RCD Tripping when Lights turned on.

[ITS]

Just changed a CU - all ok apart from SOME lights trip the RCD when switched on - SOME lights work fine. Any ideas?

 

[Badger]

have you got a shared neutral on the landing? check at the landing fitting, or put both lighting circuits on one side of board live and neutral to check to see if its a shared neutral between down and up lights

 

[ianmacd]

Does it trip both RCD's (assuming lights are split across both)?

 

[meady]

I had the exact same problem a while back and it turned out to be a shared neutral as mentioned. I spent ages trying to find the problem :-(

 

[ITS]

I've now put both lighting circuits on same RCD side and a few more lights work (So definitely a shared neutral between lighting circuits in their case) but some lights still trip it.

 

[ianmacd]

What if you switch off all the mcb's apart from the lights ones and does it still trip?

 

[kme]

Had one a while ago where LV spots were returned on the ring main neutral!

Than was fun when the ring was on an RCBo.......

Had to feed the relevant lighting cct through the RCBo supply, as the neutral connection is under a laminated floor - nothing to be done until they change the flooring, or move.........

 

[ITS]

After an investigation today, I've discovered neutrals mixed with CPCs, CPCs used as Lines, Neutrals borrowed from god knows where (probobly next door) - so I've started rewiring today. Thats the only way I can walk away knowing its all OK.... I'm too old for this ****.

 

[ProDave]

After an investigation today, I've discovered neutrals mixed with CPCs, CPCs used as Lines, Neutrals borrowed from god knows where (probobly next door) - so I've started rewiring today. Thats the only way I can walk away knowing its all OK.... I'm too old for this ****.

That's why many recommend a PIR before a CU change so you uncover this sort of fault before you swap the CU.

Hopefully in this case the customer is understanding and happy for you to do the work, but you can get the awkward ones that say "it all worked fine with the old fuse box" and don't expect to have to pay to have faults corrected.

P.S I hope you don't really mean "CPC's used as LINES" do you? I've seen bodge jobs with CPC used as neutral (for a timer fan) but I've never seen a CPC used as line.

 

[kme]

I hope you don't really mean "CPC's used as LINES" do you? I've seen bodge jobs with CPC used as neutral (for a timer fan) but I've never seen a CPC used as line.

No???

Callout a couple of weeks ago by my plumber. Fairly involved heating system on a new build (gas boiler, unvented cylinder, 4 channel programmer, zone valves for DHW, towel rads, upstairs rads and downstairs UFH (5 zones)....okay?

He checked with the sparx that they were ok with this - they said "no problem".

When he came to fit the boiler (utility room) and cylinder (1st floor airing cupboard), there were no cables to be found, and one thermostat fitted downstairs - six were supplied!

He called them, and they came and "retro wired" the system - off 3 seperate fused spurs (1 for programmer, 1 for boiler [both in airing cupboard], and 1 for UFH manifold in utility). Remember this bit, it`ll be important in a minute.....

So, the sparx have wired it up - customer switches on DHW on Friday afternoon.

When plumber goes to get paid on Monday morning, customers lay into him verbally. The central heating has been blasting out all weekend - they can`t shut it off (why they didn`t think to turn the switch on the front of the boiler is beyond me! but they HAD turned off one of the fused spurs.)

Plumber says "electrical". Sparx say "plumbing" - so he calls me:

this is what I found:

Have a look at the flexes into the wiring centre.....

2 spurs & programmer.

UFH manifold wiring

The CU install (remember - new build!)

:yellow card

All the 3 core flexes had CPC used for switched live - wiring well stuffed up. Ripped out, restarted (CH only). No certs on site. Had to use wireless stats for the UFH - upped the cost a bit

 

[ProDave]

Hey, at least he sleeved the CPC in brown sleeving

That's not quite as bad as using the CPC of t&e as live though is it.

 

[a1spark]

Yes Prodave , they are about in places

I came across a t&E to an exterior mounted Shutter switch....Connections as follows...

