Timer Control for Outdoor Christmas Lights

By Dave Rongey - Summary:

How to Put Outdoor Christmas Lights on a Timer Switch: A GFCI device can protect a two wire strand of Christmas lights, so lets review how a GFCI device works while protecting outdoor Christmas lights and Holiday Display.

Controlling Outdoor Christmas Lights

Electrical Question: I have outdoor LED Christmas lights plugged into an outdoor extension cord, and everything works fine as long as I plug and unplug manually.

  • I got an outdoor timer and plugged the cord into that, and the lights turn on fine, but when they turn off, it trips the GFI.
  • I tried plugging the timer into an adapter and then the the adapter into the GFI receptacle, but the same thing happens.
  • Since outdoor cords and timers are grounded and outdoor holiday lights are not, how can outdoor holiday lights be run on a grounded timer into a GFI receptacle?

This electrical wiring question came from: Carol, a Homeowner from San Diego, California.

Dave’s Reply:
Thanks for your electric wiring question Carol.

How to Put Outdoor Christmas Lights on a Timer Switch

Application: Controlling Exterior Light with a Timer Control.
Skill Level: Beginner to Intermediate – Depends on the circuit wiring that is required.
Tools Required: Basic Electricians Pouch Hand Tools and Voltage Tester and a fiberglass or non-metal ladder.
Estimated Time: Depends on personal level experience and ability to work with tools and work from a ladder.
Precaution: Identify the lighting circuit or power source, turn it OFF and Tag it with a Note before working with the wiring.
Notice: Installing additional electrical wiring should be done according to local and national electrical codes with a permit and be inspected.

  • Christmas Holiday Lights and GFCI
    • GFCI’s are very sensitive where even a small amount of condensation or humidity may be building up inside the timer, even though it is rated for outdoor use.
    • Interior wall switches that operate exterior lights may be replaced with timer controls providing automatic operation. In such applications, the power supply to an exterior light may be extended using approved materials and methods thereby providing power to exterior lights, such as Christmas lights or other light displays.
  • Outdoor Extension Cords and GFCI
    • Your question about how a GFCI device can protect a two-wire strand of Christmas lights, (or any other device for that matter) is very understandable, so lets review how a GFCI device works while protecting outdoor Christmas lights and Holiday Display.

How a GFCI Outlet or GFCI Circuit Breaker Works

  • The GFCI Sensing Circuit
    Each GFCI device is made to sense current that has found a path to a grounded source.
  • Where a Ground Signal May Come From
    The grounded source can be a moist lawn, the concrete floor of a garage, a basement floor or a grounded water faucet.
  • How a GFCI Trips Off
    If the current passing through the GFCI device senses an abnormal condition where current is flowing to a grounded source it will trip and turn the the device off. This brings us back to the topic of the outdoor timer mentioned in this question, where there may be a fault with a component of this application or possibly the timer.
  • Arc Faults from Switches
    When a switch is turned on and off there will be an arc of electricity that occurs, and the size of the arc will depend on the size of the electrical load that is being placed on the contacts of the switch.
  • Christmas Lights and GFCI Circuit Size
    With this in mind, you may want to make sure that the electrical load or total number of watts being used by the LED Christmas lights is within the rating of the timer that you have because if the load is greater then this could be creating a problem with the time switch that is being sensed by the GFCI device.
I hope this helps you. Have a Merry Christmas!

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  • Wiring Diagram GFI
    The features and benefits of GFCI outlets and receptacles will give you a clear understanding of the importance why these safety devices are required by code to help protect you and your family against accidental electrical shock hazards.

Home Automation
Home Automation

  • Learn Home Automation for Controlling Outdoor Christmas Lights

  • Home automation is about delivering practical control of your lighting, home and personal lifestyle which provides comfort and control and energy savings.

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Great home safety ideas during holiday and anytime.

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FAQs Frequently Asked Questions and Comments

7 Responses to “Timer Control for Outdoor Christmas Lights”
  1. Kevin Fekety says:

    Thank You Very Much,


  2. Dave Rongey says:

    Hi Kevin,
    The indoor light timer should only be used for indoor applications. Outdoor environmental conditions may damage the timer and may create a hazardous condition. I would advise removing the timer and find an alternative means of control that is approved for outdoor applications.
    I hope this helps,

  3. Kevin Fekety says:

    I have installed Christmas lights on my house and plugged them into an Indoor Lighting Timer Control that is plugged into a ceiling outlet on the front porch. The lights turn on at the set time but will not turn off. Once the lights turn on the timer dial will not advance. What am I doing wrong ?

    Thank You for your help.

  4. Dave Rongey says:

    Hi Bob,
    Thanks for the Make and model number of the timer switch, however I was unable to locate the item online, however here are my thoughts about your project: Typically timer switches are made to be installed indoors. The electrical wiring may lead to indoor or outdoor light fixtures. If you would like to have the timer switch located outdoor then it would need to be installed into a weather proof enclosure, unless the time switch specifically states that it is rated for outdoor use and the time switch is enclosed inside a weather proof housing or enclosure.

  5. Bob Ruth says:

    I have an electric timer that I would like to use on Christmas outdoor lighting. The timer is described as being marketed by Toastmaster, Inc./Time Products Div., UL listed 159 B E 75984/1629039 Model No. 12-925, capacity 1875 watts, 15 amps/ 15 amps tungsten 1/3 h.p. motor/120 VAC 60HZ. The question is how safe is that for outdoor use during rain or snow? What precautions would you advise?

  6. charles nolan says:

    I would like to set up a electrical panel just for Christmas lites. How do I do that.

  7. charles nolan says:

    I would like to set up for Christmas lites next year. The way I do it now is out of house plugs and I keep tripping breakers.58N3


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