Barn. Electric fence. Electric fence drifted a little too close to the non-electric fence and it started arc'ing between them with every pulse. Very small arc, across about 1mm.

No big deal - happens once in a while and is easy to fix.

BUT, this time, I happened to walk into the barn with all of the lights off while this was happening and I just happened to see all of my 100W LED flood lights pulse the very slightest of light ... with ... every ... single ... arc.

Why is this happening ? I do think these LED flood lights are on the same circuit breaker as the electric fence energizer, but of course they are also on a lightswitch and that lightswitch was OFF.

So how do my LED floods get a tiny little flash of electricity to produce a tiny little glow every single time the electric fence pulse makes an arc ?

No, this does not happen during normal (non arc-ing) operation.


  • OH - one thing I forgot ... the lights are not direct wired into the lightswitch like a normal household light. The lightswitch energizes a half-hot 20a receptacle in each location and the LED flood plugs into its respective outlet. So the circuit this all is on is a 20a circuit and the lights are just plugged into different 20a receptacles. – user227963 Jun 6 '20 at 4:39
  • It sounds serious. Electric fences only draw a few watts, you can run them on solar - so it's not like heavy load is dimming your lights. I suspect something is really gorped up with the site's grounding, neutrals etc. And you have luckily uncovered a dangerous condition that could kill you. – Harper - Reinstate Monica Jun 6 '20 at 5:08
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    Just to be clear - it is not dimming the lights - the lights are OFF. Lightswitch is OFF. The lights are lighting up very dimly and very briefly every time it arcs ... – user227963 Jun 6 '20 at 6:54
  • What I said still applies. I'm particularly concerned about your grounding system and N-G separation, as that's one system that'll interact with. Obviously this isn't The Problem Worth Fixing, but I suspect it's a "canary in a coal mine" for a serious problem that could kill you. – Harper - Reinstate Monica Jun 6 '20 at 15:37
  • Or at the very least, upset your animals. It's very common for a farm to have perturbed, stressed-out animals that avoid an area or refuse to drink from a [heated] water trough. I've heard of dairy farms where that severely impacted milk production. That's because farm animals are extremely good at detecting electrical leakage. – Harper - Reinstate Monica Jun 2 at 19:53

LED fixtures use a tiny fraction of the current of an equivalent incandescent lamp, and it could be that you're seeing induced current from adjacent wires. In other words, the arcing circuit is "transmitting" energy to adjacent wires and the LED circuits are "receiving" enough electrical energy to make some of the LEDs in the arrays glow dimly.

It's possible if you have an AM radio turned on you might hear the arcing fence through the radio from a mile away.

There may be other contributing factors, such as a poor ground connection to the fence charger, or maybe the LED circuits don't isolate both the hot and neutral lines at the circuit breaker.

Ideally you would have the wiring inspected by a qualified electrician in case there's a safety issue.

  • Thank you - appreciated. I will gladly have the wiring checked out, but you are of the mind that this is not a bad or broken wiring issue ? These are normal (not GFI or AFI) circuit breakers but wouldn't the breaker still trip if I was somehow connected Hot to ground ? Would an AFI breaker trip immediately when the fence arcs ? Just curious... – user227963 Jun 6 '20 at 19:31
  • It probably is not an arc fault directly from the hot line to ground. I suspect the current from the fence charger is creating a current in the LED circuits, like a radio transmitter. It seems to me it could possibly be due to broken down insulation or bad capacitors in the fence charger, or a mis-wired breaker to the LEDs. It might not even be dangerous (if it's just induced currents). I am not an electrician, so that's why I felt I should suggest consulting one. But I have seen LEDs glow dimly with very little current. – Tommy Trussell Jun 6 '20 at 21:51
  • Just a reminder: "very little current" to an LED, at 60 or 50 Hz AC can still be enough current through your body to stop your heart, so it's worth being careful. – Tommy Trussell Jun 6 '20 at 22:13

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