My lighting circuit tripped off tonight. The only lights switched on at the time were two ceiling units, each fitted with three 40W R50 spots, both of which were dimmed to about half illumination. This installation has been in place for some ten years and this has never happened before.
What might have caused it? Should I be concerned?
Many thanks.
What tripped? RCD RCBO MCB Have any of the lamps blown?
An MCB (Wylex NS B06). The property is a single-storey bungalow with jusy one lighting circuit.
No.
Checked that the load isn't quite tripping it into overload especially if you have any floodlights or PIR lights thereon?...
Any mice?
Not that I know about. But wouldn't a nibbled cable be permanently out of action? Once I reset the MCB, everything - by which I mean all the lights on the circuit, all on simultaneously - worked perfectly.
The total load on the entire circuit has been full-on many many times since installation with no problems at all.
Thanks for the thoughts.
Only if they had managed to nibble through the copper, if they have then I really don't want to meet your mice :-)
I hope that your problem isn't this one, but it is one that kept me "amused" for months.
I had repeated trips on a lighting circuit, but with hours and days between them. I eventually got fed up and tried to track down the fault. It turned out to be the live wire crossing over an earth wire behind a heat/light fitting in the shower room. The wires had been compressed together when the unit was fitted and over about 10 years had finally worn through both insulations. I can only assume that occasionally due to heat, or some reason unknown, they moved close enough to short together. To add to the "amusement" sometimes the RCB would trip and sometimes the individual MCB.
I hope yours is much simpler.
FWIW a neighbour with a similar intermittent problem suspects that condensation creeping behind a fitting on tiles might be the culprit
You have been lucky then. Depending on the sensitivity of your trip circuit a failing spotlight fairly often generates enough earth leakage to take down the circuit. Surprised you didn't have a blwon one when you powered back up. Sometimes they do manage to self arc weld and heal when power is restored but expect it to go again and soon.
Probably not. Spotlamps seem to bring our kitchen lighting circuit down about one time in three that they blow and with four the the things that is quite often. I am experimenting with LED replacements now that decent powered ones are available that will survive in the fixture...
I had a similar problem a few years ago. The problem was overheated wiring in the ceiling immediately above one of the fittings. The short circuit was intermittent.
2.5 mm would be a challange to a mouse. 1.5 mm or 1 mm not so much. May find fried mouse with teeth embeded across L and E...
Trapped wiring in an accessory box some there is quite likely. Could be anywhere switch box, ceiling rose, any junction boxes.
If any lamp blows this can occur, maybe you have a fried mouse somewhere? grin
Brian
squirrels can also nibble cables. and 2.5mm is no problem to them.
I did: I was mistaken last night when I posted that all the bulbs were still working. It's a mild relief to know that this alone could have caused the trip (though individual bulbs have blown before without having the same effect, so I suppose it's just possible that it was a coincidence). It seems that I'll only have to go hunting for deceased wildlife if it continues to happen with all the bulbs OK.
Many thanks to everyone who responded.
I used to think this problem had gone, now that none of my lamps are filament lamps anymore. However, I've recently had two CFLs fail at end-of-life by shorting out (different makes). In both cases, the tubes had reached end-of-life and probably started running in cold cathode mode, and I suspect extra power was drawn through the internal PSU and caused a failure which shorted out the supply, such as one of the switching transistors shorting.
One of my (expensive) experiments with a mains LED replacement blew up in a spectacular fashion and tripped the MCB. Was only a 40 watt equivalent too. Which lasted for a lot less time than a tungsten in the same fitting.
I don't see how you can get earth leakage when a bulb fails - most don't have an earth anywhere near the actual bulb. What is far more likely is the bulb short circuits when it blows. Many have an internal fuse to try and limit the fault current - but this may not act fast enough for the MCB.
Earth leakage?, from where to where Martin..
Yes. LED units don't get as hot as filament bulbs, but they still get hot enough to kill themselves far too quickly. I doubt we will see anything retrofittable in old luminaires that is anywhere close to custom designed LED fixtures in terms of reliablity. The custom ones with decent heat sink designs are finally getting there at last!
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