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Originally Posted by Graham
Pardon me for piggy-backing on this thread, but this reminds me of something I'd like to check.
I like my rooms well lit, so I use 150 Watt bulbs which get used a fair amount especially when I'm working. I'd like to use low energy bulbs instead, but they aren't available with that sort of effective output.
So is it possible/ safe to use eg two 13 Watt (75 Watt equivalent) or three 11 Watt (60 Watt equivalent) in a standard ceiling fitting?
Logically I can't see a problem, but I'd prefer to find out before I stick them in and stand back hoping the whole thing won't go bang!!
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You shouldn't have a problem. The rating given on a light fitting is usually there because of how much heat it can withstand. For example, a 100W light bulb gives off more heat than a 60W. As you are using low energy bulbs, you'll find heat is really not an issue.
The cable size in a light fitting is usually well in excess of what is required to carry the rated current of the protective device (5amp fuse or 6amp MCB), so the current taken by the bulbs is not an issue. Besides, low energy bulbs take far less current anyway (e.g. 11 watts = 0.05 amps approx., whereas 60 watts = 0.26 amps approx.).
BTW, if you want an approximate calculation of current for a given load use 4 amps per kilowatt (1000 watts). A more accurate way is to divide the rated power in watts by the voltage of the circuit (P/V). The rated domestic supply voltage being 230v (yes, 230 NOT 240.......those pesky Europeans made us change!
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