 miles extra.

I recently had solar panels and battery storage installed by Infinity Renewables and Octopus replaced my non communicating SMETS2 meter. I elected to use the Octopus EV tariff which provides very cheap power from 00:30 to 04:30 and which I can program into my car charging options. On investigation, I found the circuit breaker for the EO charger had tripped. The main RCD had not nor had any other house circuits been tripped. The breaker in question is one of these:
https://www.tradesparky.com/circuit-pro ... a-30ma-6ka

I reset the breaker and put the car on charge for 15 minutes to see if it failed again. It didn't so I'm struggling to understand what might be the problem given that everything has worked perfectly for years and I can't see how recent changes would alter that.

I will probably get an electrician to visit but if it could be the work of the solar installers or Octopus who fitted the new Smart meter, I would expect them to fix it. If anyone has any ideas, please reply. Thanks.

The RCBO will trip if there is an overcurrent for long enough or if there is a current greater than about 25mA leaking from either live wire to Earth¹.

As the arrangement has worked fine for a long time I would suggest that the selection of the RCBO is ok (well, ok enough to work). It could conceivably be down to the changes that have recently been made to the installation but my first suspicions would lie with the electrics downstream of the RCBO.

When an RCBO trips because of Earth leakage the cause is almost always (>95%) because of water ingress into the electrics. It might also trip because of an intermittent short-circuit causing more than 32A to flow². Both these issues could be caused by faults in the charging enclosure, the lead, the plug, or the car.

On the night it tripped was there a huge amount of rain and wind? You could switch off the offending RCBO and release the screws holding the enclosure lid on to inpsect it. There may be signs of water in it³. Same could be done to the plug.

That's where I would begin (well apart from testing the RCBO, but I imagine you haven't the kit.)

Chris
¹ Or, if there is a fast rise/fall of voltage on the RCBO's input. Electrical storms in the region? Was anyone arc-welding that night?
² Either a little more than 32A for a long time or a lot more than 32A for a little time (or somewhere in between).
³ If there is, let it dry and drill a small (say, 5mm) drain hole at the bottom of it. Also, see if you can see why it got wet.

[forgotusername]

Thanks Chris. Yes it was raining and from the SW which is the side of the car on which the charge port is located. As I implied, this orientation has never caused a problem before despite many "monsoons". I'm not sure I understand your point about the RCBO getting wet. It's inside my garage in the main consumer unit enclosure. Only the EO charger is outside, but it is exposed to wind and rain.

I charged the car again last night and all appears well at first sight, showing a full charge. I'll report any further issues if they occur. If weather is the cause I can park the car the other way round to shelter the socket and lead.

[Urbandreamer]

I'm not sure I understand your point about the RCBO getting wet. It's inside my garage in the main consumer unit enclosure. Only the EO charger is outside, but it is exposed to wind and rain.

I think that what was meant was "anything" connected to the RCBO getting wet.
Over decades I have had a number of such trips in the house.
The most common was a dehumidifier, Naturally wet. Fixed by replacing it.
After that was a steam iron. Fixed by replacing it.

See the common cause. Applications exposed to water.

By all means change the way that you park. That may be an effective solution.
Also nip out in the driving rain and see if it's driving into the wall unit, or running down the wall above.
Obviously check any guttering in the area.

[jfgw]

If you do get it looked at I would ask if that RCBO is the correct type, Type AC is the general purpose one whereas Type A Double pole is typically used for EV chargers.

My knowledge is way out of date, so best wait for a expert.

An expert hasn't responded to this so here's my offering:

Type A is now the general purpose one as it has some DC sensitivity. Those old AC ones can actually be inhibited by a DC fault and this "feature" was utilised by some of the old Robin PSC/loop testers: They introduced a small DC imbalance in the line and neutral which saturated the core of the RCD, rendering it ineffective and allowing loop tests to be conducted without it tripping. Since so much electrical equipment now incorporates electronics which could, potentially, develop an earth fault or cause a shock with a DC component, type AC RCDs are now rarely considered appropriate. A type A RCD provides the protection of a type AC but with the addition of protection against faults with a rectified mains frequency component.

In some cases, type A are not sufficient. Microwave ovens and inverter-drive washing-machines can produce frequencies other than 50Hz which can interfere with the operation of type AC and type A RCDs. A type F RCD is usually suitable in these cases. (The "F" stands for "frequency".) A type F RCD provides the protection of a type A but with the addition of protection against faults with different frequency components.

