Adding a small consumer unit

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We are combining two cottages, one of them really small, into one house. The little cottage has an old distribution board and meter plus company fuse. There are only four circuits - two small power rings and two lighting, with a maximum estimated load of 12.5 kW (we are putting the "laundry" in this part of the property.

I have already bought a Wylex 17th Edition ten-way insulated CU for the larger cottage (potentially eight circuits) and propose taking a heavy-duty link from this unit to a mini unit (say five-way) in what was the little cottage, thereby doing away - courtesy of NEDL - with the second meter, mains input and company fuse, and ill-assorted bits and bobs from 50 years ago.

Could I put a 50A MCB in the main CU and take a feed to the mini unit via a 10mm T&E (about 22m distance)? Would that be legal and safe (using an accredited sparks, naturally, to supervise and sign off the work). Or would the answer be to fit a separate 63A RCD to the large unit and feed from that?

Any advice and suggestions very gratefully received.

Many thanks

Ian40
 
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You'd be better off using SWA - more expensive than twin and earth but you won't need to faff about with steel conduit and as it has an earthed armour it is exempt from the need for RCD protection so you could safely connect it to a 50A MCB and then have the RCD at the cottage end - this will save you having to walk back to the main CU should it trip.

You seem to be a bit confused regarding the need for a registered electrician. Either you do the work and get building control involved, or you get an electrician to do the work - electricians can not sign off work they did not do.
 
electricians can not sign off work they did not do.

why?

Because thats not the correct procedure to follow. Electricians that are registereed to self-certify the work that they do should not be going around certifying work someone else did. There is a procedure set out that allows DIY'ers to carry out electrical work and get it inspected and tested, but that doesn't involve electricians, it involves building control.

Yes, there are times when electricians will sign off on work done by someone else, such as when it is agreed with the electrician, all the cables are kept on show, installed exactly as described and the electrician does the 2nd fix, but the number of electricians who will want a job where they just design something, let the householder do all the work, and then come and put their name to it, I would imagine is pretty low due to the high chances something will be done wrong, or atleast not to a sufficient standard.
 
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Would a machanic sign of work on brakes they let their junior do?

I work with aircraft. There is often a large team of mechanics, with only one licensed engineer per shift. Only the licensed engineer can sign anything off.

Do you think he thoroughly checks the work of 20 people?
 
Would a machanic sign of work on brakes they let their junior do?

I work with aircraft. There is often a large team of mechanics, with only one licensed engineer per shift. Only the licensed engineer can sign anything off.

Do you think he thoroughly checks the work of 20 people?

That said I assume the juniors working on aircraft are already highly qualified which is more than can be said about the oinks at those fast fit centres that don't know their camshafts to their propshafts.
 
I work with aircraft. There is often a large team of mechanics, with only one licensed engineer per shift. Only the licensed engineer can sign anything off.

Do you think he thoroughly checks the work of 20 people?

I would bloody well hope that he checks the work sufficiently to confirm it is safe, and if he doesn't he needs a kick in the *******s and to be shown the door.

Regardless, there is still a big difference between your scenario and this one. If the other people doing the work are mechanics then its safe to assume that they know what they are doing and only require basic checks by the supervisor. If you replaced those mechanics with random aircraft passengers would you then feel happy signing off on the work?
 
Ian40 said:
We are combining two cottages, one of them really small, into one house.

Do you have two separate buildings here, necessitating a cable run outside? Or is that 22m just the distance between the two existing CUs in what is now a single building? :confused: :confused: :confused: In the second case I'd be inclined to rewire the circuits from the small cottage into the new CU for the big one. :idea: :idea: :idea:
 
got to disagree on this one, i know loads o sparks quite happy charging just to sign off work (granted i think most of these are one week wonder sparks picking up extra few quid)
not saying i agree with it just making point that the whole system is a joke.

I do a lot of work (non electrical), for a builder who decided to do a week disq course, now according to napit he just got his full scope - no previous exp or training one week £1000 and off you go now hes making nice money signing work off for everyman and his dog and doesnt know an ohm from a banjo and thats the one example.....
 
