Figuring Power Needs
If you have any questions or
concerns at all about electricity, please consult a licensed electrician
 |
| Typical 15 amp wall plug in
home |
| |
 |
| Typical 20 amp wall plug in
the office (notice the extra horizontal slot) |
You've
got thousands of Christmas lights yet you have no idea how many can be
plugged into a typical wall socket. We're here to help.
Let's use a simple electrical formula. Power (in watts) = Voltage
(in volts) times Current (in amperes) or P=VI which
is what engineers like to say (why "I" is an abbreviation for current is a
closely guarded secret by electrical engineering purists.)
In the United States, a typical wall outlet is 120 volts and all
Christmas light strings are wired to handle it. Your wall outlet is
usually wired in parallel to several others and connected to some sort of
circuit breaker or fuse, usually 15 or 20 amps. Your goal is to not
overload the circuit breaker/fuse. It's good practice to never put
more than 80% load on your breakers/fuses... strictly as a safety measure.
You will have to figure out if the outlet
where you want to plug in your Christmas lights is on a 15 or 20 amp circuit
breaker or fuse. The easiest way to find out is plug a radio in and
turn it up pretty loud. Go to you electrical panel and start turning
off circuit breakers or unscrewing fuses. When the radio stops making
noise, you're on the right circuit. The breaker/fuse will tell you how
much current that circuit can handle.
If you have a 15 amp circuit
with 120 volts and factor in an 80% load, using the P=VI equation
(P=V*I*0.8) you can have a total load of (120*15*0.8=) 1440 watts.
If you have a 20 amp circuit with
120 volts and factor in an 80% load, using the P=VI equation (P=V*I*0.8) you
can have a total load of (120*20*0.8=) 1920 watts.
Use the chart below to get a pretty good idea how much power different
types of Christmas lights consume. There are plenty of exceptions to
the chart since there are so many different types of lights. To see if
you're close, check the tag at the plug-end of a new string of lights and it
will tell you how much current it consumes... in most cases, it will match
up with the yellow column in the table and you can feel comfortable with the
numbers
|
Light String Description |
Lights /
String |
Total
String
Watts |
Total
String
Amps |
Total Strings
for
15 amp
Circuit
(80% usage) |
Total Strings
for
20 amp
Circuit
(80% usage) |
| mini-lights |
20 |
16 |
0.13 |
90 |
120 |
| mini-lights |
50 |
20 |
0.17 |
70 |
94 |
| mini-lights |
100 |
40 |
0.33 |
36 |
48 |
| mini-lights |
150 |
60 |
0.51 |
24 |
32 |
| mini-lights |
200 |
80 |
0.66 |
18 |
24 |
LED-lights
(C6-C7 look-a-likes) |
25 |
2.4 |
.02 |
600 |
800 |
| LED-lights (mini look-a-likes) |
60-70 |
2.6 |
.03 |
554 |
738 |
| C7 bulbs (5 watts each) |
25 |
125 |
1.04 |
11 |
15 |
| C9 bulbs (7 watts each) |
25 |
175 |
1.50 |
8 |
10 |
| 60 watt light bulb |
1 |
60 |
0.50 |
24 |
32 |
| Compact Fluorescent Light (equal to
a 60 watt incandescent bulb) |
1 |
14 |
0.12 |
102 |
137 |
| 100 watt light bulb |
1 |
100 |
0.75 |
14 |
19 |
| 150 watt floodlight |
1 |
150 |
1.25 |
9 |
12 |
rope
light at 5.5 watts
per foot and string is
18 feet long |
216 |
99 |
0.82 |
14 |
19 |
| Inflatable
Description |
Total
Watts |
Total
Amps |
Maximum
inflatables
for 15 amp
Circuit
(80% usage) |
Maximum inflatables
for 20 amp
Circuit
(80% usage) |
| inflatable (typical 4') |
52 |
0.43 |
27 |
36 |
| inflatable (typical 6') |
58 |
0.48 |
24 |
32 |
| inflatable (typical 8') |
80 |
0.66 |
18 |
24 |
| inflatable (typical 12') |
86 |
0.71 |
16 |
22 |
 Rule
of Threes: On just about every string of Christmas lights you
buy before 2008, it will have a sticker saying to never plug more than
three of them together in series. Don't try and bend the rules by
sneaking in an extra string or two. The wires powering those
little lights are small and not designed to handle a lot of electrical
current. Violating the rule of three's will get you blown fuses,
melted wire or a fire.
 Plugging
Plugs into Plugs and the Rule of Threes: You can always plug
the plugs into the top of other plugs. Theoretically there is no
limit other than the total amount of current being supplied... but it's
good practice to stick to the rule of threes... no more than three plugs
plugged on top of each other and never connect more than three strings
in series.
Always be on your toes when working with electricity.
Why? The stuff really can kill you. As an example,
click here for
a great video on arching. Want to see a guy get zotted by high
voltage... pretty gruesome, but it helps put things in perspective.
Click here by the high
voltage strike.
If you have any questions or
concerns at all about electricity, please consult a licensed electrician
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