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Topic Title: Low energy lamps cause sparks
Topic Summary: I'm stumped can you suggest?
Created On: 23 November 2012 08:29 PM
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 23 November 2012 08:29 PM
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Zs

Posts: 2629
Joined: 20 July 2006

Hello,

I've spent the afternoon at my Mum's trying to sort out an ongoing issue with her porch light. It has not been working for a while and until today was on a photocell switch.

They had a low energy lamp in it. I have thought that I'd simply remove the photcell and its electronics and put a straighforward on/off switch on and the job would be done.

However, that didn't help so I have cut a hole in the ceiling to get to a junction and here is the information I have on the set-up and what is happening.

All cables test at >500M insulation every way. All junctions look perfect. Circuits test out properly with regard to voltage. it is a TT with a super low Ze involving two stakes and I installed the DB while they were away on holiday because I thought theirs was too high for them. Tested beyond belief because I love them so much.

The rest of the installation is not mine.

Feed (assumed) from DB to JB about 20 meters.

Three core from JB to a double switch. 4 m

Red feeds the switch with a permanent live.

Yellow returns the switch to the JB and serves the hall lights

Blue returns the switch to the JB and serves the porch light

All neutrals are picked up after the switch, back in the JB and onward to their destination light(s) maximum 2.

No permanent neutrals in the switch. All permanent neutrals are joined in the JB.

The hall lights (2) include 1 x downlight on a transformer which I removed from circuit so it can be discounted.

Even with no electronics. Put a low energy lamp in the porch fitting ( replaced to see if it was the cause, but not) and the low energy lamp flashes on switching and does not switch on fully. The junction box crackles and has sparked a few times.

Whilst the low energy lamp is in place the switched live registers on a voltsick as being on even if the switch is in the off position, and registers 230V between permanent and switched live, using a steinel combi.

So, in conclusion. There are no electronics on the circuit and only the insertion of a low energy lamp on the porch causes these issues.

I would not normally install with a remote permanent neutral but in all honesty I can't see how that would cause this.

I have left them with a normal switch and a tungsten filament with which they are happy, but I know they'd like some kind of control for light when they get home after dark. I want them to have that too. And a bag full of cakes and a secreted £20 note which is the kind of thing my Mum does. One day I will eat one of those hidden stashes by accident. Oh, and a pair of thermal socks.

Help! Why would 1 x low energy lamp cause such problems? I tried several different ones. There does not appear to be a borrowed neutral, and anyway, that wouldn't do this would it? Any suggestions?

Zs
 23 November 2012 08:57 PM
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cmatheson

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Is it possible your blue wires are crossed in the JB?

-------------------------
Chris Matheson MInstMC
 23 November 2012 09:14 PM
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AJJewsbury

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The junction box crackles and has sparked a few times.

Is it arcing just at one terminal (perhaps loose connection) or between terminals (swarf, loose strands (any flex?), damp/dirt)?

Whilst the low energy lamp is in place the switched live registers on a voltsick as being on even if the switch is in the off position

If it has been on recently, it's perhaps holding a little charge and back-feeding that onto the switch line (like getting a shock from the pins of the plug of and old CRT monitor - but hopefully with a lot less charge involved).

and registers 230V between permanent and switched live, using a steinel combi.

Thinking out loud now.. with the tester between L and SL, the CF should be presented with 230V (if through a high impedance, so at very low current), the electronics in the ballast should then switch-on and effectively tie the SL to N (like a filament lamp).

So far, my best guess is a loose connection in the JB - the rest might be explained by the old story of high impedance test gear being fooled by tiny currents.

(Other theories involved N on the TT not being close to earth - worth of one of Alan's tales - but Occam says not to go there yet).

- Andy.
 23 November 2012 09:40 PM
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Zs

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Originally posted by: AJJewsbury

The junction box crackles and has sparked a few times.


Is it arcing just at one terminal (perhaps loose connection) or between terminals (swarf, loose strands (any flex?), damp/dirt)?

I'm pretty sure the sparks came from the neutral terminal Andy.


Whilst the low energy lamp is in place the switched live registers on a voltsick as being on even if the switch is in the off position


If it has been on recently, it's perhaps holding a little charge and back-feeding that onto the switch line (like getting a shock from the pins of the plug of and old CRT monitor - but hopefully with a lot less charge involved).

Yes, it had been on and off lots of times. All I could get from a low energy lamp was a flash on switching it on and it never lit fully.

and registers 230V between permanent and switched live, using a steinel combi.


Thinking out loud now.. with the tester between L and SL, the CF should be presented with 230V (if through a high impedance, so at very low current), the electronics in the ballast should then switch-on and effectively tie the SL to N (like a filament lamp).