A type B RCD, in addition to providing the protection of a type F, also protects against steady DC earth faults. These are mostly needed in circuits incorporating three-phase rectifiers.

A type F RCD has the advantage in that it is less likely to nuisance-trip than a type A or type AC. This could be useful if you are prone to surges (for example, from lightening, arc welding, spot welding or Frankenstein experiments).


Julian F. G. W.

[Howard]

We have home charged a BEV for just over 3 years on an Octopus Go tariff. So about 100 charges from our 7kW charger in the garage. From memory, I would say that it has tripped the switch in the meter cabinet a couple of times and the charger has needed re-setting once. Like the OP this meant that the car received only a part charge. I reset on each occasion once I discovered the problem and the subsequent charge worked perfectly.

This happened with all the key bits in a dry environment. So our trips would suggest that your experience, forgotusername, might just be a random event caused by some vagary in the electricity supply?

regards

Howard

[csearle]

I'm not sure I understand your point about the RCBO getting wet. It's inside my garage in the main consumer unit enclosure.

As our Urbandreamer clarified, I wasn't trying to suggest the RCBO was getting wet but rather that either of the live conductors downstream of it may have done. That could happen for example in the charging enclosure. I'd switch it off at the RCBO, whip the lid off, and see if you can see any water build-up. Hope you (and any water ) get to the bottom of it!

Chris

[servodude]

I'm not sure I understand your point about the RCBO getting wet. It's inside my garage in the main consumer unit enclosure.

As our Urbandreamer clarified, I wasn't trying to suggest the RCBO was getting wet but rather that either of the live conductors downstream of it may have done. That could happen for example in the charging enclosure. I'd switch it off at the RCBO, whip the lid off, and see if you can see any water build-up. Hope you (and any water ) get to the bottom of it!

Chris

Totally agree that it's almost always caused by water (I think a very similar query popped up here recently).

[Urbandreamer]

By all means change the way that you park. That may be an effective solution.
Also nip out in the driving rain and see if it's driving into the wall unit, or running down the wall above.
Obviously check any guttering in the area.

Possibly I wasn't as clear as I should be.
The above was to identify a problem, not to provide the solution.

The solution could be as simple as changing the way you park or fixing gutters, but it might be as "complicated" as fitting something like this.
https://www.amazon.co.uk/s?k=rain+canop ... -doa-p_1_8
Or this, designed for the job but a bit ugly.
https://www.amazon.co.uk/Protection-Cha ... SVM34?th=1

[forgotusername]

I appreciate all the helpful suggestions here. I did as Chris suggested and turned off the breaker so that I could inspect to inside of the charger outlet. The plastic screws on the face plate are the sort that are retained when undone and are covered with rubber "bungs" which look in good condition. The face plate has a seal to prevent water ingress to the back box. There is a small hole at the bottom of the back box to act as a drain should water penetrate.
I checked for signs of moisture but found nothing untoward. I checked all the wiring connections and found nothing loose or capable of shorting on another wire.

I tried the "test" button on the breaker and it immediately switched off.

Perhaps the problem lies with the chart socket on the car which is more exposed so I'll see if it happens again and change parking orientation if it does.

[csearle]

I appreciate all the helpful suggestions here. I did as Chris suggested and turned off the breaker so that I could inspect to inside of the charger outlet. The plastic screws on the face plate are the sort that are retained when undone and are covered with rubber "bungs" which look in good condition. The face plate has a seal to prevent water ingress to the back box. There is a small hole at the bottom of the back box to act as a drain should water penetrate.
I checked for signs of moisture but found nothing untoward. I checked all the wiring connections and found nothing loose or capable of shorting on another wire.

I tried the "test" button on the breaker and it immediately switched off.

Perhaps the problem lies with the chart socket on the car which is more exposed so I'll see if it happens again and change parking orientation if it does.

Well done. Yes that does sound like the charger enclosure is ok. Sometimes getting to bottom of these things can take a long time, especially if the fault condition is intermittent. It is a lot cheaper to do all this preliminary stuff yourself and use the services of an electrician once the fault is reproducible.

Chris

[Urbandreamer]

I appreciate all the helpful suggestions here. I did as Chris suggested and turned off the breaker so that I could inspect to inside of the charger outlet. The plastic screws on the face plate are the sort that are retained when undone and are covered with rubber "bungs" which look in good condition. The face plate has a seal to prevent water ingress to the back box. There is a small hole at the bottom of the back box to act as a drain should water penetrate.
I checked for signs of moisture but found nothing untoward. I checked all the wiring connections and found nothing loose or capable of shorting on another wire.

