We are putting light bulbs on a large outside tree in a city park. We
have six 100 foot strings of 100 C-9 lights. We have two 20 amp GFI
circuits available. I plan to put 300 lights on each circuit. My math
shows 2300 watts available and C-9 bulbs use 7 watts. This comes to
2100 watts. I will use 12 guage extension cords. The light strings
and bulbs are commercial grade. This all looks good on paper, but I am
worried because there is not much room for real world error. Does
anybody have experience with this many lights? Wasn't there a movie
about a guy causing a large scale blackout when he threw the switch on
his house decorations? I don't want to be that guy. Any help you can
give me would be appreciated.
As of this year I switched to LED 100%. Older bulbs are all retired.
Nicer sparkling colors and WAY, WAY less energy consumption.
When I used bulb I used flip-flop circuit to make lights
scintillate(looks nicer) and lessen the power usage.
This year I had a lot of LED lights (with pictures online at
http://notstupid.laughingsquid.com/winter.html , click to see a
fullsize picture), with more expected next year. There's still a few
things I don't have LED versions of, like the lighted, animated deer.
Yes. The colors shouldn't fade in 2-3 years like the incandescents do.
I haven't gotten to 100% LED yet, but do expect to use less than half
as much electricity as last year (when I had very few LED strings).
My setup is similar, with 2 out-of-phase flashing circuits, so one
(and only one) is on at a time (except the particular time I changed
the wires to take pictures). I do have a fancier flash, using an old
computer to flash them according to Morse code.
The normal rule is you don't put a load greater than 80% of circuit
capacirty itf it will be on longer than 3 hours.
Christmas is usually when the NEC goes on vacation though. If you
spread these out across 6 cords, plugged into the receptacles directly
I don't really see a huge problem thouigh since, technically it is a
700w load and a 1400w load on each, not a 2100w load. The circuit
itself should take it.
Fortunately circuit breakers do not take holidays off. They are only rated
for a maximum of 80% continuous load of 3 hours or more. Depending on the
age, quality, and condition of the circuit breakers you may not get them to
stay on for that long. That's about 16 amps for a 20 amp circuit.
Thanks for the input. I have an electrician coming out to inspect the
whole set up, but if you experience a brown out about 7:00 pm (MST) on
Friday after Thanksgiving you know what happened.
John Grabowski wrote:
I think I remember that from "National Lampoon's Christmas Vacation"
and the blackout ended when someone at the power plant threw a switch
labeled "Emergency Nuclear Power".
That was followed by someone saying "Don't look directly at the
I have used 300 around my house, but that was divided among 3 circuits
(shared with other lights). I consider the load to be 6A per 100.
That's a little safety margin.
18A load from lights might be too high for one circuit, considering
the extra current drawn by lights when they're cold.
Mark Lloyd wrote:I hel;ped my neighbor a griswald type a few years ago.
He was using his main plus a sub panel drawing over 120 amps. We had to
balance the loads since breakers were tripping.
He got a near 1000 buck electric bill and now does nearly nothing.
He had made the news and created a traffic problem but I miss it.
He offered to do it again but power it from my home...
He literally lit up the neighborhood!
On Mon, 20 Nov 2006 04:00:54 +0000 (UTC), firstname.lastname@example.org (Don
I was really thinking "9" in C-9 was the watts but the way they rate
things these days I wouldn't bet on anything. I doubt the quality
control is that precise to start with. The safest bet is 3 circuits if
you can come up with another 20 amps somewhere.
I found this link which answers all my questions. The chart says 7
watts and max of 274 lamps per 20 amp circuit.
Thanks for the input
I have used a very simple dimmer that was just a diode (half-wave
rectifier). This sort of thing allows to you get twice as many bulbs
on the same circuit (connect half to positive, half to negative.
They're never on at the same time).
Of course you'd need a diode that can handle that current.
C9 is a designation of bulb style/shape and diameter, and not wattage.
C means "candle flame shape". The "9" means maximum overall diameter,
in 1/8ths of an inch (meaning 1.125 inches).
C9, A19 and things along these refer to bulb shape/diameter.
There is a letter designation for bulb shape, and a number designation
of bulb diameter in 1/8's of an inch.
A has 2 stories behind it, 1 saying "arbitrary" and 1 meaning "average".
A lingering story is that "average" is between "PS" (see below) and "S"
B is supposedly "Blister", but some sort of oval shape.
C means "candle flame" shape.
E means ellipsoidal.
F means a flame shape - maybe more bottom-fat than C.
G means globular/spherical.
GTL means an incandescent penlight bulb having a short tube protruding
from a spherical bulb with the short tube having a lens.
K is some specific reflectorized bulb design that I sense as being good
for more compact incandescents.
PAR means "Parabolic Aluminized Reflector" - traditionally a narrower
PS is "pearshape" - usually a higher wattage bulb that has a tubular
"neck" between the base and the "main bulb portion".
R means "reflectorized bulb" - usually a floodlight or spotlight design.
S is a shape more common for some automotive types of bulbs and some
more ancient designs of bulbs - "S" means "straight-sided" - like an "ice
T means any of a significant variety of tubular shapes, for both
"single-end" and "double end" lightbulbs! May include some Philips ones
from production lines previously owned by Westinghouse, as well as
whatever else (bigtime available) is "T-bulb"!
- Don Klipstein ( email@example.com)
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