Rewiring upstairs lighting circuit

[TomSparkman]

Hi everyone,
I am to rewire the upstairs lighting circuit as the old switches, pendants and cables are outdated.
The existing consumer unit is old but still has mcb's rather than rewirable fuses, but NO RCD protection.

The first question is, does the new replacement circuit HAVE to be RCD protected? I'm pretty sure it does, as my new cables will be chased in to the walls but NOT 50mm deep (obviously in prescribed zones)

Second question, rather than put a whole new CU in as this may introduce problems with the other circuits, would it be good practise to mount a small garage CU next to the existing CU? This garage CU would have a 30Ma RCD and space for two mcb's.

Third question is, what would be a suitable way of feeding the garage CU? And a suitable means of isolation?
My thoughts were to double up the tails in to the load side of the main isolator with the existing CU and to terminate the earth in to the earth bar in the existing CU.
Another option which is possible would be to split the existing tails between the 100 fuse and the existing CU and surface clip to the garage CU roughly a meter away.The flaw in this is that I would have to remove the main fuse, which is obviously bad practise.

Thank you in advance for any advice

 

[DanDobson]

If the 13A fuse is in the RCD FCU will there not be a diversity issue as the new RCD FCU will be fed by the current 6A upstairs MCB?

May have mis-read above so ignore me if I have

Dan

 

[telectrix]

If the 13A fuse is in the RCD FCU will there not be a diversity issue as the new RCD FCU will be fed by the current 6A upstairs MCB?

May have mis-read above so ignore me if I have

Dan

EVEN WITH A 5a FUSE, YOU WILL GET DISCRIMINATION PROBLEMS AS THE 6a mcb WILL MOST LIKELY GO FIRST.

 

[DanDobson]

EVEN WITH A 5a FUSE, YOU WILL GET DISCRIMINATION PROBLEMS AS THE 6a mcb WILL MOST LIKELY GO FIRST.

Yeah good point Telectrix, how should the OP get round that issue then?

 

[telectrix]

i'd not bother. stick a 13A fuse in as the cable is adequately protected by the 6A MCB

 

[J.C.E]

And if your planning of re wiring the whole circuit anyway (new circuit from db) bonding will need to be in place anyways and to issue a eic regardless of upgraded the db or not.￾

 

[TomSparkman]

Just explain to the customer the different options and the advantages/disadvantage of doing it that way- and then its up to them- you can only give them your opinion

Yes I'll do that, after all they're the ones paying for it!

 

[TomSparkman]

And if your planning of re wiring the whole circuit anyway (new circuit from db) bonding will need to be in place anyways and to issue a eic regardless of upgraded the db or not.￾

Wouldn't it be a minor works certificate it needed?

 

[Leesparkykent]

Wouldn't it be a minor works certificate it needed?

Not if it's a new circuit.

 

[Octopus]

Not if it's a new circuit.

And its notifiable under Part P too!

 

[TomSparkman]

Not if it's a new circuit.

So would that mean a full inspection and rest has to be done on the whole installation? Rather than just the new circuit

 

[Octopus]

So would that mean a full inspection and rest has to be done on the whole installation? Rather than just the new circuit

No.

You need to complete an EIC and the description of the works would be along the lines of "rewire of circuit # x upstairs lighting circuit"

 

[Leesparkykent]

So would that mean a full inspection and rest has to be done on the whole installation? Rather than just the new circuit

No you would have to complete an EIC for the new circuit and ensure the earthing and bonding arrangements are adequate.

 

[TomSparkman]

I understand now, thanks for your help everyone. Some good and much needed advice has been given!

 

[Octopus]

I understand now, thanks for your help everyone. Some good and much needed advice has been given!

Your schemes tech support can help too!

 

[Marvo]

If the 13A fuse is in the RCD FCU will there not be a diversity issue as the new RCD FCU will be fed by the current 6A upstairs MCB?

May have mis-read above so ignore me if I have

Dan

I assume you mean a discrimination issue?