light bulbs keep blowing...Why?

[timmy123]

I was called to a large pub today where they have 2 particular lighting circuits where the bulbs are failing/blowing on a daily dasis. The lights are all mains voltage ( none 12 volts). The 2 circuits are protected by 10 amp type C MCBs . I have added up the total wattage of lamps on each circuit and they are both around 1.5 kilowatts each.
The problem only started recently. The only recent change has been a new chandelier type light has been added to one of the circuits. This contains 6 x60 watt lamps and I have included this is the total load on each circuit. The client also tells me that he has not made any changes to the type/make of bulbs he is using.

Every time a bulb blows it is tripping out the MCB on its circuit. There are no RCds involved.Each lighting circuits each has a dimmer unit and these units have been in place a long time prior to the problem starting.

Any suggestions would be greatly appreciated as the landlord is changing half a dozen blown light bulbs each day!.

Many thanks.

 

[sparkinlee]

My favourite theory when bulbs keep blowing for no apparent reason is to suspect a loose connection, arcing and effectively turning the lamps on and off. I don't know if this theory holds water, but it might be worth checking the connections, especially in the latest additions to the circuit...

 

[Electricalserv]

Are you sure the bulbs hes using are made for dimmers?

 

[nickblake]

poor quality lamps , , tripping when a lamp blows is quite normal this is due to the sudden decrease in the resistance of the filament thus causing a short circuit which causes the MCB to do its job and trip check the supply voltage and also do a Ze test if its a pme system there could be a neutral fault , this can cause peak voltages across phases and in the worst case scenario with a loss of neutral can cause 400 volts across fitting due to back feeding down the earth and back to the common connection the neutral bar

 

[kathwilcox]

check to see if the bulbs are from morrison's, if so throw them all in the bin!

 

[Deleted member 9648]

Ask him to write down the location every time he changes a lamp if no obvious cause surfaces.....had this sort of thing before and when you actually get the facts it turns out they are not changing nearly as many lamps as they tell you.
As the others have said,if they are blowing look at the quality of the lamps before delving any deeper.

 

[Adam W]

How come the lighting is all on type C breakers?

 

[Deleted member 9648]

How come the lighting is all on type C breakers?

Any reason they should'nt be?

 

[Adam W]

Any reason they should'nt be?

I always thought it was at least 'conventional' to use type B unless there is need to accommodate higher inrush currents, eg for motors. I would have thought that using type C instead of B would reduce the likelihood of tripping when bulbs blow, or alternatively you could argue that it's masking the real problem.

 

[telectrix]

as long as he's not been treating the bulbs with miracle glow.

 

[UNG]

Had a few problems similar to this where the voltage was above 240v with lamps rated at 240v blowing frequently changed to 250v rated lamps and the problem was reduced to acceptable limits

 

[Goody]

check to see if the bulbs are from morrison's, if so throw them all in the bin!

Do large pubs shop at Morrisons too? LOL.
Must be a lose connection somewhere on the line! :confused5:

 

[Knobhead]

The accountants have probably got a job lot of crap lamps on the cheap. Not unusual in industrial/commercial situations.
On one plant I was normally ordering 1 box of lamps a week, so when the crap lamps arrived I had to up the order to 2 boxes. All the electricians were fed up of lamp changing so I upped the order to 4 and threw 2 in the skip each time. It wasn’t long before the accountants noticed and asked what was going on. We were soon back to good lamps again.
Accountants, penny wise, pound foolish!

 

[UNG]

Do large pubs shop at Morrisons too?

I think they buy from the cheapest source they can as with a lot of businesses margins are very very tight at the moment

 

[UNG]

Accountants, penny wise, pound foolish!

Seen a lot of businesses screwed up by accountants and buyers who work on the principle "Never mind the quality Look at the bottom line price"

The public authorities "Best Value" policy is a similar thing where price rules over what they buy