My light bulbs are making a ticking sound

[clickydave]

Hello all,

I've recently had an extension completed and as part of the work four light fittings in my original hallway were changed from normal incandescent ceiling roses into low energy fittings that only take fluorescent 'L1' bulbs (they have a base similar to a GU10 but longer). This was required to get the completion certificate on the extension.

I am happy with the fittings and the light output from the bulbs, however I noticed this morning that each of the bulbs is ticking rapidly whenever they are switched off. It is the noise you make when you gently tap your finger on the top of a keyboard button. Each of the 20 bulbs (5 per fitting) emits this sound and they are in-sync with each other at each fitting. When I remove a bulb and place it next to my ear the ticking sound continues for about five seconds then slowly fades away to nothing.

I'm not sure if this information is relavant, but I'm trying to include everything:

1) The noise stops when the bulbs are switched on

2) 3 of the fittings are on the upstairs lighting circuit, 2 are on the downstairs lighting circuit, both are on separate RCBOs

3) The downstairs lights are looped in at the fittings, the upstairs lights must be looped in at junctions in the loft because each switch and fitting only has a switched cable (Br + Bu-Br + GY). Looking at the wiring at a downstairs fitting it appears that the live to the fitting is after the switch rather than before it.

4) IANAE but I do have a multimeter and have done some basic checks at one fitting such as checking for any stray voltage between L/E and N/E which doesn't show anything (do you call it N/E or SwL/E?).

5) They may have made the noise for a while (the fittings have been up over a week now) but I only noticed it this morning. At the time the lights had been off for about 7 hours.

I have just a few questions:
A) Why are they doing this?
B) Should I be concerned?
C) Can it be stopped?

Thanks in advance for any help you can give.

 

[automationman]

Just to clarify:

1) The lamps tick when they are connected to the main lighting fitting when power is turned off at the light switch?

2) When you remove a lamp from the fitting in the off state, it continues to tick for about 5 seconds then stops?

3) You measured (with a multimeter) across switched live and earth but could detect no stray voltage at all? (light switch off)

4) You measured across neutral and earth (with a multimeter) and could detect no stray voltage at all?

Does your multimeter autoscale? or did you look down in the low volts region (under 10 volts AC) ?

 

[automationman]

Additional question:

Do the lamps tick when you turn off the consumer unit main switch?

 

[clickydave]

Your clarifications are correct. As to the multimeter, it is a Kewtech KT117 and was set to autoscale.

With the main isolater switch off there is no ticking sound (after five or so seconds).

What I can't understand is that obviously the bulbs must be getting some electricity in order to do anything - they are just light bulbs after all - and yet it seems all is ok. It is also affecting two different circuits which is confusing.

 

[AndyPRK]

I have had this too.

The bulb ticks in our porch when no power is applied.

Turn it on and it stops.

Sounds like a reed switch.

Drove me mad trying to work out where the noise was coming from!

 

[automationman]

I don't know the details of the lamps themselves. Do they have any electronics in them?

If no electronics then I suspect they have filaments that are essentially "tuned" to either transient noise or harmonics that are unintentionally modulated on the mains wiring from external sources.
Mains wiring carries many different signals at many different frequencies and harmonics of such fundamental signals. By chance the filaments in the lamps may have a peak reasonance at one of those many different frequencies. In the right circumstances a very small signal stimulus can cause significant resonance of a tuned circuit (such as a coiled filament wire)

If you feel confident (you have a multimeter so I assume you know what you are doing) and you are very careful then you could short switched live and earth at the lamp (using an insulated fused lead with clips)
See if that stops the ticking. Also try it with switched live and neutral shorted.

You can also try shorting neutral and earth (if you have an RCD at your consumer unit then depending upon your earthing system a link between earth and neutral may trip the RCD)

Don't forget to remove the short before you fflck the light switch on.

Obviously this will not fix the issue but it may narrow down the problem.

Questions:
Do you know what your main service earthing system is?
TNS (EARTH VIA OUTER SHIELD OF MAIN INTAKE CABLE)?
TNCS (PME)?
TT (EARTH ROD)?

With TNCS I would expect little/no measurable stray voltage between neutral and earth. With TNS I would expect something is most cases. With TT then anything goes depending upon how well your earth rod is installed.

 

[reggie perrin]

Are these low energy lamps and is the problem with 2-way switching?

 

[automationman]

apologies. I missed your original comment :

"were changed from normal incandescent ceiling roses into low energy fittings that only take fluorescent 'L1' bulbs"


In this case Reggie Perrin may be onto something.

 

[electronicsuk]

Are these low energy lamps and is the problem with 2-way switching?

Sounds like someone is onto the problem

I'd bet money on this being a problem with either 2-way switching or lack of CPC to part of the circuit, which is allowing capacitive coupling to charge the electronics in the lamps. I'd also bet that if you replaced just one of the lamps with a halogen or incandescent, the ticking would stop on the rest of the lamps controlled by the same switch.

 

[automationman]

[/quote]
I'd also bet that if you replaced just one of the lamps with a halogen or incandescent, the ticking would stop on the rest of the lamps controlled by the same switch.[/quote]


Yep, that would place a reasonably low impedance across line and neutral essentially grounding the coupled noise (grounding in the sense that neutral should be roughly at ground potential)

Yes, I guess a missing/open CPC may well allow capacitive coupling.

Though I regularly see inductively coupled voltage on adjacent wires when they are grouped together (at least I was assuming inductive coupling since I have never actually tested that theory)

 

[electronicsuk]

I'd also bet that if you replaced just one of the lamps with a halogen or incandescent, the ticking would stop on the rest of the lamps controlled by the same switch.

Yep, that would place a reasonably low impedance across line and neutral essentially grounding the coupled noise (grounding in the sense that neutral should be roughly at ground potential)

True, true - this would cause the ticking noise to cease regardless of whether the problem is related to capacitive coupling or your previous explanation re harmonics. However, I have to say that I think capacitive coupling is far more likely. We see people with similar problems on here all the time, although with less fittings is usually manifests itself as a flickering of the lamps.

Also...

By chance the filaments in the lamps may have a peak reasonance at one of those many different frequencies.

Unlikely. These are energy saving lamps, so no filaments. You also mention earthing, which should be irrelevant, as how many lamps require an earth...?

 

[automationman]

I agree, I failed to notice that the lamps are energy saving on that first response. Pity.... nothing quite like a resonance theory other than a conspiracy theory

Re the earthing, I was really trying to establish why there was no measurable voltage between neutral and earth. Even with TNCS I tend to be able to measure a few hundred mVolts between neutral and earth (because of voltage drop, other parts of circuit leakage to earth etc.) made me think that he has a disconnected CPC but not a cause/reason for the ticking.

 

[reggie perrin]

lol