How to modify a 16th into 17th Board

[brummydave]

I have a ponderance.... When encountering a split load board that complied with the 16th edition, how is it possible to make it 17th compliant?

Rather than replace an entire consumer unit, I've been contemplating modifications. One existing situation has a MK Sentry 12 way board (100A Main Isolator, 80A RCD) with the busbar cut to make it 5 unprotected ways and 7 RCD protected ways (2 of which are spare).

To RCD protect all ways, one option is to fit 5 RCBOs, but this costs way more than a new board.

I could fit another 80A RCD to protect the first ways, so making it a dual rcd board. However this has no high integrity circuits, or indeed capacity for extra circuits.

I could fit another small board for extra circuits.

Or can I remove the 100A DP isolator and so free up another two ways? There's already a 100DP isolator in the tails from meter to board, clearly labelled, and only an arms length from the existing consumer unit too.

I asked MK technical and they couldn't grasp the concept.

Am I missing something or would this be compliant?

Ideally I would end up with

2xRCBOs, 1 x 80A RCD protecting 6 ways and another 80A RCD protecting the final 6 ways.

All advice, and any reg references, most gratefully recieved!

 

[NozSpark]

Why do you want to do this?

 

[m4tty]

Someones gotta ask .... whats the Earthing Syetem ?? TT/TNCS/TNS ??

 

[Steve3948]

I agree why ? or is it you need to add circuits.

 

[m4tty]

Some customers not many do actually want a fully complaint install to latest regs. They must have too much money

 

[kme]

If you have two spare ways - it isn`t a problem; dependant on the exact DB in question - as you also need another Neutral bar!!!!!

Unless you want to keep spare ways - then it IS a problem. I`ve done this in the past.

 

[brummydave]

Thanks for your replies There's a few reasons why I'm looking at this.

One, because several circuits are to be modified and so will need RCD protection due to the buried cables.

Two, to add a circuit or two.

Three, to arrange the circuits better for safety. I.e. up lights/down sockets on one RCD and down lights/up sockets on another...

FYI, The earthing is TNC-S.

Thank you.

 

[hxsarge]

na nana na na na....stop rcbo time!... mc screwdriver that

 

[brummydave]

If you have two spare ways - it isn`t a problem; dependant on the exact DB in question - as you also need another Neutral bar!!!!!Unless you want to keep spare ways - then it IS a problem. I`ve done this in the past.

How've you done it please?

Did you need the third Neutral bar for the RCBO's?

Or leaving it RCBO free, did you remove the DP main switch?

Thanks for your help.

---------- Post Auto-Merged at 21:55 ---------- Previous post was made at 21:48 ----------

Some customers not many do actually want a fully complaint install to latest regs. They must have too much money

Surely whether customers want a compliant install or not is irrelevant when work is done, as it has to be compliant for notification? Or am working in the wrong way?

 

[NozSpark]

The installation doesn't have to be compliant,,,, only the work you do does

 

[steptoe]

you dont need 3 neutral bars, only 2, unless you want 2xRCDs and RCBOs as well.

but, TBH, if you want me to actually explain how its done put a post in the beginners section,

its very simple basic connections, there is NO rocket science or, (unfortunately), voodoo magik involved.

---------- Post Auto-Merged at 22:07 ---------- Previous post was made at 22:05 ----------

but, if you only want to make a 16th edition board compliant with the 17th edition then the simplest way is to put a '17th edition compliant' sticker on it.

 

[brummydave]

na nana na na na....stop rcbo time!... mc screwdriver that

eh?

---------- Post Auto-Merged at 22:45 ---------- Previous post was made at 22:43 ----------

you dont need 3 neutral bars, only 2, unless you want 2xRCDs and RCBOs as well.but, TBH, if you want me to actually explain how its done put a post in the beginners section,

its very simple basic connections, there is NO rocket science or, (unfortunately), voodoo magik involved.

