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[tom j]

Hi ya guys quick question if I dim my lights using a timer say to 40% and I'm using a 100 watt bulb will that be the equivalent of burning a 40 watt bulb trying to save on my energy bill and didn't want to use a CPF in this application but would like the saving of a 40 watt bulb with the ability to ramp it up to 100 watts when necessary. Thanks

Tom j

[JeffVolp]

While dimming does save energy, it doesn't work quite the way you think.  An incandescent bulb becomes much less efficient as it is dimmed.  There are probably curves that will give you exact numbers, but my WAG would be turning down a 100 watt bulb to 40 watt equivalent would probably still consume around 60 watts.

We do have an otherwise dark interior hallway where we do pretty much what you describe, except we start with a 40 watt bulb, and it is dimmed to a nightlight level overnight.  I tried a dimmable CFL in that location, and it was still much too bright during the night.

Jeff

[tom j]

While dimming does save energy, it doesn't work quite the way you think.  An incandescent bulb becomes much less efficient as it is dimmed.  There are probably curves that will give you exact numbers, but my WAG would be turning down a 100 watt bulb to 40 watt equivalent would probably still consume around 60 watts.

We do have an otherwise dark interior hallway where we do pretty much what you describe, except we start with a 40 watt bulb, and it is dimmed to a nightlight level overnight.  I tried a dimmable CFL in that location, and it was still much too bright during the night.

Jeff

Hi thanks yep I guess I was way off track but that's why I asked, Thanks!!! I was thinking about a dimmable CFL I afraid I don't understand though why was there to much light when you dimmed it can't you dim it down to complete darkness like a incandescent?

Tom j

[JeffVolp]

I don't understand though why was there to much light when you dimmed it can't you dim it down to complete darkness like a incandescent?

Most dimmable CFLs are supposed to go down to 20%.  The ones we have were still too bright at minimum dim - before they started to flicker or just go out.  This is for an interior hallway outside bedrooms, and we only want a dull glow at night.

Jeff

[gil shultz]

40% Dimming

Your idea is basically correct, watts are watts.  What you do not take into account is the color shift and brightness of the lamp.  For your location you probably do not care.  The simplest answer is dim it to what you like, you will be saving energy,  There is also another side effect, dimming the light bulb increases the life of the filament dramatically.  This is because the tungsten filament is operating at a lower temperature and will not boil off as rapidly.  The black on older light bulbs is on the inside and is tungsten that boiled off the filament and deposited on the colder bulb. 

If you use a Halogen lamp the life of the lamp probably will be greatly reduced.  The reason is that the filament has to be at a minimum temperature for the halogen cycle to work.  The halogen cycle re-deposits the boiled off tungsten back on the hot filament in the presence the appropriate gas in the lamp, the early gas used was halogen hence the name.

A inexpensive way to get a long life bulb is buy one rated at a higher voltage such as 130V - 145V for a 115 volt system, much cheaper and basically the same thing as a long life bulb.

Good Luck
Gil Shultz

[dave w]

If you use a Halogen lamp the life of the lamp probably will be greatly reduced. 

Good Luck
Gil Shultz

FWIW
Gil, Not entirely true, based on how much you dim.

Once you dim the halogen below about 3200 kelvin you are boiling off filament at about the same rate as a regular lightbulb, so loss of re-deposition has little effect. Dimming to 40 or 50% would still greatly extend bulb life whether halogen or standard large envelope bulb.

I have many 50W halogen spots that are dimmed to 30% for four hours every night. At least four of them are pushing 10 years.

[TakeTheActive]

...if I dim my lights using a timer say to 40% and I'm using a 100 watt bulb will that be the equivalent of burning a 40 watt bulb...

While dimming does save energy, it doesn't work quite the way you think.  An incandescent bulb becomes much less efficient as it is dimmed.  There are probably curves that will give you exact numbers, but my WAG would be turning down a 100 watt bulb to 40 watt equivalent would probably still consume around 60 watts...

Quick Answer: NO.

SEARCH the Newgroup for posts from another X10 Pioneer - Dave Houston. IIRC, the time period would be several years ago when Dave posted a chart comparing DIM PERCENT to WATTS CONSUMED.

Agreeing with JeffVolp, and expanding a touch, a 100 Watt incandescent bulb:

• DIMMED to 50%
  
  
• will probably be CONSUMING 75 Watts
  
  
• and producing the light output (lumens) of a 25 Watt incandescent at 100% power
  

• Will your idea save you money? Yes.
  
  
• Will the bulb last much longer? Yes.
  
  
• Is it the most efficient use of energy? No.