Thanks for all the helpful responses. I didn't expect to provoke a discussion on the vexed question of delegated responsibility, and of course I wouldn't dream of soliciting the technical endorsement of an electrician who hadn't been involved from the start in a project. I will, in all likelihood, consult local Building Control anyway.

In answer to two questions and with a further couple of mine: 1) there is no requirement to take a cable outside or through walls; the cabling will pass beneath a now-common joisted wooden floor; 2) the small cottage was rewired about five years ago (albeit from the antedeluvian distribution board) so it would be cost-ineffective to re-rewire from this end of the property into the new Wylex 10-way at the main end of the house. And since I have a new 5-way unit, I'd prefer to wire to that.

The questions then resolve themselves to these: 1) do I need an RCD at the cottage end, or can I link straight from a 50A MCB (in the big split-load RCD Wylex) to the main switch block in the mini CU? And 2) can cable or SWA for this purpose be laid beneath my floor with simple clips - or must it be conduited or other wise special-protected?

Again, my many thanks for your responses.

Ian40, Hexham
 
Since the total load over the 2 properties is under 100A why not terminate the service tails on a Henley and run a set of tails to the primary consumer unit and a SWA of suitable size to the 2nd CU.
You should also consider having 2 x on / off switches to isolate the supplies before the CU so that the CU's can have total isolation should further work be carried out post the main install.

Then your have more flexibility and better load potential than the 50A restriction you have designed in to your suggested method at the 2nd CU.

SWA needs no further protection and if under the floor can be loose laid on the ground. If the ground is likely to suffer from wet / damp then fix to the underside of the joists.

The 2nd CU should still have a RCD to add protection since you are unlikely to find that any cabling is >50mm in to the walls.
 
We've just done a similar job with a new CU in an extension. I involved both building control and my electrician. The electrician took double insulated tails (and earth) from the connector blocks (Henleys?) into an insulated enclosure with a 100DP isolator. From there was fitted directly below a metal box allowing the secure connection of the SWA (16mm in our case) and the conductors into the isolator enclosure

In the extension, the SWA was terminated in another metal box, directly adjacent to the new CU and the 16mm conductors taken through into the CU

The building control officer was content for me to wire the CU and extension under the guidance of the "Select" electrician. I laid the SWA under the floor and the electrician connected both ends and visually inspected my work and conducted and certified what I believe is Periodic Inspection Report for small works. He was therefore not asked to certify the installation which would have been unfair and we arrived at a pragmatic solution.
 
If a qualified electrician can only sign off his own work then there would be hardly any buildings with test certificates of course an electrician can sign off peoples works if he/she is qualified and proven to reconised industry standard
 
You are wrong. An electrician who is a member of a self-certification scheme can not issue a building regulations compliance certificate if they did not carry out the work. You can issue an EIC for which you only complete the I&T section or a PIR but that does not mean anything with regards to Part P compliance.

I'm not sure on other self-cert schemes but here's a quote from NAPIT...

NAPIT said:
Can I notify a job if I carry out the electrical inspection & testing?

Approved Document P is quite clear that a scheme member can only self-certificate (in other words notify the work through NAPIT) if they have carried out the installation work (clause 1.19). All other routes involve the work being notified to a building control body (the local authority or an approved inspector) before work starts. From that point there are still two ways in which a NAPIT member could be involved.

Clause 1.22 allows an unregistered installer to submit the BS7671 installation certificate and says that the building control body will take this into account. If an appropriately qualified NAPIT members has carried out third party electrical inspection and testing for such an unregistered installer then they can complete the BS7671 installation certificate providing they follow the advice given in the question & answer above and only sign off the inspect and test element. The member cannot notify the job in this case.

Clause 1.26 allows the building control body to contract out inspection and testing. It is clear that the building control body must pay for this work and cannot require the householder to pay. In this case building control bodies would normally appoint a member of a Competent Persons Scheme. Again, the member cannot notify the job in this case.
 

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