How Many LED Bulbs can I run in series?

March 13, 2014
Can I successfully use C7 LED Christmas Light Bulbs with threaded brass base in strings of 50 bulbs and if so, how many strings can I attach together?  -Brian
Hi Brian,
The C7 LED bulbs can fit into any standard E12 (candelabra) base socket wire.
For LED bulbs the maximum length of cord that you can run is not determined by the power draw of the bulb or the number of bulbs but the maximum run length of your cord.
That maximum run length is determined by manufacturer’s specification for maximum connectivity for the cord.
For example, 18 AWG wire cannot be run more than 250 feet – even with LED bulbs installed.  Over 250 feet in a series, linear run, the wire itself is at a maximum current rating just based on it’s own resistance.  So, you’d have to use a splitter and establish another circuit – or run another extension cord.
For this reason, on our 100-foot cords, we sell them with only one plug installed.  We suggest you run them out from a splitter in a T formation.  Our 50-foot cords are wired the same way – with a single plug.  Our 25-foot cords have two plugs and their maximum connectivity is 2 strands since they are constructed with 20 AWG wiring.
If the 250 feet limitation won’t work for your installation, you might consider our pre-wired LED sets that feature 3-wire engineering that allow you to run up to 80 sets in series.  Max connectivity is noted on each item.
For all scenarios where you are customizing cords and running longer lengths of 18 AWG wire, use the services of a master electrician.
Hope that helps.  Let me know if you have any other questions.

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