How does my DIY effort at a consumer unit look?

[RF Lighting]

The supply cable looks like a some 3core SWA (10mm or 16mm) in old colours

I would be interesting to see how the gland is made off.

The incoming was three 25sqmm in an armoured sleeve, which seemed a bit overkill for a small domestic installation. It came from a TN system, which I was able to isolate at another communal distribution board, to install the new CU. I reused the thing from the old CU to anchor the incoming armoured cable to the new CU; it attached bit like an old co-ax TV aerial termination.

Do you mean an SWA gland?

Have you ensured this galnd was properly earthed?

What size and type was the OCPD supplying the new SWA feeder?

The incoming tails were old colours: red for live, blue for neutral and plain yellow for earth.

They should have been sleeved to either the old standard or the new standard. It is not acceptable to have both.

All bend round to the left and then up; I sleeved the end of earth in yellow and green which takes up the first three sockets of the earth strip,

Why? Apart from it looking an absoloute abortion, there is no need to split it across three terminals.

The yellow and green on the right hand side is just a bonding cable that I've reused from an old installation.

Where do these terminate to?[/quote]

 

[RF Lighting]

As for my 50mm chases, I have the floor up so virtually the whole run is through floor voids. There's a bit in the stud wall where the CU is, which is just over 50mm including an inch of plasterboard on each side.

Plasterboard is not an inch thick.

If the plasterboard is on how are you going to prove to the inspector that none of your cables end up less than 50mm deep at any point?

Then there will be short vertical chases up to each socket. The plaster on my external walls is also over 40mm deep in most places - do the permitted chase proportions include plaster?

Yes, are you saying that you have chases 20mm deep into your brickwork before the plaster has gone on?

 

[mikeyd]

Well done you. You obviously are going about it in the proper way, asking advice etc.

My tuppence worth: There isn't anything I can see which it dangerous or stupid but it all looks a bit 'strange'. Just not the way an experienced electrician would do it.

Out of interest, what IT equipment do you have to justify not putting it through an RCD/RCBO? Bearing in mind if it was supplied through an RCD and for example your computer did have an earth fault, or got flooded by a burst pipe etc.

It's a standard 2.5sqm T&E ring - rated over 20A. That should allow me to have an oven up to about 4.5kW, no? There is nothing else on this ring.

As far as I remember, ring final circuits are only ever used and approved for sockets. Doubling up conductors to supply an oven may be allowed but it isn't a ring, and anyone testing it might wonder why you did it like that.

Keep going though.

Edit: must type faster regarding the oven 'ring'.

 

[rcd1976]

As for my 50mm chases, I have the floor up so virtually the whole run is through floor voids. There's a bit in the stud wall where the CU is, which is just over 50mm including an inch of plasterboard on each side.

Plasterboard is not an inch thick.

If the plasterboard is on how are you going to prove to the inspector that none of your cables end up less than 50mm deep at any point?

Then there will be short vertical chases up to each socket. The plaster on my external walls is also over 40mm deep in most places - do the permitted chase proportions include plaster?

Yes, are you saying that you have chases 20mm deep into your brickwork before the plaster has gone on?

Two layers of 12.5mm plasterboard are an inch thick. It is currently only on one side so inspector will be able to see location within stud wall.

The plaster is on most of the walls already, and has been extensively channelled already. The oven point comes up in a stud wall so there is only one channel into very deep plaster for the computer, about a foot long. Rest is in voids.

I don't know exactly what the OCPD of the communal distribution is, but it's not my property anyway; I haven't modified it in any way from the previous installation, which was signed off.

The SWA gland attaches to the CU box, which is definitely earthed. Is that not sufficient? What would I need as well?

The 25sqmm incoming earth simply would not fit in less than three of the board's earth terminals. Should I have used a termination before the board terminals?

The bonding is still attached to the water pipes as it was in the previous installation. I haven't modified this bit either.

As for the 20A oven ring, I could put a 32A MCB on it instead but thought it was better to come down to under the cable's maximum load.

 

[ABCwarrior]

I too think "good effort".... It is a DIY forum after all!!!

(Having spent 3 months living in in some dodgy places in the Ukraine some short few years ago you should see what passes as acceptable in these places!! )

 

[EFLImpudence]

It's a standard 2.5sqm T&E ring - rated over 20A. That should allow me to have an oven up to about 4.5kW, no? There is nothing else on this ring.

That's alright then, I just thought they looked smaller (than 2.5) and wondered why two on oven circuit.

