Vent, Valve & Volt
Light switch, dimmer or outlet warm to the touch

This is normal

Usually normal: a dimmer warm while in use

Dimmers shed some heat while they work. A dimmer that is warm only while the lights are on, with no smell, buzz or discoloring, can be normal.

Why this happens

Lutron says a dimmer's wall plate may normally feel very warm when touched while the dimmer is on, and that its dimmers are designed to keep surfaces below UL's 140 F (60 C) limit at full rated load in a 77 F room. Lutron also notes that when dimmers are ganged in one box and their side fins are removed, each dimmer's load rating drops. So a warm dimmer is fine only if it is not carrying more light than it is rated for.

What to do

  1. Keep using it, but feel it now and then. It should be warm, never hot or painful.
  2. If you recently added fixtures or bulbs on that dimmer, or it shares a box with other dimmers, ask a licensed electrician to check the load rating.
  3. If it ever gets hot, discolors, buzzes loudly, smells or stays warm with the lights off, turn the breaker off and call an electrician.

When to stop. Hot, painful, discolored, smelly, buzzing, or warm with the lights off: breaker off and call.

If it still worries you, tell the licensed electrician

  • The dimmer brand and model, and how many fixtures and bulbs it controls.
  • Whether it shares a wall box with other dimmers.
  • How warm it gets and how long the lights are usually on.

Build the full list: what to tell the licensed electrician.

Start this troubleshooter over

References (every fact above comes from one of these pages)
  1. Lutron: Dimmer heat (PDF)
  2. Mr. Electric: Why is my dimmer switch warm to the touch?
  3. CPSC Publication 518: home wiring (PDF)

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