CPC common to 2 circuits...

[timhoward]

When I checked out this job I had a false sense of security from a recent competent looking EICR and two new CU's that looked to be fitted to a high standard. Most of the property does have a CPC on the lighting circuit, it's just this one room with a flat roof above that doesn't. This is where I need to extend from for some new downlights.
I completely messed up here, I checked the fitting weeks ago and went away thinking all is fine, there's a switch wire with no CPC that I can replace.
It turns out the neutrals were being switched and I managed to misread which cable was missing the CPC, it's the feed. (When I return I'll see if the CPC in the switch wire is connected to MET or just there for show. I think I can guess the answer.)
So completely my fault but reality is that 1st fix is in, boarded over and skimmed...aaargh!

I believe the regs permit running a 4mm single from (in this case) the cooker circuit to the new light switch which would mean the extended feed has a CPC. Label at CU, note on certificate etc? Far from ideal, but acceptable?

Only other option I can think of is putting the lighting on an FCU on the RFC and avoid touching this circuit at all.

 

[timhoward]

I believe the regs permit running a 4mm single from (in this case) the cooker circuit to the new light switch which would mean the extended feed has a CPC. Label at CU, note on certificate etc? Far from ideal, but acceptable?

Looks like no-one wants to be seen endorsing this approach!
Anyway I've since realised that the lack of CPC on lighting stuffs up my smoke alarm plans too so I'm trying to convince the customer that getting the lighting sorted once and for all is in their best interests.

 

[Electro-tech]

Looks like you are on your own on this one, everyone is at the nearest watering hole or something like that.

 

[timhoward]

Looks like you are on your own on this one, everyone is at the nearest watering hole or something like that.

Can't blame them, it's ridiculously hot to be working attempting to think straight and work.

 

[brianmoooore]

I believe the regs permit running a 4mm single from (in this case) the cooker circuit to the new light switch which would mean the extended feed has a CPC. Label at CU, note on certificate etc? Far from ideal, but acceptable?

Correct. Acceptable, but likely to get mutterings from the person doing the next EICR.
Was a fairly common thing to do in the 70s and 80s, when modify or adding to pre CPC lighting circuits.

 

[timhoward]

Correct. Acceptable, but likely to get mutterings from the person doing the next EICR.
Was a fairly common thing to do in the 70s and 80s, when modify or adding to pre CPC lighting circuits.

Thanks Brian.

At the moment the plan is unfortunately back to doing exactly that for the kitchen downlights as I'm failing to find a cable route.
[It shouldn't affect my thinking but house happens to be TT with a not very impressive 150 ohms Ze and that's after 10 minutes with a hose! I'll be seeking to improve that before I go. The CPC will do hardly anything anyway right now!]

I think it actually best not to use the cooker circuit to supply a CPC as it seems that would need a 10 sq mm cpc to comply with corresponding with the largest line conductor .....
There's a convenient double socket too, which would be perfect for a label as it's behind a fridge freezer.

The good news is that it's been agreed to install a new cable upstairs, at this point just for smoke alarm but once kitchen finished (and weather more appropriate to linger in a loft!) the upstairs room without a CPC will be rewired.

So I think there's a compliant way out of this mess even if it isn't great.