does a dimmer save money?

Dumb question - I probably should know myself

Do you save money by having a light at 50% as opposed to 100% with the c-bus dimmers.

easy one for you guys to answer

 

I've also been told - from reliable sources - that running halogen lamps at 90% instead of 100% virtually doubles the lamp life.

 

Thanks Guys

The 90% idea is not a bad one. Probably not that noticable either

Mick

 

Does the slow start nature of dimmers also extend bulb life?

 

The soft-start on the dimmers definitely extends lamp life. The filament in tungsten lamps isn't subject to as much "thermal shock" when soft-started. Incandescent bulbs also have an in-rush current at turn-on because the filament is cold and at its lowest resistance when off. Notice also that most lamps fail at turn-on time and the soft start helps here.

Regarding the lamp life, most manufacturers make light bulbs to work in many places around the world. They will often make 1 design to work over the 220 - 240V range. That means that here in Australia with 240V the lamps are being used pretty hard and this shortens their life. Dimming them down a bit doesn't reduce the peak current or voltage on the lamp but it does reduce the RMS voltage the bulb sees and this does help.

Think of phase-controlled dimming like the lamp being turned off for a rest for a portion of the mains cycle, a bit like the way the heart rests between beats. The longer you can make the "rest" period of the bulb (i.e. dim the ligth down) the better for the bulb and hence the longer life.

 

but beware

Running a lamp at 90% definitely does extend lamp life and is barely noticable. Ive been doing this myself for the last 5 years or so but there is one draw back. You need to run the lamp at 100% every so often to 'burn-off' any build up on the glass within the unit. Halogen lamps are very different to incandescent (of course, you can't touch the outside of the glass or the oil from your fingers will cause a hot spot on the glass which will eventually cause the lamp to blacken and fail). Likewise, the transfer of metal on the glass relies upon it running at full load so as to transfer the buildup back to the fillament. If you every month or so, run the lamp at 100% for about 30 seconds, this should take care of this problem.

BTW, I've even applied this to a 500W (or should I say 450W ) halogen in my back yard which is still going strong after 5 years.

I achieve it by setting up the 'and' logic in the dimmer unit and applying a second common group address with a 90% level. No matter what light you switch on, it won't run above 90%. My burn-off is performed every month by using an area address which ramps all loads (including the 90% inhibitor) to 100% for 30 seconds then switches off, when I arm the security to leave the house.

Cheers