Customer Question: Can I mix incandescent and LED bulbs on my C7 and C9 stringer wire?

November 18, 2020

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Here is a question I received today from John in Coloma, MI:

Hello…. Yesterday, I received my shipment of various-colored traditional “old school” C9 and C7 bulbs from an on-line order that I placed on your website approx 1 week ago. I am very satisfied with my order. These bulbs are placed on a special sign which I change to various colors depending on the season (Christmas multi-color,July 4, red white & blue; Halloween orange & purple; etc).

My specific question is… those “new-fangled” LED bulbs which are now all the rage (and which you offer on your site)… will the C9 and C7 LED bulbs fit OK into existing sockets on light strands that have always been previously used for the old-school traditional C9 and C7 bulbs?

I am interested in trying some new color combinations and “sparkly” effects that appear with the LED bulbs, but just am not sure if they are do-able in sockets that have always been specifically “geared toward” the traditional old school bulbs.

Also, I am concerned about any sort of odd power surges, etc that might occur if I do, in fact, retro-fit an old school strand/socket with newer LED bulbs. And so, again, can I use my existing strands for the LED bulbs?

And, if I can indeed just simply twist in the newer LED bulbs, need I worry about any weird unusual power surges? Thanks for your time and attention reading this. I look forward to hearing back from you.   John

Here’s our answer to his questions:

Hi John,

Yes, the new-fangled LED Bulbs that have E12 and E17 bases should work just fine in your C7 or C9 stringer wire.

The only time we’ve seen issues is when cords and bulbs have been custom made for each other (normally those you find as a loss leader in the big-box stores) and the sockets themselves were non-standard and wouldn’t have fit any retrofit bulb.

That also assumes that your C7/C9 stringer wire is constructed with an 18 AWG parallel wired traditional Christmas light cord. This parallel construction allows you to use high current (traditional incandescent) and low current (LED) bulbs in the same cord with no issues.

(Still wondering if your string is wired in parallel? If a C7/C9 light string stays lit when a bulb is removed, it’s wired in parallel.)

I suggest you use an outdoor rated surge protector with any LED Christmas light products because surges on your lines will be your LED bulbs biggest enemy.

Some other considerations for you to keep in mind:

  • Depending on the color, the LED lights mayl not “throw” as much light as traditional 7 watt bulbs and may look pretty different installed next to each other.  Start with a smaller order of LED bulbs and install them to test them out. Then you’ll be sure they’ll be a good fit for your sign project. I do know that they use the warm white C9 LED bulbs for a huge sign at the Memphis Flower Market and it looks impressive.
  • We just started carrying multi packs of LED bulbs so that should make it easier for you to test out designs that include those different colors.
  • If you are mixing traditional white incandescent bulbs and LED White bulbs – go with “warm white”.  It blends better with filament bulbs because they lean to the yellow end of the spectrum instead of the blue.

I hope that helps.  Let us know if you have any other questions!

Originally published on August 13, 2014. Edited and re-released November 18, 2020.

Shellie Gardner
Aside from throwing dinner parties that feature at least two kinds of cheese dip, Shellie's passions include travel, Mid-Century Modern furnishings and finding the perfect street taco. Has been known to snort laugh champagne.

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