Why Does My Dimmer Light Switch Feel Hot to the Touch?

2016 Mar 11
Posted in: Electrical
Light Switch

First of all, is the dimmer switch hot or just warm?

It’s perfectly normal for a dimmer switch to be a little warm when your lights are on (or partially on). But if it’s hot, there could be a problem.

Dimmer switches get warm because they have electronic devices inside of them to take care of the dimming.

In this article, we’ll take a look at:

  • How hot is too hot for a dimmer switch?
  • The common problem that causes dimmers to get too hot

How hot is too hot?

In general, if the switch is too hot to touch for more than a second, it’s probably too hot.

Underwriter’s Laboratory (U.L.) allows a maximum operation temperature of 195°F for dimmer switches. But the average dimmer operates much lower, at approximately 140°F.

That might seem quite hot, but most of that heat is contained within the electrical box in your wall. The plastic plate on the wall doesn’t usually get that warm. 

But if your dimmer light switch is getting very hot, the problem is likely that…

Your dimmer switch is overloaded

Every dimmer light switch has a maximum load, measured in watts, that it can safely handle. If your dimmer switch is excessively warm, you may have too many bulbs running off it.

How to tell if your switch is overloaded:

1. Figure out the maximum load for the dimmer switch you have. 
The maximum load is usually found on the switch itself (you’ll need to take the plastic cover off). Most standard dimmer switches are rated for 600 watts for incandescent bulbs or 150 watts for CFLs and LEDs.

Light Switch Load
Example dimmer switch with a maximum 600-watt load. Photo credit: Reuben Saltzman, StarTribune

Note that the rating is reduced when installed next to another switch (or two) in the same electrical box. This is because you’ll have to remove a tab, which reduces how quickly the switch can dissipate (get rid of) heat.

Dimmer Switches
Example dimmer switches installed next to each other, with tabs removed. Photo credit: Reuben Saltzman, StarTribune

2. Add up the wattage of the lights on the dimmer switch
Add up the wattage of each bulb connected to the dimmer switch. For example, if the switch controls 6, 60-watt bulbs in your kitchen, the total wattage for that switch is 360 watts (6x60=360).

What to do if your switch is overloaded

If, after adding up the wattages of the bulbs, you realize you have too many bulbs on a single switch, you have a few options:

  • Upgrade the dimmer switch. Some dimmer switches can handle 1000-1500 watts. Upgrading the switch is the easiest option.
  • Change to LEDs or CFLs. LED and CFL bulbs use less energy than incandescents, which means you can usually have more bulbs on a switch. However, if you have an old dimmer switch, you may still need to upgrade it. Even LED bulbs labeled “dimmable” don’t play well with older switches.
  • Rewire the lights. You can split a group of lights to 2 or more different dimmer switches. This is the most complicated option and usually requires contacting a licensed electrician.

Still having trouble?

If you’re still concerned that your dimmer switch is running too hot or just want a professional electrician’s help fixing the problem, contact George Brazil. We’ve been serving Phoenix and the surrounding areas since 1955.