Riser emrgency lighting

[silentboarder69]

I was on a site today in central London. The building had boilers in the basement, and then two risers, each with a stairwell for access over eight floors.

I was called as the lights don't work in the stairs. After some investigation and getting pretty sweaty, I found the wires had been cut and some of the conduit removed. At the bottom of riser one, where the access is from the boiler room, a new light had been fitted.

The new light was an emergency light, and had a cpc run to it. In the old lighting system, there was no CPC, the light fittings were very old, with ceramic connectors.

I ran a 500v IR test, all the old cable was fine. It looks like the lights had been run as a ring, which (of what was left) was still OK.

My first concern was, why has this been excluded? Is it because it had no CPC? It looks like the lights are earthed to the conduit. Is this acceptable? Or was it excluded due to lack of CPC and whoever excluded it couldn't be bothered (or wasn't contracted to) to replace the old cable and light fittings.

I've advised that the old light fittings should be replaced with double insulated fittings, and new wiring to include a CPC, before being integrated into the new light at the bottom. Is this correct advice, or unnecessary work?

Thanks in advance!

 

[Des 56]

Read 543.2.2 (vi)

 

[Engineer54]

I think i've heard it all now!!! You actually advised that these light fittings be replaced with D/insulated fittings on a metallic conduit system?? .....Geezus Christ!!!

Since when does a metallic conduit system require a CPC?? Conduit has been used as the CPC since the first length of the stuff was first installed!!!

 

[silentboarder69]

Well, the riser houses the two chimneys for the boilers, and since all the other lights in the building had been replaced with double insulated fittings, I'm assuming there was a reason for this (sprinkler system?)?

And also, the previous work carried out have installed a CPC. I thought this odd, as usually the metal conduit is used.

So, it struck me as odd, and I wanted to investigate further (which is the point of forums such as this I believe) but thanks for your useless reply. Perhaps you should start a forum for useless replies?

Also, if you carry out an install for the NHS, the often specify a separate CPC. I hope that answered your question succinctly.

 

[Engineer54]

Don't think you can start blaming me for your own failings, that ain't gonna wash!!

You didn't come to investigate further, as you have already advised the customer/client that the present fittings should be replaced with class11 fittings. So you may have been looking for confirmation rather than investigation.

The presence of sprinkler systems would if anything, only call for a suitable IP rating, not Class11 fittings!! The only time a separate CPC is required in a metallic conduit system, is if there is proven deterioration of it's continuity. So what tests have you made in this respect, instead of wondering why others had pulled in a separate CPC conductor to a new fitting???

As far as NHS installs, ...every hospital Engineer can specify as he pleases, many are not Electrical Engineers but Mechanically biased. Why would anyone (unless who didn't know any better) supplement at extra costs to the project, an earthing system that will vastly exceed any CPC requirements in overall CSA?? It certainly isn't called for in a hospital related installations that is metallic conduit/trunking based!! I've worked on hospital projects for a good many years now, and currently so, too.

I'm not accustomed to making useless statements to you or anyone else!! Shocked statements are another thing altogether!!!

 

[silentboarder69]

I will apologise for saying I had advised to replace, I haven't filed my report yet. Hence investigating why someone might put classII fittings in before going further.

Re the hospitals Health Technical Memorandum
06-01: Electrical services supply and distribution:

"Circuit protective conductors
13.32 All parts of the LV distribution including final
circuits will have a separate circuit protective
conductor (CPC)...
13.33 Where circuit cables or conductors have an
integral metallic sheath, the sheath will not be used
as the sole earth return path. Designers should
consider the use of multicore cables with an earth
conductor, or where this is not possible, installing
a separate CPC."

 

[Engineer54]

I will apologise for saying I had advised to replace, I haven't filed my report yet. Hence investigating why someone might put classII fittings in before going further.

Re the hospitals Health Technical Memorandum
06-01: Electrical services supply and distribution:

"Circuit protective conductors
13.32 All parts of the LV distribution including final
circuits will have a separate circuit protective
conductor (CPC)...
13.33 Where circuit cables or conductors have an
integral metallic sheath, the sheath will not be used
as the sole earth return path. Designers should
consider the use of multicore cables with an earth
conductor, or where this is not possible, installing
a separate CPC."

If there is no deterioration in the continuity of the conduit system being used, then i can only say, pure ignorance is the reason a separate CPC has been pulled into the conduit...

Think you'll find that 13.33 is referring to armoured sheathed multi-core cables, not conduit or even MICC cables.... 13.32 Metallic conduit IS the separate CPC. Nothing in those two specification clauses you have posted implies metallic conduit requires a separate ''copper'' CPC conductor, because it doesn't and never has.