I have a 6 light bulb bathroom fixture installed.
At present all bulbs are of course wired in parallel to the line.
I have a bunch of 60W speciality expensive bulbs I would like to use,
but only want to run them at 30W. Dimmer won't work here because I
have 2 fixtures like this on the same dimmer and this would be 600W,
much greater than its rating.
I can rewire the fixture so that pairs of bulbs are in series, thus
burning my 60W bulbs at 30W.
Question is that when I rewire them in series, one of the bulbs I'll
call number 1 will be wired to the line, and the ouput of bulb number
1 will be connected to the next bulb number 2's center. Thus number
1's base which is normally neutral/ground when in parallel, will now
be at half voltage because it is feeding bulb 2 and not going to the
Is this a code violation or safety concern ???
It would be a violation on several counts.
Consider this one scenario:
Owner removes bulb #2.
Owner now goes to remove bulb #1 (power is on but lamp is not lit).
In doing so, he touches the shell of the bulb. He gets full 120V
shock since bulb #2 doesn't even reduce voltage to 1/2 (which would
be bad enough).
Go for the dimmer, they make them to handle more than 600W. Leviton has
2000W dimmers for example.
I don't think they are still available, but you use to be able to buy
point source diodes that when in under the bulb. I believe they are no
longer available because they exposed the threads on the side of the light.
However I may be wrong and maybe you could find some of them, they dim 50%
one lamp at a time.
Probably against code; for reason Speedy Jim (and I) have given.
But also a point of clarification. (Forgetting for the moment
anything about increasing resistance in relation to the
temperature of the bulb filaments, colour of the light produced
by a dimmer bulb etc.) because you you may have already
experimented with this anyway?
Your 60 watt bulbs bulbs when operated at their 'normal' 120
volts draw 0.5 amps. 120 volts X 0.5 amps = 60 watts.
When operated at half their 'normal' voltage they will draw 0.25
When you wire them as pairs (two bulbs in series) each bulb will
be at half the voltage; 120 volts/2 = 60 volts.
Your 'new' wattage for each bulb will be 60 volts x 0.25 amps 15 watts.
Therefore your 6 bulbs will consume, approximately, 6 X 15 = 90
watts and will appear to much dimmer.
Presently if you put 6 X 60 watt bulbs in your fixture you are
consuming 360 watts.
In a nutshell half voltage means 'one quarter' the power
consumption. (This is the result of half the voltage and half
the current. A half times a half again = one quarter).
These observations are partly theoretical because bulb filaments
will probably have a positive temperature coefficient of
resistance. In other word as they get hotter, up normal operating
voltage their resistance will increase. Or, to put it another way
their resistance at half voltage won't necessarily be exactly the
same (cos they are cooler) than at full voltage; so the exactly
half current at half voltage may not be quite correct.
Not to nitpick but can you assume the bulbs in each pair are
identical; maybe it doesn't matter? Mass produced Christmas tree
lamps, in series strings, work OK.
An inexpensive lights dimmer/switch may be your best choice; but
some dimmers kick up quite an electrical racket (interference) on
TV and audio systems etc.
Two cents from here. Terry.
I have 2 sconces in the livingroom; each has 2 candle bulbs.
Code or not, each has the 2 15 watt bulbs in series. They go on
automatically via X10 module, everyday. It give the room a nice
glow without too much power. I could, I suppose, use the X10
module to put them on in a dimmed state, however, they've been
this way for 25 years and probably won't change soon.
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