Interesting. Does this mean that activating the ballast, and then switching off at the switch still maintains a tie between permanent live and switched live? It stays like that though, In effect, a lowe energy lamp = 230V between live and switched live. I know it is realluy called the line but am stuck a bit in the old school.


So far, my best guess is a loose connection in the JB - the rest might be explained by the old story of high impedance test gear being fooled by tiny currents.

Definitely not a loose connection, first thing I wnet for when I heard the crackle, but I will change the JB for good measure before inserting one of those spotlight to downlight converters over the hole I had to cut to get to the JB. Do junction box terminals wear out even if they are tight? Agreed, the steinel is incredibly sensitive but the voltstick today was a fluke one and they are not so easily fooled. I also used my old draper voltage detector but I wasn't going to mention it because it is not GS38 and I have already been in trouble once this week for taking out a circuit using the megger.

(Other theories involved N on the TT not being close to earth - worth of one of Alan's tales - but Occam says not to go there yet).

we may have to. How close? The N on the incomer is about three feet from the top of the first stake. DB about 6 feet away from the incomer. Not only would I like to get this one sorted so that they may have electronic switching but I'm eager to know what is involved in this oddity. Up until last year it had been working fine, then intermittent faults, now it has gone completely wrong.


I don't like this, it is on my mind strongly. I am inclined to rewire, or at least run a temporary feed for testing. Do you think there is any mileage in doing so?

- Andy.
Thank you.

I can get back there to get any test readings you need (and lemon drizzle cake for all) and may already have them on the certs I did. But it might take a while because, yes, I am wood-graining an embassy staircase in South Ken from Monday so I will be making the most of a tiresome commute by staying late and listening to new music on the iPod whilst painting. Nice. Suggestions of new music welcome and looking for a totally stunning lady vocalist to listen to.

However, My Mum's circuit issues will be the most important in case you think they are dangerous.

Zs
 23 November 2012 10:05 PM
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AJJewsbury

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Hi Zs -
Definitely not a loose connection, first thing I wnet for when I heard the crackle

I don't understand how a nice solid connection can crackle & spark (sounds like a breakfast cereal!) - if it's not a screw loose might it be a broken wire just touching the terminal or something of that ilk? My gut feel is that the problem is there (well, the first one at least).

we may have to. How close? The N on the incomer is about three feet from the top of the first stake. DB about 6 feet away from the incomer.

Ah, no. Sorry, I didn't put that very clearly - not close voltage-wise I meant. Something like a neighbour with a L-earth fault and a broken RCD effectively earthing the supply L so causing N (as it's TT) to drift to a much higher voltage than normal. Alan's screwdriver in the flowerbed situations.

- Andy.
 23 November 2012 10:19 PM
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spinlondon

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Is it possible that you have a solid and stranded conductor terminated in the JB, and the solid terminal is keeping the screw away from the stranded conductor?
Has the terminal in the JB been overtightend causing it to crack?
Has the thread been formed correctly, does it go all the way to the bottom?
 23 November 2012 10:20 PM
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Cremeegg

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Depending on my mood any of the following can be totally stunning:- Annie Lennox, Barbra Streisland, Katie Melua, Randy Crawford, Adele, Alison Moyet, Carly Simon, Eva Cassidy, Joni Mitchell, Sade, Kate Bush, Patsy Cline, Chrissie Hynde.

As for the lighting - time to think about that one.
 23 November 2012 10:21 PM
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daveparry1

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If something in the JB is sparking/arcing there has to be a loose or broken connection in there Zs! Take all the wires out and refit them, maybe one of them is broken whithin the insulation,

Dave.
 23 November 2012 10:29 PM
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peteTLM

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not studied the previous posts but i reckon a high impedance path on the neutral. (between position and cu)
Have you done a R1R2 and compared with a RnR2?

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 23 November 2012 10:34 PM
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sparkingchip

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I went to sort out a light on a office building out of hours, three years earlier I had put a new photocell on a existing SON 70watt fitting and both had burnt out. I ended up fitting a Toolstation photocell the specification on the box indicated it was fine to work with a a new flood light I also ended up fitting.

But after a fortnight both the new photocell and burnt out, so I ended up getting a new combined light fitting and integral photocell from Wilts to replace them. To date I am about £120 down on the job and not sure of what the problem was.

Andy
 23 November 2012 10:48 PM
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michaelbrett

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Zs

Are you sure that there is no arcing between adjacent terminals due to damp or other adverse environmental conditions?

Regards

Mike
 23 November 2012 10:48 PM
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Zs

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I've done that Dave and situation remained.

