Alan B said:

In a presentation IET or NAPIT someone said that DC leakage comes mainly from the EV and not the EV charger point,

The main DC issue is to do with the pilot communication in the main ... an N-E fault will "blind" RCDs because of this functionality.

It's not necessarily the EV - it's the standard by which EVs handshake with char "charger" (correctly Electric Vehicle Supply Equipment, EVSE), or with a Mode 2 charging lead, the In-Cable Control Box (ICCB).

I'm not saying that potential faults within the vehicle itself, downstream of electronics, or due to switch-mode type operation, couldn't cause DC leakage current, just that there's a definite issue with the whole way that the pilot function in the BS EN IEC 61851 series of standards works, that makes DC residual currents an issue, even if you were to make the perfect "no DC leakage" electronic power converter in the on-board charger in the vehicle.

IronFreely said:

I made a video on this one as the installation company wanted “evidence” before agreeing to even look at it! youtu.be/NGPu7SP_bdc

It's a bit rough, but at least the polarity is correct. ;-)

The naked busbar is not nice, but is it non-compliant inside the wee DB? Presumably it should have a cover made from those lengths of plastic which stationers sell for binding like these.

Be careful with these videos - you have nearly revealed the location!

Interesting that Mike believes most new CU's being installed are no longer split load, house builders are still installing them as standard and will continue until they are banned.

Alan B said:

Interesting that Mike believes most new CU's being installed are no longer split load, house builders are still installing them as standard and will continue until they are banned.

Agreed ... a poor choice given the requirements of domestic installations going forward to support Solar PV, prosumer's electrical installations, EV charging, etc. etc.

This needs to be addressed at the Design, Selection and Erection stage.  I went to a Taylor Wimpey home about a month ago and they had installed a split load CU/DB.  The property was sold for over half a million pounds.  BS7671 needs to ban the use of the split load CU/DB in domestic arena.  It should be done in AM3 or 19th edition.  JPEL64 need to table this discussion.  Below are some points I listed elsewhere

I think in the average dwelling the day of installing Dual or split load RCD board has passed.  Lots still sold with type AC rather than type A minimum.

Personally I think the CU/DB in a dwelling should be full RCBO with SPD as a minimum.  There are so many reasons for this.  A Few below

Overload or potential overload of the RCD in split way

Nuisance tripping

More and more requirement for circuits to have their own individual RCBO (RCD)

Earth leakage currents soon adds up to the 30mA for that half of the board

Segmenting circuits to remove single or multiple points fo failure.  (EG downstairs lights on same circuit as outdoor PIR flood light, fast forward 6 months or a year and the PIR flood fails probably with moisture ingress and hey presto downstairs light fault)

If there is an RCD fault it takes out half a board so maybe 6 MCBs

The cost of an average RCBO for a dwelling is a few pounds so why not fully populate a CU with them rather than a dual split load board.  I went to a Taylor Wimpey home 6 months ago after handover and it had a split load RCD CU.  In that situation the installer has to follow the design which means that the installation designer need to be educated/convinced/forced by BS7671.  House builders are more concerned about the buy in price of the CU and install cost rather than the ongoing cost.  Imagine the electrician who goes in next week to find a fault and there is 1 RCD module covering 6 MCBs

I agree this needs to be addressed at design stage as with new build the installers literally don’t care about non compliances as it’s not their name on the certificate… in fact it’s unlikely the signatory will ever see the installation, they tend to receive test results from initial verification and if they match design calculations roughly it passes.

Looking at the specific problem of new builds being fitted with dual RCD boards with a provision for an EV… unfortunately they’re not necessarily guilty of a non-compliance as what tends to happen is they install an SWA cable on a 32A MCB which is terminated on the driveway in a wiska box… technically it’s fully compliant as it would only be non compliant when the charger itself is installed… in most cases the new property is sold with a provision for a charger rather than an actual charger being fitted.

Ive seen this a lot and unfortunately when I turn up to provide a quotation the clients are unlikely to be aware of 722.531.3.101 and so when the next person turns up and says they’ll be able to put the new charger straight on the existing circuit it seems like I’m just dressing up the cost of the job…. Bad for my reputation and a waste of my time, which is unfortunate as I’m the one quoting for a compliant job, this rarely comes back to the clients in any way…. I personally feel the only real life way to address this would be if notifications needed to include the installation certificate, this could be easily flagged up by a relatively unsophisticated peace of software which could detect such noncompliances and automatically refer it to the relevant competent person scheme for review. Is it not the point of the schemes to ensure competence and compliance?

Sergio Fernandez said:

BS7671 needs to ban the use of the split load CU/DB in domestic arena.  It should be done in AM3 or 19th edition.  JPEL64 need to table this discussion. 

How could this be done, considering that there is absolutely no reason why a board with a single RCCB (or split-load) couldn't be used in some installations ... a caravan, for example, because the supply it connects to has a 30 mA RCD as well?

A blanket ban on 30 mA RCDs feeding a number of circuits is really not a flyer for me - it would have to be another way.

Being a selection and erection issue, it would most likely have to go in Part 5 somewhere ... perhaps Section 536?

What would Forum Members like to see, and what are their ideas on how they would like to implement it?

A robust technical argument for the "ban" would also help things along.

Sergio Fernandez said:

Personally I think the CU/DB in a dwelling should be full RCBO with SPD as a minimum.

That is what I have done at home, so I can hardly argue otherwise, but the £1k DB may not be suitable for everybody.

what tends to happen is they install an SWA cable on a 32A MCB which is terminated on the driveway in a wiska box… technically it’s fully compliant as it would only be non compliant when the charger itself is installed…

Am I missing something here? Provided the EVSE has 30mA RCD protection included - which most seem to claim they do (presuming it does actually comply with the required standards, which has been questioned for one or two models) wouldn't 722.531.3.101 be satisfied even if the circuit was fed by an MCB?

   - Andy.

Hi Chris


If you put the install cost and EICR cost to one side for a moment the fully loaded CU/DB are about £200 from someone like FuseBox or Verso.  Personally I think the Verso kit is a better product.  

The offerings from Hager and Schieder will be more expensive.

The CUs can be supplied online from someone like

www.expertelectrical.co.uk

(other online sellers are available)

or at the local Electrical wholesaler like

Edmundson Electrical

(other wholesalers are available.)

Personally I would prefer a fully loaded RCBO with SPD Verso CU over a Split load/Dual RCD Hager CU.  I think the Financial aspect should take second fiddle to the better design, selection and erection that is offered by a SPD and fully loaded RCBO.