Dining room bulbs keep taking out the main 5a fuse

[McGraw]

Hi.

We have 5 light fittings downstairs. They are three bulb chandelier type in the living room and hall, four bulb in the dining room, a single bulb under the stairs and a three bulb IKEA one in the kitchen with low wattage (think they are led).

When we have more than two bulbs in the dining room then there is always a chance one will go and plunge the house into darkness. This happens whether any other lights are on or not. It happens more often with four bulbs than with three.

I thought it might have been wired up badly last time we decorated but it wasn't and I think it had been happening before then anyway.

We have just had the dining room ceiling replastered due to a leak (we have had a leak like this before many years ago so maybe that hasn't helped?) So I removed the light fitting. After a while the hall light popped and did exactly the same...it has never done this before.

Can anyone suggest what might be causing this? Would switching to led bulbs help at all? We use normal 60w filament bulbs downstairs apart from the kitchen I think.

Thanks very much.

 

[mattylad]

This is very common with multi filament bulb fittings.

Switch to LED bulbs.
If bayonet fitting, Asda are currently doing them for £4.17 each.

 

[McGraw]

Great thanks a lot will go led.

 

[ericmark]

What is tripping the MCB or RCD. I wonder if your talking about the RCD and if you have a neutral ~ earth fault. Never seen it with lights but we have not had lights with RCD protection until 2008 so considering you say you had a leak it could be.

It also could be simple overload. In the main the lights are limited to 6A as the ceiling rose is only rated at 6A and is used as a junction box. So at 230 volt that is 1380W so it is a simple case of reading the bulb wattage and adding them up. My house 24 + 58 + 6*8 + 10 * 3 + 40 + 18 + 9 + 5 + 11 + 16 + 11 + 11 + 11 + 4 * 50 = 490W so no where near the point where it is likely to cause an overload even with all lights on. So if happens in my house must be the RCD or serious fault.

A RCBO is a RCD and MCB combined really hard to tell which function caused the trip. So try and tell us a little more. Bulb sizes and exactly what is tripping.

 

[bernardgreen]

When filament in a lamp bulb failes it can produce a cloud of metal vapour which conducts and creates a plasma discharge in the lamp. This is effectively a dead short hence the fuse blows. Some lamps do have a fast acting fuse built into lamp that should blow before the fuse / MCB in the fuse box blows / trips.

 

[McGraw]

OK thanks for further replies.

Absolute Max wattage is 11x60 filament and 15w led downstairs. There's another 2x60w in the master bedroom and bottom of attic. There's a further 2x energy savers in the other bedroom and landing. Finally there are three strip lights in the attic.

The bulbs in the dining room can pop when there are no other lights on in the house.

Does this help? Would a pic of our electric cupboard be any use?

Just to reiterate, the hall lights never go normally, its as if the fault moved down to the next fitting when the main dining room light was disconnected.

Thanks

 

[ban-all-sheds]

The bulbs in the dining room can pop when there are no other lights on in the house.

That's because their failing, or not, is unrelated to any other lights being on or off. Same applies to all the lights in the house.

Just to reiterate, the hall lights never go normally, its as if the fault moved down to the next fitting when the main dining room light was disconnected.

Well, unless you're suggesting that your lights are haunted.....

 

[ericmark]

When filament in a lamp bulb failes it can produce a cloud of metal vapour which conducts and creates a plasma discharge in the lamp. This is effectively a dead short hence the fuse blows. Some lamps do have a fast acting fuse built into lamp that should blow before the fuse / MCB in the fuse box blows / trips.

I would say Bernard has told you the problem. I found Ikea bulbs don't have the internal fuses so ionisation when the bulb blows seen as a bright flash will likely take out the MCB. Using LED bulbs will likely cure the problem not because they use less power but you don't get ionisation when they blow.

But I would not buy bulbs from Ikea. I have had problems before using Ikea bulbs.

 

[JohnW2]

I would say Bernard has told you the problem. I found Ikea bulbs don't have the internal fuses so ionisation when the bulb blows seen as a bright flash will likely take out the MCB.

With the sort of (momentary and very high) currents we are talking about, I don't think one could be very confident that one would get discrimination, even if an 'internal fuse present'. It is in the nature of fuses that they take a finite time to 'heat up' to the point of rupturing in response to the sudden appearance of a very high current.

Kind Regards, John

 

[bernardgreen]

Using a current transformer and storage scope to measure the current the measured values when the filament snapped were in the hundreds of amps but for less than one half cycle.

The filaments snapped to order by placing a magnet near to the lamp to make the filament vibrate and snap.

 

[JohnW2]

Using a current transformer and storage scope to measure the current the measured values when the filament snapped were in the hundreds of amps but for less than one half cycle.

I can believe that, but it would not surprise me if 'hundreds of amps' through a B6 could result in operation in well under half a cycle (the published curves do not usually go far enough to to be sure!) - so, as I said, I wouldn't be at all confident that one would get discrimination between 'an internal fuse' and a B6.

Kind Regards, John

 

[ban-all-sheds]

With the sort of (momentary and very high) currents we are talking about, I don't think one could be very confident that one would get discrimination, even if an 'internal fuse present'. It is in the nature of fuses that they take a finite time to 'heat up' to the point of rupturing in response to the sudden appearance of a very high current.

For years I used lamps with those fuses, reputable makes such as GE, Philips, Osram....

For years I never had the MCB not trip when one went pop. OK - it's a 5A Type 1, not a B6, but even so....

 

[JohnW2]

For years I used lamps with those fuses, reputable makes such as GE, Philips, Osram.... For years I never had the MCB not trip when one went pop. OK - it's a 5A Type 1, not a B6, but even so....

Amidst those double negatives, I think you are agreeing with me!

Kind Regards, John

 

[ban-all-sheds]

Indeed.

There's only 1 pair of double-negatives.....

 

[JohnW2]

Indeed. There's only 1 pair of double-negatives.....

. but that was enough to mean that I had to read it three or four times before I was confident to reply!

Kind Regards, John