But, I am still on the original bakelite JB so perhaps it is in the JB and you may be right. It feels tight and not like a crossed thread kind of tight., It looks tight. However, I trust you cos you work like I do. Spin, YES... there is a mixture of cores.

No question, I will change the JB as soon as I can and hopefully after work tomorrow so that I can get back on here, for wagos. I like that. I'll get back as soon as I have done it.


Cremegg...You chalk mark in a rain storm you, I have all of the above. Kind of looking for new/edgy in the absence of new Joni Mitchell. Just downloaded The Staves but I'm already not sure, and Tracy Bonham, likewise, but they may be growers. I'm working hard on that job but it will be the first diversion from all this physics in years. I need loud, pure music. Been feeling it for weeks like a deprivation so shall do it on all your behalves too. I'll leave it til next week before I tell it to you, but I'm rather hoping OMS will tell you a little story about shared music which caused him to get his butt whopped. He tells it so funny we ought to wait. OMS, will you tell us all the story about Gordon Please?

Edit: Mike, damp is not out of the question inside the roof of the porch and I have turfed out quite a few spiders. But it was all as new in the porch void when I left. I'm not discounting, especially as I have never seen the cable run from the DB. It is not a damp house but it is quire rural and very spidery. Significant fog tonight driving home from there, about 3m visibility so you may have a very valid point. Yours is plan B, Spin and Dave are plan A because a new junction is easier.

Zs
 23 November 2012 11:17 PM
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John Peckham

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Its the neutral at the fitting or the JB. Replace the Jb (s) with wagos in their own box. Use the grey ones with the orange levers. I will swap you a couple for your mums cakes that you don't eat from my stock?

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John Peckham

http://www.astutetechnicalservices.co.uk/
 24 November 2012 07:00 AM
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normcall

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Did you just tighten the terminals in the joint box or remake connections?
Low energy lamps and photocells or PIRs do not mix.

Action
Replace joint box, gently pull each wire with a pair of pliers to straighten then out and check for breaks and re-terminate.

Install relay between PE and lamp.

-------------------------
Norman
 24 November 2012 08:25 AM
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BillI

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Carbonised tracking in the surface of the bakelite JB? Change JB.
Just an idea dredged up from long ago memories, triggered by the word "Bakelite".

Bill
 24 November 2012 09:07 AM
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aligarjon

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I would do as John suggests, redo it with wago's. the screw may be tight but it could be done up on the insulation or be twisted up away from the connections as the screw has gone down. i have come across junction boxes where the screw doesn't go right to the base of the connection, relying on the size of the cable core for the last bit and it doesn't always make very well if the cores are different sizes or one is quite small, like a 1mm.

Gary

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 24 November 2012 10:02 AM
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Zs

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I'm liking the bakelite possibilities. The lamp holder is also bakelite but in very good condition and I've tested it repeatedly. However, tracking sounds feasible so I'll change that too later today. I'll do the JB/Wago change first.

It is cold. I wonder if the lamp would strike if it were summer?

I'm glad you're not coming up with any new scientific explanations yet. Or glimpses of different switch wiring. Sometimes I find it difficult to get my head around other people's switching, particulalry that done by the older electricians. Hence the quite big hole in the ceiling. Nice to be looking for the obvious. If this weren't a family job I'm sure the client would be questioning.

Back later to tell you.

The band was the wrong band...two blokes with a guitar and a set of bongos was not what I was expecting. Must check properly in future.

Zs
 24 November 2012 11:30 AM
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rocknroll

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The band was the wrong band...two blokes with a guitar and a set of bongos was not what I was expecting.



You mean an impromptu session for a few beers, commonly known as a 'pub jam session'.

regards

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"Take nothing but a picture,
leave nothing but footprints!"
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"Oh! The drama of it all."
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"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
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 24 November 2012 12:38 PM
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potential

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Originally posted by: Zs


I have left them with a normal switch and a tungsten filament with which they are happy, but I know they'd like some kind of control for light when they get home after dark. I want them to have that too. And a bag full of cakes and a secreted £20 note which is the kind of thing my Mum does. One day I will eat one of those hidden stashes by accident. Oh, and a pair of thermal socks.



Help! Why would 1 x low energy lamp cause such problems? I tried several different ones. There does not appear to be a borrowed neutral, and anyway, that wouldn't do this would it? Any suggestions?



Zs


If an ordinary tungsten lamp operates correctly I suggest the lamp holder is unable to make good contact with the low energy lamp.
 24 November 2012 12:58 PM
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daveparry1

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That wouldn't explain the crackling and sparking in the JB though potential!

Dave.
IET » Wiring and the regulations » Low energy lamps cause sparks

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