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?

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?