Question regarding converting a 16th edition board to a 17th

[Bonce]

Hello,

Firstly I realise from various posts that the terminology above isn't always liked so apologies but think its the best way of explaining what I want to know.

I have a question regarding a board I bought some time ago which I want to have used to replace my old CU with. I have no intention of doing the work myself and know that I must get a person from the 'competent person scheme' to do the work, who will then test and notify the LABC, but I have spoken to a local sparky over the phone who has told me that I will have to get rid of the CU I bought and buy a new 17th edition CU.

I have used this site before in the past and I know I am no expert but from various posts I don't think this is entirely true so if anyone could let me know for sure then I would be very grateful.

I refer to the post entitled 'First ever CU and 17th edition to boot' hopefully this link works:

//www.diynot.com/forums/viewtopic.php?t=142216&start=0&postdays=0&postorder=asc&highlight=

In here there is a pictue of a board entered by Click-Sure, the second set of photos, (you cant miss it, its the extremely neat board). Now I think this is essentially the same CU I have. The one I already have bought is a Wylex split board with 12 MCB's and 1 RCD. Same as in the photo except where Clicks has an RCD to the left of the main switch mine doesnt and simply has 6 MCB's, which under 16th edition would not have been under RCD protection. Mine then has 6 MCB's under the next RCD.

Now I think the board can be altered and I think that if I bought another RCD - that it could be made to conform to 17th edition (with relevant care to spreading the lighting circuits between the two RCD's etc)

I am just confused about the busbar as unfortunately Click has left the guard in place in the photo. Obviously at the moment my busbar is split with the first prong of one piece coming from the live of the RCD and going into the 6 MCB's to the left under the RCD protection. The second piece has the first prong into the live of the main switch and then has the other 6 prongs in the 6MCB's (which under 16th would not have been under RCD protection.

Now my thinking is that the busbar that goes to the live switch should be removed and I should replace 2 MCB's with a new RCD (as looking at the one already in the board they take up 2 ways) and that the busbar should be altered to have the first prong going into the live of the new RCD and the other prongs to the 4 MCB's (I'd essentially lose two ways and be shortening the busbar? losing 2 ways is ok for the number of circuits I have). I then think I wouldnt have a bus bar at all into the main switch but obviously would need to double up on the live cable whcih currently runs to the existing RCB to run into the new RCB and likewise the same sort of arrangement with the neutrals.

I may be completely wrong on all this and the local spark may be completely right (in which case I'm sorry I doubted him) but I'd really like to know and understand this. I mean if I was being pedantic couldnt I replcae all the MCB's withe RCBO's to make it conform (I know that this would be expensive however and dont want to do this).

So if anyone could let me know whetehr my thinking is correct that would be great and if they have any handy pics or links where this has been done all the better. If this is the case needless to say I will contact a different electrician.

Thanks and sorry its a long post!

 

[Spark123]

You can use RCBOs instead of MCBs in the ways on the non protected side - probably the best option if you are intent on using this board tbh.

The cables from the main switch would need to travel to the tops of the RCDs, two cables terminating in the main switch. The bus bars connect the bottom of the RCD to the MCBs. The neutrals also need to be fed to one side of each RCD and up to their individual neutral rail.

 

[BS3036]

I think the biggest problem is splitting the neutral bar into 3 sections instead of two. It usually means you are short of one plastic piece.

 

[hairyben]

I think the biggest problem is splitting the neutral bar into 3 sections instead of two. It usually means you are short of one plastic piece.

If he's dual-RCD'in the board with no 3rd high integrity ways then he could feed both RCD neutral supplies straight from the main isolater.

however I'm with spark 123 on this, simpler just to wap RCBO's in, wylex are pretty cheap now, and their insulated boards should have enough height for this not to be a problem, unlike some of their metal range.

Either way it's possible, no absolute need for a new enclosure, although that could be desirable if there's a likleyhood of more circuits being wanted further down the line.

