OpenEVSE and wiring regs changes (722.531.2.101)

Thanks for putting us onto this. We are looking at options to integrate compliant DC leakage detection. The bender unit looks very interesting. Another options is Type A Residual Current Devices | Emobility

Type-B RCD’s with 6mA DC detection are expensive. I am able to obtain Chint NL210 RCD unit with 6mA DC detection for approx £130.

Good idea, I will put together a guide.

Indeed, your right about the Renault Zoe having a tighter requirement for earthing. I’ve also heard the 150 ohm figure being mentioned although I’ve struggled to find an official figure from Renault. Apparently using CanZE Android app + ODB2 Bluetooth dongle it’s possible to obtain lots more data from the Zoe, apparently the Zs reading is displayed on can bus when starting a charge and can be viewed using CanZE. I’m afraid I don’t have access to a Zoe to test this. I am however aware that I’ve never had trouble starting a charge from older public charge points in my LEAF, while PlugShare / ZapMap is full of comments from Renault owners unable to charge.

Ah yes, I’ve watched that. John is a legend!

You’re totally right, the current system was designed for residual AC monitoring. Sorry for the confusion. We recently had the unit tested using an RCD tester and the unit tripped at 15mA DC leakage. This reading is irrelevant since is nowhere close to the required 6mA.

I’m happy for this to be discussed on this thread since it’s applicable to 17th edition wiring. Are you referring to PEN fault detection? The EmonEVSE currently has got loss of earth detection but not PEN fault (protective earth and neutral) detection. Therefore, an earth-rod is currently required for outdoor installations, or where the EV under charge is located outdoors.

To comply with PEN fault detection if the voltage between the protective conductor and earth electrode is 70V rms we would need to disconnect the protective conductor from the EV within 5s. This would require an extra contactor to disconnect the protective conductor. This is something we’re considering integrating in future revisions. Currently, the recommended way round this is to install an earth rod (TT Island) on PME earthing setups and don’t use the PME earth.

Excellent to hear the RCD / 18th Edition issues are being looked into :smile:

I have to say I think 722.531.2.101 is not well thought out.
Why is it only EV chargers with the 6ma DC restriction. What about anything with possible DC faults (PV or even DC power supplies). They only need a few mA DC leakage to make RCDs/RCBOs inoperable.
Solving the very low probability of the failure of the PME system with a TT island is also a bit bonkers. I remember last century when we switched from TT to PME because house earth rods were susceptible to corrosion/lack of maintenance/damage etc.
Voltage operated protection was commonplace but considered inferior to RCDs when they came in.
Anyway, a bit off topic.

Maybe not
See Pod Point’s installation guide at

The new Pod Point Solo features an on-board safety
monitoring system to detect low voltage supplies and
potential earth-neutral faults, If such a condition is
encountered the charge cycle is ended or prevented and
the Pod-Point effectively becomes a double insulated
(class II) device. The vehicle becomes isolated from the
incoming supply and poses no risk to touch.This feature
removes the requirement for an earth electrode where
it may be ineffective or introduce further risk. The Pod
Point Solo unit (tethered or socketed) may be connected
directly to a TN-C-S (PME) earthing system without any
special arrangements, the new Pod Point solo complies
with regulation 722.411.1 (iii) of BS7671: 2018.

Also, if you talk to MyEnergi about the (long long overdue) Zappi 2 they also say they need no earth rod.

I for one would consider the risk of PME failure much lower than a domestic TT island’s earth rod failing so the Pod Point/Zappi solutions would be preferable.


I just want to charge my Leaf with my PV without mucking about with an expensive type B RCD and a TT earth rod…
I’d love an OpenEVSE sytem 'cos I love to support community activity
Whitby Esk Energy Community Hydro

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Hi Glyn

I’ve just had a thought about that.
I can’t see anything in the circuitry that checks DC so why do we think the unit tripped at all?
AFAICS the only residual current sensor is the CT and that would saturate and provide no voltage to the GFCI circuit.
Was the test pure DC or half wave AC?

