3core & earth problem

[sweet212]

Evening all,

Visited a customer yesterday who said their lamps were blowing regularly in the living room light fitting. I took the light fitting down and visually it looks fine. Its a metal fitting with 3 arms with an SES lamp holder on each. I removed the lamps and insulation tested the fitting with 999+Mohms as the result. All good. I then turned my attention to the wiring. R1 R2 from the light point to the board was 0.62. Insulation res for the circuit was 999+Mohms L-N, L-E, N-E, (lamps removed). Zs from the light was 0.88. Supply polarity is fine and the Ze is 0.22.

However there is a voltage of 58V showing from the SW line to earth when the switch is turned off.

The feed has been taken to the light point in t&e and a 3core cable has been taken to the switch. This is a permanent live, neutral and SW line back to the light. A live and neutral is needed at the switch due to a t&e leaving it to feed the kitchen light switch. I disconnected the 3 core either end and insulation res tested it. Again 999+Mohms was the result. When the permanent live is connected at the light point the SW line in the cable becomes live at 58V even though is completely disconnected each end.

I am returning tomorrow to have another look.

Any input would be helpful.

Regards

James

 

[Leesparkykent]

Capacitive coupling.

 

[sweet212]

Yes that is my thinking, but Ive not seen it on this scale. It is possible though because the permanent Line and SW line are the red and yellow cables. This will be my first port of call in the morning.

Thanks

James

 

[telectrix]

take an analogue meter with you.

 

[Octopus]

Regular blowing of bulbs should be remedied by fitting led bulbs .... Or not buying them from cheap outlets

 

[Deleted member 9648]

One of the most common domestic calls is 'lamps blowing all the time, must be the wiring'
99% of the time it's rubbish lamps and can be diagnosed and advised upon without a visit.

 

[PEG]

Evening all,

Visited a customer yesterday who said their lamps were blowing regularly in the living room light fitting. I took the light fitting down and visually it looks fine. Its a metal fitting with 3 arms with an SES lamp holder on each. I removed the lamps and insulation tested the fitting with 999+Mohms as the result. All good. I then turned my attention to the wiring. R1 R2 from the light point to the board was 0.62. Insulation res for the circuit was 999+Mohms L-N, L-E, N-E, (lamps removed). Zs from the light was 0.88. Supply polarity is fine and the Ze is 0.22.

However there is a voltage of 58V showing from the SW line to earth when the switch is turned off.

The feed has been taken to the light point in t&e and a 3core cable has been taken to the switch. This is a permanent live, neutral and SW line back to the light. A live and neutral is needed at the switch due to a t&e leaving it to feed the kitchen light switch. I disconnected the 3 core either end and insulation res tested it. Again 999+Mohms was the result. When the permanent live is connected at the light point the SW line in the cable becomes live at 58V even though is completely disconnected each end.

I am returning tomorrow to have another look.

Any input would be helpful.

Regards

James

Hi James,what device was used to measure that voltage?

 

[davesparks]

Why are you doing all those tests when the problem you've been asked to look at is the lamps blowing?

 

[Lucien Nunes]

Indeed. What was the supply voltage?

 

[andyb]

Lamps blowing will be one of 4 things
1, Rubbish lamps (most common reason)
2, Poor light fitting design, not letting heat escape.
3, High voltage.
4, They don't keep blowing, the customer dosn't remember which lamps they change.

 

[KEV 1 N]

Yeah, I often get asked "why do my bulbs blow all the time?" Usually there cheap pound shop stuff or the lights are on and off a lot. Wiring shouldn't cause them to blow, although if there's a lot of vibration on the ceiling above, that may affect the life of an incandescent bulb (I mean lamp, bulbs go in the garden!)......tell them to get LED lamps..

 

[Strima]

Bulbs grow, lamps blow...

 

[andyb]

If my client calls it a light bulb, it's a light bulb. Language changes over time.


light bulb | Definition of light bulb in English by Oxford Dictionaries - https://en.oxforddictionaries.com/definition/light_bulb

 

[Toneyz]

I assume that the lamps are of the halogen type and therefore the SES screw cap expands and contracts with the heat generated when left on for some time. This makes a small gap between the live contact pin and poor contact reducing lamp life.

 

[HandySparks]

...This makes a small gap between the live contact pin and poor contact reducing lamp life.

What do you think the mechanism would be for the reduced life under these circumstances?

 

[Toneyz]

What do you think the mechanism would be for the reduced life under these circumstances?

This is information given to me by a lamp manufacturer a few years ago.

 

[PEG]

What do you think the mechanism would be for the reduced life under these circumstances?

...I bet it has the word "sprung" in it...

 

[Des 56]

The problem is called modern living,its not in the makers interest to have the quality too high so that it destroys the market
Its like cars fridges,washing machines etc,the manufacturer needs to sell their product both now and in the future,the poor old wiring or fitting often gets the blame

 

[static zap]

As "sweet212" states "..... their lamps were blowing regularly in the living room light fitting............... "

Check the mechanical action of the light swich (if it hasnt be changed)

...some people gently use light switches
with mutiple loads can degrade contacts , doesn't show up every time /different user!
( Customer may not notice buzzing ... multiple on/off wear)

..but naff lamps /pooly fitted as per others comments....more common cause
( some fittings bake cheap lamps - look for arcing/black-dot on solder blob of bulb)

 

[telectrix]

I assume that the lamps are of the halogen type and therefore the SES screw cap expands and contracts with the heat generated when left on for some time. This makes a small gap between the live contact pin and poor contact reducing lamp life.

i blame it all down to these modern pesticides. how can a bulb flourish when it's bombarded with chemicals? no wonder we get things like this mutation.

 

[Des 56]

Nice to see you still have all your teeth Tel

 

[davesparks]

What do you think the mechanism would be for the reduced life under these circumstances?

It is not a reduction in lamp life, the poor connection of the spring contact results in the lamp not illuminating as there is no longer a contact with the live pin.
The uninformed idiot (householder) assumes that the lamp has failed as it has not illuminated and so replaces it. By replacing it they make a poor connection with the weak spring contact which lasts a short amount of time.
Then they replace the lamp again and the same thing happens.

 

[ashg285]

Go to a lot of jobs where its the bulbs, ask customer where did they get them from and a very common answer is the pound shop

 

[Deleted member 93172]

Bulbs grow, lamps blow...

Ha ha, I remember our old store man saying " Bulbs are for gardens - lamps are for light fittings sonny now what do you really want, if its bulbs your in the wrong ****ing shop".

 

[Paul P]

Best one I had was every bulb I fit goes bang. Looked at the lamp and it was a 110v one.

 

[dmxtothemax]

Lamps / Bulbs ?
Who cares what the customer calls them,
So long as they pay there bill
They can call it anything
Happy to take there money !

 

[DPG]

Their.

 

[telectrix]

Their.

now there's being pedantic, and their's being pedantic.

 

[dmxtothemax]

Don't speak English !
I speak STRAY-UN !

 

[sweet212]

Evening all,

Thank you for all the replies. I have since been back and corrected the problem. By swapping 2 of the cores over in the cable the 58V disappeared.

I also changed the Wilko lamps over for some Osram ones. Hopefully they will last a while longer.

Great knowledge and information shared by everyone who posted.

Thanks

James