CU Change

[walec]

As part of my part P assessment I am changing a CU in a 1960`s Bungalow. Its a PME supply.
we have:
100A main switch
5A lights
5A lights
30A ring
30A ring
5A lights
15A radial
30A cooker
currently on rewireable fuse board.
I can not make my mind up between single RCD split board or dual RCD split board with 100A main switch.
The Bungalow has been considerably extended over the years, last work done in the late 80`s.
All old colour wiring.

The reason for Dual RCD thinking is the wiring is questionable in places (wiring is generally unprotected between Cavity wall) there are junction boxes all over the place and I am not sure if this wiil be picked up on my Elecsa Assessment.

But not sure if that is the right call.
Brought the tails and bonding up to date.
Any advice is welcome.

 

[leonard290]

thorough insulation test will guide you.ie; neutral earth faults they will trip rcd's as mcbs wont,.then ring continuity tests.r1+r2 after that.follow the on site guide on pir inspection.i reckon a complete rewire will definitely be the answer.also all them jbs suggests problems with zs test. do them at every socket.also a thorough visual on 50%.visual always comes FIRST.

 

[sparks1234]

How are you going to comply with 17th if you install a single RCD board?

 

[walec]

I plan to do some testing tomorrow, I think you are right about the rewire but not what the customer wants at this time. I will see what results I get. Thanks for the advice.

To comply with 17th I was going to use a splt load 100A main switch and split load protected RCD CU

 

[sparks1234]

from your original post it seems as though you are only using one RCD though

 

[chocolate]

Hi. Is there enough space to fit a dual RCD board. You have 7 circuits, so you could split them 4 and 3 with each RCD module. Youo'll need a 10 or 12-way dual board. If space is a problem, go for RCBOs. More expense but eliminates nuisance tripping of RCDs to unaffected circuits.

Whatever CCU, make sure it has a 100A main switch to act as an isolator.

When you change that CCU, you must always think to yourself ( whether or not ELECSA are assessing ) that the whole installation is as good as it should be !!!! If you feel or discover stuff isn't right, you must sort it before you do the certificate. Only change the CCU if you are prepared to verify that all circuits connected to that CCU are sound and meet 17th requirements.

If there are loads of JBs, have you checked them for secure connections and correct identification, etc. Elecsa could ask you to open one up in front of them !!!

 

[flip73]

if your doing a cu change you have to test every circuit you put back in your new cu, that will then also tell you if it needs any work doing, i'd definitely go for either twin rcd board or maybe single split plus rcbo's depends on budget

 

[walec]

Thanks Guys this confirms my thoughts.
Space is not a problem so I will go for a spilt RCD Board with 100A main switch.
With regard to the Junction Boxes, I am not too happy with them, I will check and test each circuit before I put it into the new CU, if I am not happy then I will propose a rewire of that circuit.
I guess this could end up as a complete rewire but if that is what is required so be it.
Thanks again

 

[tuckermot]

Hi walec
i would visual check the whole installation before i go any where near the ccu with my test gear !! the reason being you can find many faults / non compliances this way and dont forget what you can see so can the inspector !!! only when i have corrected these would i go ahead and test .as you are changing the ccu you really should make sure every thing is ok even though you did not install it before ccu change

good luck buddy!!

 

[walec]

Thanks tuckermot, good advice, I was planning too, the more I look at this the more i think it will be a full challenge, I think I may have picked a steep learning curve on this one, but at least I can put it down to good experience as there are sure to be problems along the way.

 

[tuckermot]

yuor welcom walec

 

[TPES]

So you say that before changing a CU that every other circuit in the installation must comply with the 17th regs, Where do you draw the line with that, You could end up on most CU changes with a huge list for the customer of work that doesnt comply to 17th.

Example, what would you do if you are asked to change CU but find on upstairs lighting that in the bathroom there have been Non IP rated mains downlights fitted above bath/shower, and have been there for many years. but customer doesnt want to start paying out for many altertions around the home

 

[Had8Lives]

What out for borrowed neutrals on two way switching. It will trip both RCDs at once.

 

[wigan]

Try this link http://www.niceic.org.uk/inc/file-get.asp?FILE=NICEIC-BPG6.pdf&RURL=/en/contractor/section.asp||13

Think the only upgrade you may have to do is with regard to earthing and bonding 131.8

You don't have to upgrade all circuits to current regs