cu change and existing circuits

[damo16v]

hi,

i'm going to replace my cu and use this for part of my assessment to become registered with elecsa so i can certify my own work.

i have never done a cu change and have a few things i need clearing up before i attempt it.

current installation consists of lights, sockets, cooker , emersion (blank) and thats it!

i'm going to install a wylex dual rcd 10 way jobby, got to upgrade the tails, main earth and bonding


question 1: the current installation has the upstairs and downstairs lights on the same breaker now under the 17th ed the bathroom lights should be rcd protected do have to alter the installation to meet this, also should i seperate the upstairs and downstairs lights or is this just recommended for new builds?

question 2: the sockets are all on 1 breaker should i seperate the circuits and put them on different rcd's as the regs state?

question 3: i have a cable run for an emersion heater but there isn't one installed at the moment there is a blank over the fuse in the current board what should i do with this circuit when the new board is installed?

thanks in advance for any replies.

damian

 

[bugsy]

I would split the lighting, split first and ground floor ring have you carried out I/R test,
Lenny has posted a very useful thread ( sticky's ) regarding C.U. change , you will find it very informative

 

[damo16v]

hi,

thanks for the reply.

yes i have completed all tests on the current install when i was at college so IR is fine.

i have spoken to several sparks who say they would split the ring up/down but wouldn't bother with the lights thats why i am asking on here how far you need to go when replacing the cu, because i will be assessed on it i want to get it right.

ok thanks will have a look.

 

[bugsy]

Well if you only have one lighting circuit you cant split it across the two rcd's so if a fault occurs on the rcd side feeding the lighting circuit at 11pm you have no lights!
Health and safety issue

 

[Mr Mark Sparks]

you only have to do the best you can with what is there if there is 1 lighting circuit you dont have to split it up
likewise with the ring

 

[acat]

If your assessor feels that you are not really interested and will take short cuts where ever possible it will make your assessment a long and difficult one so do everything as per the regs and your pass is in the bag.


Good luck and let us know how you got on.


Chris

 

[oldtimer]

when lights are doubled up it is because someone needed a spare way in the past or that they share a neutral either way better to split them up. As for the immersion if it is wired then connect it up yes I know you dont use it but you may need it in the future.

 

[mattcos1972]

Have a look at this chap....

Basically you need to either do a periodic beforehand or a thorough pre change check over including R1+R2 and Insulation Resistance (cross connected @250v if necessary) on EVERY circuit.
All rings need to be complete (ie not broken), or reconnected as radials, and the property must be adequately bonded to current version of BS 7671 (ie main bonding to water and gas etc in 10mm). If it isnt then dont to the job, or get it up to scratch beforehand.

Best of luck.

Matt

 

[Johno]

every job is different, i dont mean to state the obvious but you cannot just separate up and down, lights and sockets with a cu change(most the time)

 

[WayneL]

I think I agree with you, johno, and Mr Mark Sparks.

How the hell do you seperate a single ring, feeding sockets both up and down, into two rings - without the place looking like a bomb had hit it afterwards.

Imagine the look on the customer's face when they came home - they asked for a CU change and now the house needs re-decorating lol

 

[mattcos1972]

I think the problem is that this is an assessment job, guys. Elecsa are gonna want the I's dotted and the T's crossed.
In the real world things may be a bit different (although probably shouldn't be), but rightly or wrongly, when a doing a Part P assessment if you are ever gonna adhere to the rules to the letter then this needs to be the time.

Best practice for a CU change is that if you cant guarantee that everything is up to scratch on reconnection then steer well clear and find an easier one to get assessed on.

I am presently doing a CU change for NICEIC inspection and it has required untold remedial work before the CU change can be done. Rings were broken, house not bonded, garage and several spurs in house wired in twin rubber cable with no earth.....you cant just bung all that in a 17th edition CU, say it was there when you got there and pass it off for 10 more years.

 

[mattcos1972]

Sorry guys.

I just wanna add that I don't mean that rings and other existing circuits have to be split in separate ones. They just need to be fully functional or not be re-energised (which you cant do as a general rule in a domestic situation ) Just leave a note in the comments section for that circuit if you consider it is too big, or covers too many floors, not enough sockets etc..... the list goes on forever.

 

[Johno]

you can pick which job you show the assessor, inc finished ones. so if i were you i would choose a nice one. but they are nice and helpful, if you are qualified, etc then you have absolutely nothing to worry about

 

[jase]

just change the CU,with existing circuits as long as they test out ok and put on the install cert recomendations for the work of spliting circuits it would be just as cheap to put in a 8 way board with main switch and the 4 rcbo's this would leave 4 spare ways for the future wiring and as every cicuit is rdc protected it complys with regs, the 17th allows for the fact that a lot of installations are wired to 16th and as long as they conform to the 16th i.e. EEBADS, it is fine to keep them like that as long as any new work conforms to 17th.

 

[Johno]

RCBOs all the way, yeeeeeeeeeee haaaaaaaaaaaa