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I recently installed 2 ceiling fans with Lutron combination light and fan dimmer switches. On both circuits, if more than a half second or so is taken when selecting the fan speed (that is, a delay while between the low-medium-high states) the arc fault protection kicks in and shuts down the branch. There is no issue if I move fast enough between states or while the fan is in a steady state condition. This happens on two separate circuits with two identical fans and dimmers.

I'm going on the assumption that while the switch contactor is being moved there is either a small amount of arcing inside the switch or there is some EMI being generated that is offending the AFCI.

Should I go ahead and move to a non-AFCI breaker or are there any alternatives that I should consider?

  • Not sure what the internal circuitry of one of those switches looks like, so it's difficult to say for sure what's happening. When switches are opened/closed, there's a tiny spark that's produced. AFCI breakers know about this, and can ignore it. If you take a long time to move the switch far enough to break the arc, it's possible that the AFCI could call that an unsafe arc and trip. It's possible that holding the switch between states maintains an arc, which the AFCI does not like. – Tester101 Nov 12 '14 at 13:08
  • Ceiling fan speed is changed by using a multiple value capacitor to change the phase delay between AC current going to the various coils. One of your capacitors may have shorted out. -I'm talkong 20+ year old fans here. For all I know, the new ones come with a pulse width modulation DC power supply. -Different beast entirely. – Wayfaring Stranger May 19 '18 at 20:38
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Switches generate small, momentary arcs as part of their normal operation; AFCIs are designed to recognize and ignore these momentary arcs. However, holding the switch between positions (or taking a while to transition between positions) can lead to the arc sustaining itself, which damages the switch contacts and also causes the AFCI to trip because it sees an arc it doesn't recognize as harmless.

In other words: "Doctor, it hurts if I do this!" "Don't do that, then!"

  • a better quality switch can help – Skaperen Feb 27 '15 at 12:19
  • Yes it can, to a point -- holding it in an intermediate position is still not advised, though. – ThreePhaseEel Feb 27 '15 at 23:30
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NEMA maintains an "AFCI Unwanted Tripping Report" form at http://www.afcisafety.org/report.html . After reporting a problem there, I was contact and eventually send a new AFCI breaker that solved the problem, sort of.

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I had a ceiling fan that was tripping the Square-D arc fault breaker every time it was turned on. The fan was working perfectly while the electrician was here, and once he left it would trip the breaker every time.

Plugging a small LED nightlight into the other outlet serviced by that breaker completely eliminated the problem!

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