My war against dual rcd boards

Firstly the original lamp could of been filament or halogen or florescent/compact florescent the replacement surely by now will be LED thus the resistive load now becomes an electronic load with or without a certain amount of DC leakage.

How can you have any leakage from anything with a 2-wire connection, like a BC or ES lampholder? (and no other connection to terra firma).

   - Andy.

Sergio Fernandez said:

Firstly the original lamp could of been filament or halogen or florescent/compact florescent the replacement surely by now will be LED thus the resistive load now becomes an electronic load with or without a certain amount of DC leakage

Isn't that a matter for the product standards, and relevant legislation such as the Electrical Equipment (Safety) Regulations and the Electromagnetic Compatibility Regulations? A product manufacturer ought not to assume an electrical installation conforms to the current version of the national wiring code? They can, however, provide information and guidance for users and installers that highlight certain issues, I guess - but in the case of a general product with a standard plug, or a GLS replacement lamp, would the user even understand the information?

This debate about compatibility could go on and on in other directions. We do know that older RCDs (BS 4293 and BS 7288 prior to 2016) weren't necessarily tested for Electromagnetic Compatibility to the current levels - this could also be the case for RCDs to earlier versions of BS EN 61008 and BS EN 61009 than the current versions (although I haven't checked as of posting this) ... so are they safe for continued use if modern electronic devices are used in the premises?

AJJewsbury said:

How can you have any leakage from anything with a 2-wire connection, like a BC or ES lampholder? (and no other connection to terra firma).

Capacitive is possible in the cabling to the ceiling rose  ... but that would rule out DC, and would be generally low-level 'leakage'.

However, if the lamp is damaged, and the user is being protected against accidental contact with live parts, say after the rectifier, would the type AC RCD operate is perhaps another question?

Sergio Fernandez said:

I see no reason why a fully RCBO and SPD type2 CU can not be designed and installed in the average UK dwelling

I entirely agree, but I would not condemn a dual-RCB on those grounds.

In theory, any board to BS EN 61439 should be satisfactory.

My recent shopping shows me that I can buy a turkey from Waitrose or Tesco for over £100. Currently, Aldi are offering a small turkey with accessories for £12 - link. There is no reason to believe that the Aldi turkey is less safe or less nutritious than the Waitrose or Tesco ones.

So what is better about the Hager, or Eaton, etc. board. They might last longer, but how else could you justify the extra cost?

Chris Pearson said:

In theory, any board to BS EN 61439 should be satisfactory

Give or take selection of it in respect of and division of installation (Section 314), and appropriate protective devices (Part 5). BS 7671 applies to the 'selection and application of the equipment in the installation concerned' (see Regulation 113.1).

Chris Pearson said:

I entirely agree, but I would not condemn a dual-RCB on those grounds.

The point I was trying to raise was that in this day and age a new build dwelling or a major alteration of an existing domestic dwelling should have a fully RCBO with SPD type 2 CU used.  However designers are still using Split load CU for brand new installs in 2025.  As a casing point I visited a new housing developement in Hemel Hempstead last month and the show homes had split load CU’s.  The development is planned to continue building dwelling at that site for the next 2 years which I assume means that they will still be using the same split load CU at that site for the next two years.  In my opinion I would say the split load CU should no longer be marketed and sold in the UK for the average domestic dwellings.  

Sergio Fernandez said:

Can we assume they are type A RCD and not Type AC RCD

In my house, they are definitely Type AC. Been there for some time.

Sergio Fernandez said:

Can we assume there is also a Type 2 SPD and is fitted pre or post main switch

One is retrofitted pre main switch ... I also had SPD on the incoming copper broadband (previously broadband and phone) cable until very recently, as we'd had a couple of surge events during thunderstorms (low level cloud-cloud strikes probably capacitively coupled into the overhead telephone wires) that damaged electronic equipment in the house connected to the copper phone wiring. (SPDs were removed from "master boxes" from NTE 3  believe). However, this is no longer an issue, we have FTTP supplying broadband now.

Sergio Fernandez said:

In my opinion I would say the split load CU should no longer be marketed and sold in the UK for the average domestic dwellings.

I don't think that we are far apart, but as a libertarian, I would not ban them. They may have their disadvantages, but unless they are dangerous, their use should be permitted.

So let's propose a ban: what would the counter-argument be? It seems to me that it can only be economic, and trivial at that.

My argument in favour is libertarian - authorities (e.g. Parliament) should intervene in peoples' lives as little as possible, and people should be free to lead their lives as they see fit.

Apart from that and the economic argument, is there any other reason to favour dual-RCD boards?

In a fully RCBO CU each circuit has it's own (probably30mA) circuit.  Thus its own protection and no nuisance tripping affecting other circuits.  Some RCBOs may even be DP (Dual Pole)


I think designers need to stop looking at prices by companies like Wylex (Other brands are available) and start looking into what makes a better design.  In my personal opinion of engineering judgement a fully loaded RCBO is better than split load RCD and if the designers were open to reviewing their design then changing the housing estate/new development from lets say Hager Split load(other brands are available) to lets say Fusebox or Navitas not only would they save money but it would be a compliant install choice showing an attempt for future planning.  Eg should an electrician want to fit a Renewable/alternate energy source to the system.  
It seems that some Electrical designers are lazy and are happy for a rinse a repeat method rather than continuing to improve things. Designers need to think or be inspired more by the likes Percy Shaw, (cats eye) 

en.wikipedia.org/.../Percy_Shaw

I presume the rcd would still operate after all when we test we test on 0 and 180 which I assume to be positive and negative going cycles