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Discussion Starter #1
The source of this problem is in France, but I think that there is no national difference in this case.

We have a long hallway in which there are four light fittings which are all switched via a single bistable relay with several buttons along the walls. Most of the time it all works fine - but - -

Twice now we have had a blown fuse caused by the 'last' light in the sequence. This is a 20 amp fuse and of course goes with a bang. The problem appears to come from the low wattage lamp itself, which has sooty deposits around the base. Apart from soot on the casing the socket appears OK. The house is only rarely occupied and the lights have probably been used for only 100 hours or less. They are normally off even when we are in the house.

There is a 0.5 amp RCB in the main supply and this does not go - so there is no significant earth leak involved.

Coincidence would be the most convenient explanation of course but I wondered if anyone else had seen this behaviour at all, or had an explanation for it.
 

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Has the lamp been changed?

Could there be a defect in the relay apparatus?

Could there be a defect in the wiring?

There would have to be something close to a short circuit for the 20 amp fuse to blow.

This looks like a situation where you would have to take away something (for example unscrew that last lamp) and then wait to see if the problem still happens.
 

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This looks like a situation where you would have to take away something (for example unscrew that last lamp) and then wait to see if the problem still happens.
Yes, and the more often it happens the quicker Mr. Ower can determine if the fixes work.
For troubleshooting he may want to substitute a breaker.

BTW, a fuse "going with a bang" implies a severe overload and is probably not due to a fuse defect or fuse holder defect.
 

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The source of this problem is in France, but I think that there is no national difference in this case.

We have a long hallway in which there are four light fittings which are all switched via a single bistable relay with several buttons along the walls. Most of the time it all works fine - but - -

Twice now we have had a blown fuse caused by the 'last' light in the sequence. This is a 20 amp fuse and of course goes with a bang. The problem appears to come from the low wattage lamp itself, which has sooty deposits around the base. Apart from soot on the casing the socket appears OK. The house is only rarely occupied and the lights have probably been used for only 100 hours or less. They are normally off even when we are in the house.

There is a 0.5 amp RCB in the main supply and this does not go - so there is no significant earth leak involved.

Coincidence would be the most convenient explanation of course but I wondered if anyone else had seen this behaviour at all, or had an explanation for it.

I am in France { yeah I do go back and forth between USA and France } and I very well verised with French electrical system.

Now let start at began at the last luminaire as you mention soot around the luminarie socket if so look very carefull with the concats to make sure there is nothing touching out of the place and conductor connector block is good shape not show any damage like defourmed { out of normal shape }

BTW the RCD should trip but if you are on older French code the lighting circuit will not be on RCD that why it will not trip at all.

But some case ballast can go bad and do pretty good damage as well.

But somecase the cable between the relay to the luminaire can go bad also if you have some kind of critter been up in the attic area { I have see it couple of the time }

The other thing was this house pretty dry inside or pretty well humid inside ?

If you need more question or something just holler in here one of us will help you.

{ If you want me to translated to French I can do that but I will keep both Engish and French so that way other readers can understand what is going on }

Merci,Marc
 

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Discussion Starter #5
On closer inspection

Thanks for the suggestions.

I have, since the posting, had a look inside the control housing for the failed lamp and it seems that one component - probably a capacitor - has simply exploded, as capacitors do when they fail. There was shrapnel inside the housing and one bare piece of wire still attached to the base board. It looks like the component was across the input lines.

This is clearly the obvious cause of the problem - but why in the same position after such short time? It could be just a ropey batch of bulbs I bought of course.

It just occurred to me that there might be some transients which fly around when these things are starting up and perhaps they might occasionally get a harmful resonance of some sort.

For the moment I think I will go with the ropey batch diagnosis - unless someone knpows different of course.

Thanks again for the interest
 

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that one component - probably a capacitor - has simply exploded, as capacitors do when they fail. There was shrapnel inside the housing and one bare piece of wire still attached to the base board. It looks like the component was across the input lines.

so that tripped the breaker


but why in the same position after such short time?
With four fittings, each position has a 1 in 4 chance of blowing. Two consecutive failures at random in the same position gives odds of 1 in 16.

If you get a third in the same position hire an exorcist. :)

Capacitors could fail from overvoltage, high ripple current causing heating, or internal defects.
 

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I am new here..sorry to get off topic, but could "frenchelectrician" Marc, please contact me? I am not sure how to work this site, and you seem to know your stuff. I dont want to hijack this thread..just needing some help. Thanks, Joe
 

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I am new here..sorry to get off topic, but could "frenchelectrician" Marc, please contact me? I am not sure how to work this site, and you seem to know your stuff. I dont want to hijack this thread..just needing some help. Thanks, Joe

Ok and I found you on other thread and I reply it for you.

Merci,Marc
 
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