Light circuits in Consumer Unit

[Gavin John Hyde]

i don't have much domestic experience as i have worked largely in shops and pubs during refurbs.

I have a potential job lined up i want to use for the NICEIC assessment.

The customer wants a new consumer unit. The current one also has holes in the side from old cables and is barely hanging onto the cupboard wall. having looked at the set up all the lights (both floors ) are on one circuit..

With a little bit of investigation i found the reason for this is a shared neutral on the 2 way landing lights. when the current CU was put in the person who did it took both lighting circuits and put them on the one breaker. Most likely to stop the inevitable tripping the shared neutral would cause on a newish board.

The problem i have is the old lady whose house this is in, has recently had it decorated and is immaculate.. there is no way she will let me correct any problem cable runs in walls. there is no way to pull cables as they are plastered in with no conduit or trunking. likewise the attic area is all boarded out and is a room for the grand kids to play in.

I was always led to believe that with a split load board you should ideally put upstairs and downstairs lights on separate sides of board. so that if one trips the other floor still has lighting.

Is there a specific reg that says both light circuits can not be on the same circuit, i can not find one that clearly prohibits it, but neither can i find one that expressly permits it.

Any thoughts or ideas on how to handle this?

How common is this in UK homes?

When installing the new CU can i put both light circuits on the one breaker covered by one RCD? Or am i obliged to sort out the issue with shared neutrals so i can separate them out.

Any advice would be much appreciated.

 

[Midwest]

Reg 314.1, Division of installation. If you can't get a new feed in, what can you do. I've seen quite a few, including property with only one RFC.

Edit; If it's bought to the attention of the property owner, and they decline any rectification, a note can be made on the EIC. What does the NIC technical suggest?

 

[Wilko]

With that issue you are stuck with one light circuit, imho. Perhaps you could rcbo that circuit in the new cu to help increase its availability? As @Midwest suggests, note the issue on your cert and be ready for discussion with Assessor. It could be an opportunity to show you've been thorough

 

[Octopus]

No problem having all lights on 1 MCB/RCBO ... as long as the new CU has RCBO's

Or you could ignore guidance and best practice and do this:



3 storey house....

 

[Rpa07]

No problem having all lights on 1 MCB/RCBO ... as long as the new CU has RCBO's

Or you could ignore guidance and best practice and do this:

View attachment 36722

3 storey house....

In 4 x 10mm T+E in case of future proofing!

 

[Gavin John Hyde]

Having thought about this my thinking is that whilst not ideal due to the whole inconvenience factor if the lights go out (314.1.(i). it is unavoidable if the customer will not let me route new cables to fully separate the upstairs and downstairs light circuits. so long as they are aware of this and its documented on the paperwork what more can i do ?

given the cables are almost certanly less than 50mm in the wall there is the need for rcd protection as there is no protection from mechanical damage... so will a RCBO suffice?

my plan is to use a rcbo for the light circuits and then have 2 rcds for the remaining circuits. this way the shared neutral would not trip both rcds if the circuits were separate and nay issue would cause minimum disruption as it is on a rcbo so separate from other rcd protected circuits.
any thoughts?
what will the dreaded jobsworth from niceic say on the inspection/assessment as in my current job i never deal with them. I couldn't actually tell you what they think of my previous work as somebody else deals with the bureaucracy.

strictly speaking a shared neutral is in breach of 413.3.3 as it is really a borrowed live and not a neutral. and 413.3.3 says a live should not be connected at any point to another circuit. however by sharing the rcbo does the 2 light circuits then become 1... ??
this is surely no different to running a spur straight out the mcb rather than further along a circuit...

i have attached pictures of the CU as it is now, it is wobbly on the wall, barely attached with holes in the sides and you can put your finger in a empty way on the leftmost side... the 2nd is my proposed layout.

 

[Andy78]

If the householder will not agree to alterations then a note on the cert will suffice to make a record of the fact they were made aware of the situation.

Will an RCBO suffice in place of an RCD ? As long as it fulfils the requirements of the regs for additional protection for buried cables then yes.

No idea what the NICEIC will say, but I would say that you have demonstrated diligence towards the situation.