I tried the "test" button on the breaker and it immediately switched off.

Perhaps the problem lies with the chart socket on the car which is more exposed so I'll see if it happens again and change parking orientation if it does.

Well done. Yes that does sound like the charger enclosure is ok. Sometimes getting to bottom of these things can take a long time, especially if the fault condition is intermittent. It is a lot cheaper to do all this preliminary stuff yourself and use the services of an electrician once the fault is reproducible.

Chris

Indeed. A point for the rest of us, forgotusername knows, unlike us, if it's a tethered charger or has a socket which the charging cable plugs into. It makes a difference when diagnosing the problem, as plug's and sockets are an obvious point where water can be a problem.

[Mike4]

I'm not an electrician but I fault-trace for a living. My own experience is that MCBs are more than capable of becoming unreliable and randomly tripping. When one keeps tripping for no obvious reason, replacing the MCB itself often fixes the problem. I wonder if the same applies to these newfangled RCBOs as they certainly look similar!

Also in the absence of any evidence about a fault a 'best guess' is always better than doing nothing. Doing nothing means the problem will persist but by having a guess and making a change, one at least loads the dice in favour of having fixed it by luck. My prescription is therefore, replace that RCBO.

(Speeling edit.)

[csearle]

I'm not an electrician but I fault-trace for a living. My own experience is that MCBs are more than capable of becoming unreliable and randomly tripping. When one keeps tripping for no obvious reason, replacing the MCB itself often fixes the problem. I wonder if the same applies to these newfangled RCBOs as they certainly look similar!

Yes well I agree. An RCBO is considerably more complex than an MCB and will therefore have a shorter mean time between failures. As for MCBs though, I think I can truthfully say that I've only come across a single one that has failed in my 18 years as an electrician. That one went open-circuit. C.

[Mike4]

I'm not an electrician but I fault-trace for a living. My own experience is that MCBs are more than capable of becoming unreliable and randomly tripping. When one keeps tripping for no obvious reason, replacing the MCB itself often fixes the problem. I wonder if the same applies to these newfangled RCBOs as they certainly look similar!

Yes well I agree. An RCBO is considerably more complex than an MCB and will therefore have a shorter mean time between failures. As for MCBs though, I think I can truthfully say that I've only come across a single one that has failed in my 18 years as an electrician. That one went open-circuit. C.

Really? I'm amazed!!!

I see it often enough to keep them as a stock item in my van.

[csearle]

I see it often enough to keep them as a stock item in my van.

I must have been lucky! C.

PS As we are no longer allowed to mix MCBs from different manufacturers in the same fuseboard the number of stock items must be quite large?

[Mike4]

I see it often enough to keep them as a stock item in my van.

I must have been lucky! C.

Or maybe the new-builds flats I see them in all used bargain basement consumer units!

Built on a shoestring, marketed as 'luxury', by and large.

[Mike4]

PS As we are no longer allowed to mix MCBs from different manufacturers in the same fuseboard the number of stock items must be quite large?

Blimey that's news to me.

But then I'm a feek plummer just trying to get people's heating or hot water back on. I doubt the regulations apply to me...

Seriously though, is this important? Does mixing brands actually present a real world safety risk? It sounds to me like one of those millions of regs that we have in gas world!

[csearle]

Seriously though, is this important? Does mixing brands actually present a real world safety risk? It sounds to me like one of those millions of regs that we have in gas world!

Well, between you and me I can't see it as presenting a problem very often at all. It's just that since the wiring regs change (of 2011 I think) we electricians, at least, are not allowed to "mix and match" as we used to call it. This is because altering the consumer unit means we have to issue a certificate, which we sign to say the changes are in accordance with the latest wiring regs.

The fraught reasoning is this I believe: consumer units are tested, as a unit, i.e. including MCBs, to BS EN 61439 (I think) to verify that, as a system, the mains service fuse (BS88 or BS1361) in combination with the MCBs can safely break 16kA/10kA (I think) of short-circuit current even if the individual MCBs are only specified to be able to break 10kA/6kA (I think). (Those figures might be wrong but I somehow can't work up the enthusiasm to find out for sure).

So by using the wrong manufacturer of MCB the thusly-altered consumer unit/service-fuse combo will not have been tested together. Hence it might not comply with the standard.

In reality it is not very often that the maximum possible short circuit current exceeds even 6kA (much more likely to be about 1.5kA). Maybe if the consumer unit were within 5m of a substation (which can happen, mostly in factories with their own sub-stations).

So we gave up that particular practice quite a while ago. C.