Watts vs. Dim Level

[prnorton]

Has anyone ever tested an X10 lamp module to see how the watts vary with the dim level? For example, if I have a 100 watt bulb dimmed at 50%, is the actual consumption 50 watts?

[mmn]

I've wondered this too. But I wonder if the consumption isn't the same. The lamp uses 50% and the dimmer burns the other 50%.

Regards
Michael

[tenholde]

the dimmer does not 'burn' the other 50%. Dimmers work by clipping off a portion of the 60-cycle sine wave, thus dimming the light and lowering the power consumption as well.

tenholde

[mrhappy]

Has anyone ever tested an X10 lamp module to see how the watts vary with the dim level? For example, if I have a 100 watt bulb dimmed at 50%, is the actual consumption 50 watts?

It is close but there are no doubt going to be losses in the dimmer circuit (heat) and then inaccuracies of the metering device. I did try it and as I say it is roughly what you would expect but I doubt close enough to try and guess what sort of power consumption the house was using (if that is what you were trying to do).

[langenet]

I did a test using an LED bulb by Phillips. The full on consumtion as read by my kilowatt meter was 10 watts. When I dimmed it to 50% it did go down to around 6 watts or so as far as I can remember . So the clipping of the sine wave has a definite impact on the overall consumption.

Rob

[drozwood90]

Also, depends on what dim unit you are using. UPB, Z-Wave, Insteon, X10, all use different amounts of power.

As pointed out, the unit itself will consume some power.

--Dan

[Uncle Michael]

Another complication is that the output vs. voltage for an incandescent lamp is strongly nonlinear. In fact, at 50% power input, light output is typically only about 20% of full power. 50% light output occurs at about 80% power input.

LEDs and CFLs are much closer to linear. So the match between the chosen dimmer and the characteristics of the lamp will affect at what point a perceived 50% dim level is achieved and the amount of power required to achieve it.

http://www.designingwithleds.com/tes...mp-evaluation/

[mfisher]

Has anyone ever tested an X10 lamp module to see how the watts vary with the dim level? For example, if I have a 100 watt bulb dimmed at 50%, is the actual consumption 50 watts?

Funny you should ask - quite a few years ago I wondered this very thing and did some tests. I tested 40w, 50w, 60w, 100w and 200w bulbs dimming with a SmartHome LampLinc 2000STW dimmer and measured the wattage using a Kill-a-Watt meter. I later checked these measurements against several different dimmers (from different manufacturers) and found them to be almost the same.

The top graph shows actual watts consumed at each dim level for each different wattage bulb, while the lower graph shows dim level vs % of rated wattage for each.

As you can see in the top graph, these lamps never reach their full rated draw at full-on, and all of the dimmers I tested jump from 0 to 15% at the first dim level, which is normal for triac-based dimmers.

In the lower graph you can see that the relationship between dim and watts consumed is not exactly linear, but is pretty close. At 50% dim the draw is about 60% of full rating.

So, to answer your original question: not exactly, but pretty close.

[Dave W]

This should be a sticky. Is great information.