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Sparks flew out of my breaker box, probably due to faulty wiring. In an effort to troubleshoot, I removed all the breaker and labeled them. Got a wire tracer and tried to trace the wires to see nothing was cross wired. Got a new 20amp breaker and reconnected one of the outlet that was 20amp. For test sake, I only connected one outlet. Getting a 118.5V reading, receptacle tester is reading correct, yet the fan won't turn.

Suspecting the wires or the receptacle it self may have been damaged, I take a new 14/2 wire, about 24 inches, connect the black to 20amp breaker, white to the neutral bar of the panel and ground to the ground bar of the panel. using a new outlet, I'm getting 118.5v reading and receptacle tester shows its correctly connected. Yet the fan won't turn.

Not sure what else to check. Do I new a new circuit panel? Please help.

The house is little over 40 years old and and the panel is just as old I'm guessing. The panel is Square D QO.

I'm a contractor and have worked with enough electricians and have basic electric skills and knowledge.

The fan was plugged in temporary for testing. The fan is not broken because I tested the fan at my neighbor's house and it works fine there.

I guess my question is can the circuit panel itself go bad, or could it have been damaged when the sparks flew? Everything but the main feed is disconnected so it's safe for me to do wire tracing. I haven't completed the all the tracing yet, but the ones I traced so far are not cross wired and appear correct. And, when I connect those back up with a new breaker and new outlet, get 118.5v reading, and receptacle tester is reading the wires are correct, the fan won't work. The only conclusion I can come up with is the panel has gone bad.

I'm probably going to get a new panel anyway since the house or the panel does not have a main shut-off, and I'm not about to start checking the connection of the panel itself without shutting off the power. But I do want to avoid having to pull new wires through out the house if possible.

So I guess it's now becoming testing for future knowledge, and maybe I can post what I find here for everyone.

So, here are the facts: - New 14/2 wire - Black is connected to a brand new 20amp breaker - White is in the neutral bar of the circuit panel - ground is is the ground bar of the circuit panel - other end of 14/2 is connected directly to one brand new outlet - multi-meter is reading 118.5V - receptacle tester is showing the outlet is correctly wired. - But connecting a fan I know works, doesn't turn on.

What else can I safely test until I get the power turned off on Monday?

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  • What make and model is your breaker box? Also, the fan is something you're plugging into the outlet you've hooked up temporarily for troubleshooting I take it? – ThreePhaseEel Jul 13 at 22:46
  • Hello, and welcome to Home Improvement. Where are you located, and do you have any electrician experience at all? And, you should probably take our tour so you'll know how best to participate here. – Daniel Griscom Jul 13 at 23:31
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    Photos of the panel, its bus bars naked of breakers, and anything around where the unfused feed connects would be helpful. THE FEED IS HOT - DO NOT TOUCH IT as it can kill you. Honestly I am a little concerned about your boldness:skill ratio, please be very careful! – Harper - Reinstate Monica Jul 14 at 1:53
  • @ThreePhaseEel The house is little over 40 years old and and the panel is just as old I'm guessing. The panel is Square D QO. I'm a contractor and have worked with enough electricians and have basic electric skills and knowledge. The fan was plugged in temporary for testing. The fan is not broken because I tested the fan at my neighbor's house and it works fine there. I guess my question is can the circuit panel itself go bad, or could it have been damaged when the sparks flew? Everything but the main feed is disconnected so it's safe for me to do wire tracing. I haven't completed the all the – ch1234 Jul 14 at 15:00
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    Just tested the temporary outlet. Hooked up the fan in one outlet, multimeter in the second outlet. As is, it’s reading 118.5v. I plug in the fan, still 118.5v. After I turn on the fan, it drops to 0v. How can this happen? – ch1234 Jul 14 at 16:54
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Big arc flash is big

Sparks flew out from your breaker box. Not from your meter pan, nor from a socket; from the breaker box. I assume you normally keep the cover on it and no gaps in the cover, so sparks getting around the breakers is actually a pretty big deal. This is a big arc flash.

So I would expect it to leave big evidence behind. And where I would look is

  • where the incoming power wires connect to the main buses (since you mentioned you don't have a main breaker -- is it a Rule of Six panel with a separate 8-12 space top area, and separate busing for the rest of the panel?)
  • where the main breaker bolts down to the buses (if you have one)
  • where the main neutral feed lands on the neutral bar (treat this as "hot", don't think it's safe because it's neutral)
  • Any of the branch circuit buses where branch circuit breakers clip on to the bus
  • Various connections on the neutral bar generally

I would expect a scorched main lug or burnt wires where the supply wire meets the lug.

Once the power is turned off, get the correct tools and try torquing down each of the lug screws. Pay very close attention to the amount of torque needed for the screw to start moving - you must do this "by feel", a click-type torque wrench is for setting torque, not measuring it. If any lug is significantly looser than another, then gotcha. Certainly do not do that with the power on; I don't know about you but all my hex sockets are made of metal :)

Then I would remove all of the wires from those lug screws, pull them back and inspect thoroughly for any sign of arcing damage. Any damage is call for replacing the lug and nipping back the wire just enough to seat it on clean wire. Don't fail to replace the lug unless physical inspection reveals it to be perfect.

QO is a fine, modern industrial tier panel and its quality is beyond reproach; however if a lug were improperly torqued, that would cause this. Reapply anti-oxidation paste to the aluminum wires and reattach. If you found improper torquing before, this should be the end of it.

If you are replacing the panel, replace with another QO so you don't have to buy all new breakers, unless there's some amazing feature of a competing panel that you really, really need. (Bolt-on-neutral and cheap generator interlocks are not two of them because QO has those).

Buy the biggest panel you possibly can

And buy a 40/42-space panel unless it simply will not possibly fit. The cost difference isn't that much over 20/24 space panels, and that assures you'll never ask "My panel is full. How do I add this circuit?" That is the #1 panel related question around here, and it's so easily avoided, and right now is the time to avoid it.

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  • But could a neutral being lost have allowed "a poor" ground to arc out (thus letting him see 120 on a meter), but not be able to carry current? – noybman Jul 14 at 22:20
  • Thanks for your response. I will certainly inspect for the burn marks after I get the power turned off. I was going to buy Square D Homeline, because I was going to replace all the breakers with new ones anyway. Figured new clean breakers with new clean panel. Maybe even pull new wires if I can tough it out in the small HOT attic space. I've tried to compare the QO and homeline, but aside from cost, I couldn't find a review that specifically said QO is better. It;s more of a preference. Should I go with QO? – ch1234 Jul 14 at 22:21
  • That's called "throwing parts at a problem" - and it's a complete waste of resources. Homeline is exactly what it says on the tin, a line intended only for residential use, to hit the (slightly) lower price-points sought by builders buying at high volume. The euphemism is 'builder grade' but it means cheapie. They won't even sell Homeline to industry. – Harper - Reinstate Monica Jul 14 at 23:14
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    Getting rid of the old Rule of Six panel is a blessing. What I mean @ch1234 is the chance of 20 QO breakers all being bad without looking bad is highly improbable. (and they don't "fail deadly"; if they did, they'd have a rep like Challenger or Zinsco.) I'd expect any QO problems to be visibly apparent either at the screw, or at the clip that grabs onto the stab. – Harper - Reinstate Monica Jul 14 at 23:33
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    @ch1234 I can see why. They get more money for Homeline! This may be one of those deals where HD lowballs certain items while overcharges for most others. Might be worth either hitting up Lowe’s or Menards, or calling round to genuine electrical supplies... – Harper - Reinstate Monica Jul 15 at 23:31

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