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Topic Title: Illuminated light switches
Topic Summary: Neon connected live to earth
Created On: 20 February 2013 05:31 PM
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 20 February 2013 05:31 PM
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breaker

Posts: 280
Joined: 05 October 2006

As the title says a neon indicator illuminated switch has been installed on lights feeding W/C's in a village hall to show whoever is locking up that the lights are still on. However the installer has connected the neon indicator across the switch wire to earth because there is no neutral present and they probably couldn't be bothered to rewire or run a neutral to the switch. My question what are the implications of this as I have been asked to carry out an inspection here and I'm not sure how you would code it as I've never seen this done before and certainly wouldn't do it myself. The installation is TN-S and there is not an RCD on these lighting circuits.
 20 February 2013 06:05 PM
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aligarjon

Posts: 2848
Joined: 09 September 2005

we used to connect the neon across the line and switch line years ago. The neon would be lit when the light switch was off. back feeding across the lamp filament so long as it wasn't blown. maybe you could persuade them to swap them over.

Gary

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Specialised Subject. The Bleedin Obvious. John Cleese
 20 February 2013 06:25 PM
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breaker

Posts: 280
Joined: 05 October 2006

Yes but I think that would confuse matters and I don't think it would work with the 28W 2D fittings with electronic ballasts that have been installed.
 20 February 2013 06:28 PM
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Thripster

Posts: 639
Joined: 22 August 2006

Typically, there is a 120-270k resistor in series with the neon. Work out the current andthen decide whay, if any, iimplications there are........
 20 February 2013 06:50 PM
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mrcornbeef

Posts: 247
Joined: 05 December 2005

How can you test for insulation resistance if you did it would fail code 2 my opinion
 21 February 2013 07:07 AM
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Fm

Posts: 680
Joined: 24 August 2011

You would remove sensitive equipment prior to testing
 22 February 2013 07:31 PM
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mrcornbeef

Posts: 247
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Originally posted by: Fm

You would remove sensitive equipment prior to testing


Agreed but you would expect them connected live and and neutral not live and earth , what would you code it if you came across it bearing in mind it could fail and cause a fault to earth ??
 22 February 2013 08:35 PM
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breaker

Posts: 280
Joined: 05 October 2006

I personally think it's a poor job that's been done and as I've already stated I wouldn't even consider doing it myself but is it immediately dangerous, I'm not entirely convinced it warrants a code 2 but that's why I'm asking the question.

Mrcornbeef if there was an RCD in this circuit surely it would see it as a fault and trip anyway, if the neon or resistor failed how would that cause a fault to earth when how it is now, in my opinion, is effectively already a fault to earth.

It just don't seem right to me but I struggling to see how I can explain the reason why it possibly needs a code 2 or 3.
 22 February 2013 09:05 PM
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impvan

Posts: 772
Joined: 07 September 2005

This neon is a load, intentionally fitted between Live and Earth.
Now if you found, say, one of the fluorescent fittings intentionally wired between Live and Earth, you'd certainly know how to code that!
 22 February 2013 09:05 PM
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mrcornbeef

Posts: 247
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It has got to be code 3 min can,t see how it is to regs unless other guys no different ??
 23 February 2013 06:59 AM
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ebee

Posts: 5711
Joined: 02 December 2004

It`s not usually a problem.
OK it will show up in testing.
If its all working correctly then no problem an RCd will not trip on the low current passed by this circuit which is often in milliamps.
The problem is the potential for failure - if these components fail then you are introducing a danger just like the mains tester screwdriver .

Is the "Amnesty" still in force ? LOL

I would not leave it connecting PH to E.

Either
1/ Disconnect it
2/ Run a N to it
3/ Connect between line & load for reversed type indication.

Actually when I said it`s not a problem I was thinking with filament lamps not fluorescents.
CFLs might slow strobe with this in place across the switch terrminals

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Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 23 February 2013 08:43 AM
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maltrefor

Posts: 121
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Originally posted by: impvan

This neon is a load, intentionally fitted between Live and Earth.

Now if you found, say, one of the fluorescent fittings intentionally wired between Live and Earth, you'd certainly know how to code that!


And how would you code an RCBO with an earth tail then?
 23 February 2013 02:56 PM
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breaker

Posts: 280
Joined: 05 October 2006

I would say a RCBO is designed to be connected through the 'functional earth' whereas a neon indicator lamp is not nor is any other form of light fitting or appliance in this situation.

I'm pretty sure we would all agree it's not right but what reg does contravene?
 23 February 2013 03:05 PM
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daveparry1

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Agreed Breaker and what Maltrefor is talking about is something completely different! (functional earth lead on rcbo)

Dave.
 25 February 2013 12:32 PM
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AJJewsbury

Posts: 11502
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What if you found a capacitor connected L-PE? You usually see p.f. correction ones connected L-N, but interference suppression ones are usually connected across all three pairs of conductors. (L-N, L-PE and N-PE). Capacitors allow a small L-PE current to flow and like any component, could fail. Functional earths are recognised for some older data cabling RS 232 etc - I even knew some installations that would leave out the data GND connection and rely on the mains c.p.c. instead - as it reduced earth loops). So utilising a c.p.c. for things other than protection against shock isn't new, nor prohibited.

I'm struggling to see a fundamental safety problem with this neon arrangement. Yes, the 'return' connection from the neon is a functional earth - so strictly should be identified cream, but only as far as it joins a conductor serving as a protective earth, at which point the green/yellow identification takes priority.

- Andy.
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