Without knowing the technical details of these units, my guess is they have integrated GND disconnect contactor to isolate the EV if a PME fault occurs. I agree this protection mechanism is superior to a TT island but obviously requires hardware changes. It’s something we’re looking into for future hardware revisions.

I would also like to learn more about this. I will obtain more info and get back to you.

Forgive me for jumping in on the end of an interesting discussion (and for being a bit of a beginner)

I was planning to install a Zappi-2 (when/if it becomes available) but after many promises of an end user API over the last year my hopes were finally dashed with an email from one of their directors confirming they will not be developing one so I have cancelled my deposit.
Looking for alternatives I came across your EVSE which ticks all boxes but this thread concerns me.
I have a TN-CS site. While £550 is a saving over the Zappi, adding a £300 type B RCD is a bit of a sting in the tail. Is this just something I have to accept or is there any other option?
Apart from the RCD issue, is there a reason why your EVSE steps up and down in 1A steps? The Zappi seems to follow the export CT to within about 50W. Here I am going to expose my ignorance about the PWM signalling but is this something that can be improved in future?

Hi Steve,

I’ve just been in communication with our OLEV installer and their electrical supplier. They use a Chint NL210 Type-B RCD which meets the requirement not to be blinded by 6mA of DC leakage. This RCD costs less than £120. We will be getting stock of these RCD’s to sell with our units in the next week or so.

If you are interested in getting an EmonEVSE unit installed under OLEV I would recommend contacting EcoPlugg for a quote.

We are working on integrating DC leakage detection into our unit, but this is probably about 6-12 months away and will probably add about £100 at leat to the cost of the unit.

1A control resolution is the J1772 protocol supported by all EV’s. Zappie or any other EVSE won’t be able to control the charge rate at any higher resolution since this is a hard limitation of all EV’s. Also the minimum charging current of J1772 is 6A approx 1.4kW.

For more info on J1772 see: OpenEVSE SAE J1772 Theory of Operation : Support

Thank you for the fast response Glyn. I certainly will look out for your affordable type-B RCDs. Will they appear on the shop as optional accessories? Sadly I cannot take advantage of the OLEV grant as I have used my allocation, first with a PodPoint five years ago and the second time with a Zappi about two years ago.
The Zappi really does manage higher resolution changes, certainly with the Golf and the Kona we run here but it isn’t a huge issue as we now have a couple of Powerwall IIs which can absorb/support the gaps. It may be that some cars go beyond the J1772 PWM standard although I concur with the 6A lower limit. That is where the Zappi cheats a bit, allowing you to set a %age of “greenness” permitting EVSE startup when PV is <6A.
I’ll temporarily disable the batteries the next time we get a sunny day and plot the PV against the export and post it here.
I have never tried playing with MQTT so am looking forward to control the EVSE max rate based on the PWs SoC and the Octopus HH tariff.

Yes, hopefully in the next week. I’m just waiting on supplier to finalise pricing.

Actually, I think you could be right. The PWM could be controller to a higher resolution. The limiting factor would be the onboard charger. I will do some testing and investigate if the openevse controller could in the future be firmware upgraded to support higher resolution.

Yes, there are lots of possibilities for automation and integration. Using NodeRED is a popular option.

Hi all
Came across this link
Voltimum news
Which states

From January 2018, IC-CPDs manufactured to IEC 62752:2016 used in Mode 2 charging cables , had to include the facility to detect DC residual currents and disconnect if > 6mA DC

This would make it difficult to sell plug-in versions of OpenEVSE without the type B rcd.

Look forward to £120 rcds as I can only see them over £200 :grinning:

Interesting, thanks for the link. The OpenEVSE is not sold as a mode 2 unit. We are working on integrating DC current leakage detection. In the meantime we have sourced some reasonably priced type-B RCDs:

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Apologies in advance, if my post doesn’t make any sense.
Like many others I have been looking at openEVSE as an option, but worry about the need for TT island’s earth rod.

I noticed this article about amendments to the 18th edition, which I am sure you are very well aware:

Is this something the OmonEVSE unit is likely to support?