---------- Post Auto-Merged at 22:07 ---------- Previous post was made at 22:05 ----------

but, if you only want to make a 16th edition board compliant with the 17th edition then the simplest way is to put a '17th edition compliant' sticker on it.

Not sure about the sticker bit, lol!, but thanks for the reply. I do understand the connections stuff, I was mostly just after options for the board.

Oh, and whether or not removed a DP isolator from a board is ok or not.

 

[steptoe]

I wouldnt remove the main switch,

although I suppose technically you could, you still have your main isolator externally,

but in a domestic situation would the householder think like that?

 

[sparkytim]

If you do not want to go with RCBOs as replacement for non-Rcd protected MCBs then replacement of the whole Board with a duel RCD Unit is most likely the better more economical option given the discounted cost of them at present.

 

[NozSpark]

I've used an external isolator before going into a sideways mounted CU full of RCBOs (& 1 x 25mm din rail terminal for the neutral)

 

[springcrocus]

One thing you might like to consider is the PFC. If this exceeds 6kA (unlikely in a domestic situation, I know) then your board may not be compliant. The individual components are all likely to be rated at 6kA but a maufacturers board generally has a 16.5kA rating due to some jiggery-pokery with type testing and the rating of the upstream fuse. Once you deviate from the manufacturers intended design, you're back to working with the rating of the worst-case item in your construction because the manufacturer will maintain that the equipment has been modified and the type-testing approval no longer applies.

 

[kme]

What was done in the example I gave:

Two spare ways were "done away with", to make 2 module space for another RCD next to the main switch - Split load wiring kit, three steps to left whilst incanting the magic words (Albert - we`re allowed to say that they exist - but you mustn`t say what they are!!!!!), and it`ll work fine

I wouldn`t take a main switch out of a DB either - it just doesn`t seem right.

 

[sparkytim]

One thing you might like to consider is the PFC. If this exceeds 6kA (unlikely in a domestic situation, I know) then your board may not be compliant. The individual components are all likely to be rated at 6kA but a maufacturers board generally has a 16.5kA rating due to some jiggery-pokery with type testing and the rating of the upstream fuse. Once you deviate from the manufacturers intended design, you're back to working with the rating of the worst-case item in your construction because the manufacturer will maintain that the equipment has been modified and the type-testing approval no longer applies.

Back up protection by a 1361 type service fuse will provide 16 k A PFC rating.

 

[springcrocus]

Back up protection by a 1361 type service fuse will provide 16 k A PFC rating.

That's the point I am trying to make. A consumer unit is only rated at 16.5kA because of type-testing. Once you modify it beyond manufacturers recommendations (e.g only use our MCB's etc) then that rating no longer applies and the rating of the lowest suseptible component applies, which is usually 6kA.

If your local tranny is only fifty yards away, you could be looking at a Ze of 0.03 or less which would give a PFC of 7.67kA or more. If the next component after the service fuse (likely the isolator switch) is only rated at 6kA then it could fail under fault conditions.

I have reconstructed many a CU myself, I was just pointing out the risk if you have a high PFC. If an isolator switch burns up because of high fault current, and you have installed the CU as recommended, then the manufacturer has a problem. If YOU modified the board then YOU have a problem.

 

[brummydave]

That's the point I am trying to make. A consumer unit is only rated at 16.5kA because of type-testing. Once you modify it beyond manufacturers recommendations (e.g only use our MCB's etc) then that rating no longer applies and the rating of the lowest suseptible component applies, which is usually 6kA.If your local tranny is only fifty yards away, you could be looking at a Ze of 0.03 or less which would give a PFC of 7.67kA or more. If the next component after the service fuse (likely the isolator switch) is only rated at 6kA then it could fail under fault conditions.

I have reconstructed many a CU myself, I was just pointing out the risk if you have a high PFC. If an isolator switch burns up because of high fault current, and you have installed the CU as recommended, then the manufacturer has a problem. If YOU modified the board then YOU have a problem.

Good points, well made. Thinking cap truly on. Thanks