Spotlights continually blowing!

[danrich123]

Hi,
I installed 12 downlights in a cellar around 12 months ago, all mains GU10 fire rated fittings. However, the GU10's just keep blowing...not immediately usually after a few days, and not always the same lights. I've been back a number of times checked the circuit, checked all connections, etc, even changed a few of the fittings, but they just keep blowing. I've put in most makes of GU10's, and have now just changed them all for low energy 9w's lamps and within 3 days 3 have gone.

Any ideas?

 

[bongos]

What voltage did you measure at the property? A high supply voltage could be causing a problem. The maximum permissable is 253vAC. Although a supply this high could cause problems for lamps rated at 230vAC.

Assuming the lights are recessed in the cellar ceiling, is the ground floor subject to kids jumping up and down on it?

Any external influences to take account of?

 

[electronicsuk]

Further to the above, is there sufficient ventilation to allow heat to escape from the lamps/fittings? I doubt this is the problem if CFLs have failed on you, but nontheless...

P.S. Were the CFLs you fitted manufactured by anyone reputable? A mate of mine fitted some cheapies from CPC in his kitchen (approx £3/lamp), and they were failing within the first week.

 

[ltheb]

Surely a voltage DROP would be causing the problem - drawing too much current? Any way I've never measured a voltage higher than 245v...
Many fire-rated fittings recommend the use of aluminium reflector lamps - usually referred to as 'coolfit'
I've recently had callouts for lamps blowing very quickly with both GU10's and MR16' (12v)
On the ELV side I found the problem was actually the lampholders: poor contact = no light or overheat. I replaced the lampholders and all lamps with Osram aluminium reflectors (from memory Screwfix code 88148 10,000 hrs) - waiting to hear back from the customer.
We have recently tried down rating a commercial installation where there were many 50w GU10's on a single circuit by using some low energy Osram lamps I bought from Screwfix rated at 40w (cat. 82717 - couldn't get them anywhere else from stock and even Screwfix didn't have any in their central warehouse) - so far, so good

 

[electronicsuk]

Surely a voltage DROP would be causing the problem - drawing too much current? Any way I've never measured a voltage higher than 245v...

No, a voltage drop would not cause this problem, as it would not cause the lamps to draw more current. The filament has a (relatively speaking) fixed resistance once warm, so I = V/R applies.

A loose termination causing rapid fluctuation in supply voltage could cause the symptoms mentioned, but OP says all connections have been checked for tightness.

 

[ltheb]

Mostly agree, though if R is constant and V reduces, then of course I increases, but agree this probably isn't significant here. No I was thinking more that it's fairly unusual for voltages to go through the roof but very common to find that hundreds of watts have been added to rooms where the original circuit was designed for a single nominal 100w pendant! The post about vibration is also a good one.

 

[flameport]

if R is constant and V reduces, then of course I increases

Of course it does NOT.

With a fixed resistance, reducing the voltage will reduce the current.

 

[ltheb]

Sorry, you're right - either the calculator goes or I do!

 

[danrich123]

Hi,
Checked the Supply voltage steady at 236v. Plenty of air circulation above lights. Checked the holders and none have any signs of burning/sparking.The new lamps installed were made by Eveready...never heard of them.
There may be a problem with vibration...above the cellar is a salon so lots of walking about.
I've advised them that there is nothing electrically wrong with circuit (cellar lights on own circuit) and their options are to try better lamps or try a different type of lights.
So they are now expecting me to purchase and fit new lights at my cost...but i no longer see this as my problem, do you agree? or is it my responsibility to give them what they want?

 

[Steve]

Hi,
Checked the Supply voltage steady at 236v.

Good.

Plenty of air circulation above lights. Checked the holders and none have any signs of burning/sparking.

Good.

The new lamps installed were made by Eveready...never heard of them.

They make cheap zinc chloride batteries.

There may be a problem with vibration...above the cellar is a salon so lots of walking about.

So this is a fire barrier between two properties? But you said . . .

Plenty of air circulation above lights.

Where are the fire hoods?

I've advised them that there is nothing electrically wrong with circuit (cellar lights on own circuit) and their options are to try better lamps or try a different type of lights.

Have you tried good brands of filament lamps? Or good brands of CFLs for that matter.

So they are now expecting me to purchase and fit new lights at my cost...but i no longer see this as my problem, do you agree? or is it my responsibility to give them what they want?

Its a tricky one. Theoretically you should be able to return the lamps as faulty, but proving it, and reclaiming your labour charges will be hard.

 

[GaryMo]

But you said . . .

Plenty of air circulation above lights.

Where are the fire hoods?

Hi,
I installed 12 downlights in a cellar around 12 months ago, all mains GU10 fire rated fittings.