We are investigating EmonEVSE hardware upgrades to negate the need for an earth rod, however I cannot give you a time frame on this.

If an earth rod installation is not possible, a Matt-E device to provide an earth disconnect under fault condition:

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Hi, is it correct to say that to comply with new regs (18th ed. amendment 1) openEVSE outside should be installed with:

  • Type B RCD and Earth rods
    *Matt:e (or similar device like Garo G6EV40PME).

Should internal GFI be removed?

Hi @roberts
Short answer yes but not just outside. All EVSE now need to have open PEN protection whether inside or out.
The Matt: e or similar just removes the need for TT earth (rods).
You will always need the functionality of type B rcd (for DC fault protection). Some EVSE has this built in. As of last year OpenEVSE didn’t (but I’m not up to date with that)
I believe you don’t need to remove the internal GFI/RCD - why would you want to?
FWIW the Matt:e variant with type B rcd is the SP-EVCP-B

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I will follow this thread with interest given I’m in the market for a 3 phase EV charger

Thanks for the comment @EskEnergy - it’s nice to talk about those things with other people who are interested in electric vehicles!

I was asking about removal of GFI because I remember seeing somewhere a note to not to disconnect it. I was wondering if it plays a part in functionality of the equpment - e.g. check to allow charging to start.

Regarding other comments, there are few common misconceptions for domestic installatons I think I should address.

  1. “Open PEN detection device is required for all EVSE whether indoors or outdoors.”

Those devices are not a requirement in BS 7671:2018 (+A1 2020) at all. In fact 722.411.4.1. says that PME supply should not be usd for EVSE outdoors unless one of five conditions is met, where this Open PEN detection device is just one of the options.

  • If the vehcle is charged outdoors there are other options, for example, installing additional earth electrodes, converting existing installation to TT, TT system for EVSE only or isolation transformer.

  • Open PEN detecion device is never needed if the EV is charged inside and there is no posibility to use it while EV is outside. CoP 6.7.1. repeats that PME can be used within a building without rods (or open PEN devices for that matter), but gives aditional suggestion that non-extended tethered lead only should be used (key - you should not be able to be in contact with true earth and PME earthing).

  1. “Type B RCD is needed for DC fault protection”

722.531.3 specifies what type of RCD is needed for EVSE. That is:
*Type B RCD or
*Type A or Type F in conjunction with RDC-DD.

From my experience if Type B RCD is not installed, Type A RCD is used together with a residual direct current detecton device (RDC-DD) that can detect if the DC component exceeding 6mA and disconnect the supply. Those devices might be built-in in EVSE or can be installed seperatly.

  1. Regrding Discrimination.

In 18th edition it is called Co-ordination or selectivity. Yes, if you install RCD in your EVSE distribution board you might have issues with coordinaton with RCD/GFI. CoP recognizes that sometimes it might not be practicable to folow it. This is the reason why I was asking if GFI is required for functionality of the OpenEVSE.


I consider my wrist suitably slapped!

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I have managed to integrate the Western Automation RCM14-03 module into the OpenEVSE unit.

This gives AC 30mA and 6mA DC GFCI protection (tested and confirmed). While there are several methods of integrating the module…I wanted to simplify the integration so that DIY builders can easily upgrade their units without having to make modifications to the actual controller board or firmware.

The RCM14-03 gives a ‘HIGH’ output on its [FAULT] pin via a pull-up resistor when leakage is detected.

This [HIGH] signal can be directly coupled to the sensor input (pin 2) on the GFCI connector. The value of the pull-up resistor is selected (1k2) to level shift from 12V operating level to the 5V input of the GFCI detector.

I added an ‘exciter’ coil to the RCM14-03 so that the self tests will run without issue. I also made a custom cable with integrated pull-up resistor so that the module can be fitted easily to the controller board.

I received great support from the R&D department of Western Automation who are the manufacturers of the necessary modules.

Please see pictures attached.

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Just been reading this brilliant thread and would like to add that in the COP for EV 5.2.3 unless it can be guaranteed that the supply is TNS back to source, ie your own transformer. TNS should be treated as TN-C-S.