spotlights and flourescent lights

[trwb99]

Hi,

I have just bought some bathroom spotlights, and the instructions say not to fit them in the same lighting circuit as a flourescent light, which I intend to fit above a mirror in the bathroom.

Anyone have an opinion on whether this is ok? And what do the mean by 'same circuit'? The lights will be on the same loop from the CU, but come from different junction boxes.

Cheers

Tom

 

[breezer]

i bet is because of the back emf caused when the flourescent tube "stikres"

in plain english, when the flourescent light turns on a very high voltage (several thousand volts) this may "upset" your other lights transformer

 

[felix]

That sounds about right to me too. A fluorescent starter works by drawing current through the inductive ballast and tube filaments. After a short delay, a bimetal strip inside the starter heats up and breaks the circuit. The resulting high voltage spike from the inductor causes the tube to strike but some of that spike may come out onto the supply cable.

The spotlight manufacturers have possibly had one of their transformers go pop when it was wired close up to some beefy fluorescent light so they want to play safe. Since this is a small fluorescent light and not connected directly to the spotlight transformer you can probably ignore the warning. The snag of course is that if your transformer does go bang, for whatever reason, it will be your fault. If it was mine I would go right ahead.

PS: This problem never existed when a transformer was an iron core with two coils on it.

 

[trwb99]

Thanks very much, I'll do it and let you know if my house blows up!

Cheers

Tom

 

[ban-all-sheds]

PS: This problem never existed when a transformer was an iron core with two coils on it.

That's what a transformer still is.

I'm sure what you meant to say was "This problem would never affect careful buyers if the manufacturers accurately described their products as 'cheap, nasty and flaky 12V power supplies' rather than 'transformers'"

Where's our IBL evangelist, BTW?

 

[felix]

Quite right. The things sold as transformers are, in reality, switch mode power supplies. I have just one of these excuses for a transformer and some day I'm going to get a scope on it and see exactly what's coming out of the 'secondary'.