In fact, larger than 4.5kW with diversity.

No it's not alright.

BS 7671 only recognises ring final circuits on a 30A or 32A OCPD

Accepted - you have instructed me on this before and I agree.


However, in this case with only one appliance on the circuit the MCB will not be overloaded (much less than a 32A on a ring) and so, as has already been said, it should be regarded as conductors in parallel (can we assume they run together) and not as a ring, as such.

As you go on to say -

The circuit you have is a none standard circuit. You will need to show all your design calculations to the inspector to prove it is compliant with BS 7671, not to mention it's a horrible way of supplying a single appliance.

A 4.5kW oven would be satisfactory on a 20A MCB with only one 2.5mm² so two will be more than electrically compliant.

I suppose it would be better (installation methods allowing) if one of the conductors were disconnected (at both ends).

 

[rcd1976]

A 4.5kW oven would be satisfactory on a 20A MCB with only one 2.5mm² so two will be more than electrically compliant.

I suppose it would be better (installation methods allowing) if one of the conductors were disconnected (at both ends).

Yes, I could still do that. Would it be better just to run a single 2.5sqmm cable for an electrical oven up to 20A/4.5kW? The run is about 10m nearly all through floor void.

Thanks again.

 

[EFLImpudence]

Would it be better just to run a single 2.5sqmm cable for an electrical oven up to 20A/4.5kW? The run is about 10m nearly all through floor void.

Yes, as long as it runs through NO conduit or thermal insulation.

Or, if it does, you could run some 6mm².

Normally oven (cooker) circuits are run in 6mm².
However, if all you want is 20A then not necessary.

 

[ban-all-sheds]

Well done you. You obviously are going about it in the proper way, asking advice etc.

No - he is designing circuits without knowing what he is doing, installing SWA without knowing how to do it properly, energising it all without testing and asking questions after the event.

 

[ban-all-sheds]

I too think "good effort".... It is a DIY forum after all!!!

And the reason that it's OK for DIYers to work to lower safety and knowledge levels than professionals is what, exactly?

 

[jobin]

I have concluded that 'ban all sheds' is either afflicted with the mother of all constipations or he is a paid promoter of the Electrical Workers Union. Of course, both may be operating concurrently.

 

[mfarrow]

BS 7671 only recognises ring final circuits on a 30A or 32A OCPD.

Under what regulation?

The regulations permit the installation of a 32A ring using cable rated at 20A for historical purposes.

The regulations do not preclude the installation of a 20A ring using cable rated at 20A, nor a 6A rated at 6A, etc.

 

[mikhailfaradayski]

BS 7671 only recognises ring final circuits on a 30A or 32A OCPD.

Under what regulation?

try looking at 433.1.103. I wonder what BS1363 devices the OP has used in his cooker circuit?
Also, just for information, have you looked at the notes in appendix 15. What does it say about cookers and similar devices with a rating over 2kW?

The regulations permit the installation of a 32A ring using cable rated at 20A for historical purposes.

What do you mean 'historical purposes'?

The regulations do not preclude the installation of a 20A ring using cable rated at 20A, nor a 6A rated at 6A, etc.

Maybe not, but why would anyone bother with such a circuit at the point of installation? What benefit would you get?

 

[ban-all-sheds]

try looking at 433.1.103.

Try looking at the rest of 433, and grasping the fact that 433.1.103 allows an exception for ring finals serving BS 1363 accessories etc from the general rule requiring Ib ≤ In ≤ Iz. With 2.5mm² conductors on a B20 no exception is required (installation method permitting).

I wonder what BS1363 devices the OP has used in his cooker circuit?

He doesn't need to.

Also, just for information, have you looked at the notes in appendix 15. What does it say about cookers and similar devices with a rating over 2kW?

It says it should be on a dedicated radial circuit, which it almost certainly is.

What do you mean 'historical purposes'?

Continuing to allow the traditional ring final, which was introduced for reasons of expediency but logically should not be permitted?

Maybe not, but why would anyone bother with such a circuit at the point of installation? What benefit would you get?

Resilience. Reduced voltage drop.

 

[ban-all-sheds]

I have concluded that 'ban all sheds' is either afflicted with the mother of all constipations or he is a paid promoter of the Electrical Workers Union. Of course, both may be operating concurrently.

You need to work on your concluding skills - you've either overlooked or stupidly dismissed the conclusion that neither is operating and that I simply do not tolerate incompetence nor believe that DIYers don't have to know about proper design and proper testing etc.