Requirements for an electrical design & the EIC form signature

I would suggest in answer to your question sufficient information to enable the installer to complete the installation which is compliant with BS 7671. Enough information to satisfy the requirements of the CDM Regulations 2015. Enough information for the inspector to inspect and test the installation. 

For full design then to comply with RIBA Stage 4. 

I fully agree with JP (wouldn't dare do otherwise ? ) but any electrician who puts in any new work has designed it unless somebody else takes responsibility. That applies even to extending a circuit - is there spare capacity, is the Zs at the far end within limits and so on? Don't forget the wording of an MEIWC, part 5:

I certify that … and the work has been designed, constructed, inspected and tested …

The design needn't be written down - the information could be given verbally.

I have priced and completed jobs for builders where the architects have written an electrical work specifications including the sizes of circuit conductors and installation methods, I did seriously consider using a three part EIC and leaving the designer box empty rather than using a single signatory EIC.  

Chris Pearson: 
 

I fully agree with JP (wouldn't dare do otherwise ? ) but any electrician who puts in any new work has designed it unless somebody else takes responsibility. That applies even to extending a circuit - is there spare capacity, is the Zs at the far end within limits and so on? Don't forget the wording of an MEIWC, part 5:

I certify that … and the work has been designed, constructed, inspected and tested …

The design needn't be written down - the information could be given verbally.

But CDM Regulations still apply. Basically, whatever documentation you think is sufficient evidence if there's a proverbial knock on the door in future. 

Sure, extending a circuit could very well be something that shows the limits and extent of the work done, and document some inspection and testing (along with the fact that the circuit otherwise meets the requirements of BS 7671, the cable size and circuit length, and test results, say, fall within the limits of Table 7.1(i) of the OSG), I'd say that could well be sufficient design information.

Of course, you're also the contractor (and if it's domestic client, take on the Client's duties) … so perhaps some completion photos as proof in case anyone tampers with the installation in future wouldn't go amiss.

Any competent contractor should not implement a design that is obviously flawed. Further, the inspector should review the design and installation and so a third tier is in place to catch any serious infringement of BS7671 or statutory consideration such as CDM. 
We are far too wrapped up in ass saving in this country and unfortunately lose focus on the person who employed us in the first place, the client. 
Do all that is reasonably practicable,  that’s all that the law requires!

lyledunn: 
Any competent contractor should not implement a design that is obviously flawed.

That's a bold statement!

However, the designer certifies that he (she) has designed the installation i.a.w. BS 7671. The installer certifies that he (she) has installed i.a.w. BS 7671. So any installer must be capable of verifying that the design is sound.

I doubt that it works this way in practice.

Chris Pearson: 
 

lyledunn: 
Any competent contractor should not implement a design that is obviously flawed.

That's a bold statement!

However, the designer certifies that he (she) has designed the installation i.a.w. BS 7671. The installer certifies that he (she) has installed i.a.w. BS 7671. So any installer must be capable of verifying that the design is sound.

I doubt that it works this way in practice.

In part, “that's a bold statement” - obviously flawed is the operative words here though..

It kind of depends on the complexity of the design. Certainly if I imagine a big job - where the designer designs, the clients consultants approve, the main contractor takes on the job, the sub contractor(s) get to do the actual job, who's electricians and/or agency electricians do the actual job - how far down the chain does the electrician need to go to understand the design? 

On a big job - Just do what you are contracted to do. End of liability really. Theres the design, install that. If the 120th electrician down the line doesn't approve of the design, should work cease so we can review what that guy deems to be flawed? 

Clearly, I'd like to think the electrical engineer/install/contract Management for the Main contractor and at least the QS of the company that is doing the actual install might pick up on any design concerns, but not if its a little complex. 

In vague answer to the OP - Usually on a small domestic circuit job though, even if its a whole household new circuit install…………there's no specific design at all I'm sure - just install to already approved perimeters as shown in the on site guide and - voila - you'll be OK, the circuit(s) will be OK and everyone will be happy. 

As J.P. mentioned CDM - I know that CDM regs applies to any job, household or not, and that seldom gets considered on domestics. It seems to me, that most guys working on (occupied, especially) domestic premises would ask - health and safety? Whats that then? Design? What design?? Its a socket circuit/ light circuit, what design is there to do? As said above the on site guide already gives parameters under which designs would pass without further maths or considerations. 

If you install a Ring Final, who holds the design patent on the circuit? Not the installer, who is just adopting an already designed circuit type.

even if its a whole household new circuit install…………there's no specific design at all I'm sure - just install to already approved perimeters as shown in the on site guide and - voila

To my mind you still need to go through a design process even if using ‘pre-calculated’ circuits- after all someone has to decide weather a 32A ring, or a 32A radial or two 20A radials, or something else, would be best. All sorts of choices like that are surely part of any design process.

   - Andy.

I meant for this to discuss the practical requirements or outcomes that made an electrical design which would fulfil the design requirements for recording on an EIC.   There is a requirement for competence and legal responsibilities over design, having a design liability. 

As an example that got me thinking about this, I could give chapter and verse on a recent experience whereby an electrical contractor confusingly completed an NICEIC EIC to say that both they and an architect designed it and a second contractor I asked to confirm the also poor installation indicated that the M&E consultant designed it.   In my opinion, there was no electrical design at tender stage, only a consultants plan showing locations of lights, heaters etc. with a statement that it must comply with the IEE Wiring Regulations (yes it said IEE and not IET) so it was being left to the contractor to design the electrical installation itself.   

Surely a design has got to include at least the cable sizes, the circuit protection details by way of RCBO sizes and types, the containment details as sizes should also have been worked out etc.   

Paul