Red : Live feed to shutter switch

Black : S/L to Shutter motor "Up" connection

cpc [ with black insulation tape where exposed from sheath] ..S/L up to Shutter motor "Down connection

and, therefore, of course, no protective conductor provision to the metal shutter switch box in the street either !!!!!

:_|

a1 spark

 

[batty]

Yes Prodave , they are about in placesI came across a t&E to an exterior mounted Shutter switch....Connections as follows...

Red : Live feed to shutter switch

Black : S/L to Shutter motor "Up" connection

cpc [ with black insulation tape where exposed from sheath] ..S/L up to Shutter motor "Down connection

and, therefore, of course, no protective conductor provision to the metal shutter switch box in the street either !!!!!

:_|

a1 spark

Must have been the same bloke that wired the gates up on the job i'm doing at the moment. None of it was earthed at all and a piece of 2.5 tw/e is being used to feed motor of gate which needs a 4 core so it goes backwards and forwards the cpc is being used for one of the live cores.

 

[batty]

That's why many recommend a PIR before a CU change so you uncover this sort of fault before you swap the CU.Hopefully in this case the customer is understanding and happy for you to do the work, but you can get the awkward ones that say "it all worked fine with the old fuse box" and don't expect to have to pay to have faults corrected.

P.S I hope you don't really mean "CPC's used as LINES" do you? I've seen bodge jobs with CPC used as neutral (for a timer fan) but I've never seen a CPC used as line.

Have seen tw/e used as three core on two way switching a few times that reminds me went to a job a few years back with lighting circuit tripping out main Rcd had just this. Told the lady it needed rewiring gave her a price but never heard no more and she did not pay the bill for the call out either.

 

[ianmacd]

Debate starter (playing devils advocate), had a quick look at the regs on identification of cables and it says:

1) g/y singles shall only be used as a protective conductor and not over-marked (514.4.2 with the exception of a PEN)

B) Does not state g/y can not be used as anything but Protective conductor in multicore cables when over-marked (in 514.4 anyway)

iii) Does not state bare wire can not be used as anything but Protective conductor in flat cable when over-marked (in 514.4 anyway) although it is described in BRB as insulated and sheathed flat cable with protective conductor so maybe 514.4.2 requires it to be g/y and therefore only used as a protective conductor

I will agree that using something any normal person or sparks would believe to be a protective conductor as anything else is not very smart at all and goes down to bad design IMO anyway regardless of if it complies or not.

 

[ProDave]

On the subject of bare protective covers, has anyone come across t&e with the CPC actually sleeved green and yellow?

I have. I found some once on a property I was modifying. The ring final was wired in red / black t&e, but instead of the CPC being bare, the whole length of the CPC was sleeved in very thin green / yellow insulation.

I've never seen it before or since, and never seen it on sale, but someone, somewhere must have made it once.

 

[ITS]

P.S I hope you don't really mean "CPC's used as LINES" do you?.

Yes I do. The 2way switching was wired in 1.0mm T&E with one strapper wrapped in loose red insulation tape.

 

[Adrian41uk]

On the subject of bare protective covers, has anyone come across t&e with the CPC actually sleeved green and yellow?.

Yeap, in Exhibition Land. Not sure who makes it, but its used by the drum load at NEC/Earls Court etc for wiring of exhibitions stands. Saves time too... no looking around for the sleeving & ensures that it isnt missed off.

Adrian

 

[Evans Electric]

Must say I have seen loads of room stats wired in T/E , with the bare earth sleeved and used as N and sometimes as S/W .

 

[PC Electrics]

You cannot use the bare cpc as a live conductor because it's not insulated and there's a reg says all live conductors must be insulated.

Yes, have seen very old t&e with cpc 'insulated' with a thin green layer.

I've seen relatively new CH installs with 3 core flex with g/y used as a switched live. It's not as if 4 core is hard to get or expensive, is it really? No excuse really.