 

[Bonce]

With regards to having to split the busbar into 3 wouldn't it just simply need to be shortened and just have 2 pieces. One as present and then one from the new RCD to the MCB's not under protection. the main switch otherwise would just have one prong of busbar as it wouldnt be connecting to any MCB's.

So am I right in thinking that it would be the new connection (in wire) to the top of the new RCD for the live that would replace the need for this?

And many thanks for the replies it is very much appreciated, i want to try and avoid buying RCBO's to replace the 6 unprotected MCB's if possible as i believe this would probably be 6 times the cost of one RCD (from Screwfix).

 

[Spark123]

You wouldn't have any bus bar in the Main Switch at all unless you were having high integrity ways. The connections between the main switch and the RCDs are done using insulated cables.
RCBOs for £23.75 + VAT:
http://www.tlc-direct.co.uk/Main_Index/Consumer_Units_Index/Wylex_Ns_2/index.html

 

[hairyben]

With regards to having to split the busbar into 3 wouldn't it just simply need to be shortened and just have 2 pieces. One as present and then one from the new RCD to the MCB's not under protection. the main switch otherwise would just have one prong of busbar as it wouldnt be connecting to any MCB's.

So am I right in thinking that it would be the new connection (in wire) to the top of the new RCD for the live that would replace the need for this?

And many thanks for the replies it is very much appreciated, i want to try and avoid buying RCBO's to replace the 6 unprotected MCB's if possible as i believe this would probably be 6 times the cost of one RCD (from Screwfix).

Like spark123 says you'll run 2x flexi tails from bottom of the mainswitch to the top of the RCD's, then busbar from RCD L to MCB's

When comparing RCBO prices, it's only fair to compare 4xRCBO vs. 1x RCD, using 4 circuits as you would with the RCD... the difference being you have the option to keep the circuits at 6 if you wish.

yes, it's more expensive but

a) it's better and
b) with dual RCD you'll need to juggle (at least) lighting circuits across the RCD's, bringing at least 1 circuit back onto the new RCD, which is again more work and more testing, as is the time spent reconfiguring the board to dual RCD, and if you've got a spark working on an hourly rate...

.. it might not add up to such a great deal of difference.

 

[Bonce]

many thanks Sparks123

 

[Bonce]

take the point hairyben many thanks and yes 4 mcb;s as thee rcd would replace 2 - thanks again

 

[hairyben]

take the point hairyben many thanks and yes 4 mcb;s as thee rcd would replace 2 - thanks again

no problemo, the other thing to consider when "combining" circuits is, depending on circuit type and loading, it might not be so simple...

6 circuits, maybe a cooker, immersion and 4 lighting. Cooker and immersion must remain independant, so you're combining 4 lighting circuits into 2.

how many lights are on each circuit? Dedicated kitchen lighting circuit with 20 downlights plus pelmit lights etc? Don't wanna stick too much more on that... upgrade to 10A MCB's I hear y'say.. got any 1.0mm in insulation? Got any dimmers? don't wanna do that then...

So much to consider.. RCBO's could be a much simpler solution.

 

[Click-Sure]

Its nice to be noticed.

Just popped down to the garage (its my own CU) and taken a pic without the busbar cover.

Untitled

• Click-Sure
• 9 Nov 2008
• 1

 

[hairyben]

Its nice to be noticed.

Just popped down to the garage (its my own CU) and taken a pic without the busbar cover.

Untitled

• Click-Sure
• 9 Nov 2008
• 1

I'd have had shorter loops on the lives and done a neater job on the earths.

Plus you have the busbar cover off without switching off the mainswitch.

And your mainswitch is wonky.

Terrible, minus 10 points.

 

[Click-Sure]

Valid point concerning the earths.

I was wearing 500v gauntlets at the time.

If Wylex cant make a consumer unit without a straight main switch, well, thats their look-out!

 

[kai]

That Wylex looks very similar to my own one - except that the main switch on my one is dead straight!.

 

[Bonce]

Excellent Click-Sure thanks for that it is very much appreciated, and thanks again to all the other guys.