Here is the third question from my interview:
For shorter sets of 50 or 100 lights, it’s true that you’ll need more extension cords to plug them all in (unless you’re using LED light strings).
Yes, you’ll need to either use the splitter at the end of an extension cord, a separately purchased splitter or an additional extension cord to avoid running more than the maximum number of lights in series than are specified for your set.
For example, let's say you have 10 sets of mini lights that have 100 bulbs per string with a maximum specification of 5 strings. If you are installing them on your Christmas tree, you'll need to split them into two 5-strand circuits. (Hide the plugs at the trunk and work your way up and down the tree.)
There are two specifications to be aware of when you are installing your mini lights:
Light string maximum connectivity rating
Don’t exceed the maximum connection rating for your sets of lights when connecting them end to end. This is usually printed on a tag installed next to the set’s plug.
Since different sets are manufactured with varying gauges of wiring, sets with the same number of bulbs can have different ratings. (So you can’t say across the board that if your lights have 100-mini lights you can plug in 5 sets of lights in a single run.)
LED lights can often be run 20, 30, 40, 80 strings in series. Always check your set's specifications to determine how many can actually be run in series. As with incandescent sets, don't make assumptions.
Because you can run more LED strings in series, you will need fewer extension cords when installing pre-wired LED sets - that is one of their best advantages.
In addition to the ratings of the light strings, don’t exceed 85% of the maximum rating of your household breaker. Consult with a master electrician to assist you with calculating the maximum power allowance per breaker in your service.
A good rule of thumb is not to exceed 1000 watts on a single household breaker. (Note that's breaker not outlet. Multiple outlets can connect to a single breaker so keep that in mind.)
So if your light strings are rated at 40 watts per string, you can run a maximum of 25 strings of that rating on one breaker.
Ultimately, consult with an electrician with questions specific to your installation.
When you purchase a string of lights make sure you know how many lights you can run in series and what the power rating in watts are per string so you'll know:
1. How many lights you can run in series?
2. What is the wattage (in watts!) of the string of lights