Yes if you incorporate two previous circuits into the same over current protective device they become one circuit by definition. This can be checked in the definitions section of BS7671.

Apart from being wobbly and lacking blanks, why does that CU need upgrading ?

 

[Flanders]

Your setup is the way I would do it , but just woundering why you are changing a consumer unit that looks to me that it could be easily repaired by blanking of the holes

 

[Octopus]

If you combine the up and down lights onto one ocpd then you have a single circuit.

Is the cu high integrity?

 

[Gavin John Hyde]

The consumer unit has several holes where circuits have been amended or moved over the years- i suspect it wasn't new when it was fitted but cant be sure as a friend of her late husband installed it.
There used to be cables and mcbs running to the garage that was replaced with a conservatory a several years back. These have been removed leaving holes and empty spaces in the CU.
I am not sure why but there is a crack along the bottom, it is in a coat cupboard and i think its more to stop the grandkids poking things into it, as it is about 4 ft off the ground level and above it is a row of coat hooks.
I did wonder about looking for a replacement outer body but it is a lot of effort and she wants a nice new metal CU like her friends have, its a bit like keeping up with the jones's ..

The CU i have in mind is High Integrity. I will likely use a decent Hager setup as i can get all the bits via my day job at cost price and for the same as most of the other decent quality makes from the usual suppliers.

 

[westward10]

Me I would personally want to split the lighting circuits which would involve some rewiring because I don't deem it a single circuit but it seems that is not possible. This sounds a straight forward task but the lady saying she wants a nice new metal CU like her friends doesn't sound true.

 

[Gavin John Hyde]

Me I would personally want to split the lighting circuits which would involve some rewiring because I don't deem it a single circuit but it seems that is not possible. This sounds a straight forward task but the lady saying she wants a nice new metal CU like her friends doesn't sound true.

Like yourself I would prefer to split the light circuits myself but chasing out the walls to get at the wires is a non starter as she recently had everything decorated.
She didn't actually say she wanted a new metal unit (my words!) but given all the new ones are AM3 metal jobs it goes without saying she simply stated she wants a new one and then told me all about her friends new extension and how they had the house rewired. eitherway its work for myself.

 

[richy3333]

That being the case maybe you should put something in writing to her to cover yourself against future criticism and potential perceived sharp tactics? Something to the effect that you have advised her the holes could be repaired/patched but she has asked you to supply and fit a new CU?

 

[Prat P]

Having thought about this my thinking is that whilst not ideal due to the whole inconvenience factor if the lights go out (314.1.(i). it is unavoidable if the customer will not let me route new cables to fully separate the upstairs and downstairs light circuits. so long as they are aware of this and its documented on the paperwork what more can i do ?

given the cables are almost certanly less than 50mm in the wall there is the need for rcd protection as there is no protection from mechanical damage... so will a RCBO suffice?

my plan is to use a rcbo for the light circuits and then have 2 rcds for the remaining circuits. this way the shared neutral would not trip both rcds if the circuits were separate and nay issue would cause minimum disruption as it is on a rcbo so separate from other rcd protected circuits.
any thoughts?
what will the dreaded jobsworth from niceic say on the inspection/assessment as in my current job i never deal with them. I couldn't actually tell you what they think of my previous work as somebody else deals with the bureaucracy.

strictly speaking a shared neutral is in breach of 413.3.3 as it is really a borrowed live and not a neutral. and 413.3.3 says a live should not be connected at any point to another circuit. however by sharing the rcbo does the 2 light circuits then become 1... ??
this is surely no different to running a spur straight out the mcb rather than further along a circuit...

i have attached pictures of the CU as it is now, it is wobbly on the wall, barely attached with holes in the sides and you can put your finger in a empty way on the leftmost side... the 2nd is my proposed layout.

View attachment 36729

View attachment 36730

You have advised her of the potential issues which are mainly an inconvenience as opposed to danger,if she has no lights in the house because a bulb blows it will be partially her fault and partially the fault of who designed the circuit. Note on the cert that your recommendation is to seperate the circuits but client has declined the advice