Don’t Reset The Main

Apologies for the lack of updates this weekend.  I’ve had my hands full with personal matters.  Among other problems, my house almost burned down Thursday afternoon:

This is a melted circuit breaker.  Specifically, it’s the 15-amp breaker from my central air.  The previous owner of my house installed the compressor himself, and used a 15-amp breaker where a 20-amp breaker was called for.  My adventures in discovering this and getting it repaired explain why you never, ever reset your main breaker without calling an electrician.

This all started Thursday afternoon.  I arrived home from work, disarmed the burglar alarm, and was greeted by my security system’s digitized voice:  “Disarmed.  Ready to arm.  Check system for trouble.”  I hit my status key and was told, among other things, “AC failure”.  I logged on to NextAlarm and saw that my power had gone off this afternoon at 1:29.  Knowing that the food in the fridge was still safe, I pulled out some formerly-frozen ground beef that had been thawing overnight and went to grill some burgers.  Up until this point, I had assumed that this was just another Met-Ed line failure (an all-too-frequent occurrence in my neck of the woods).

nextalarm

When I stepped out onto my deck, I noticed my neighbor’s TV blaring.  The juice was still on.

I went back inside with a sinking feeling.  As I approached my breaker panel, there was a strong smell of ozone and hot plastic.  Not good.  Something was seriously wrong.

I grabbed a shop towel (in case the panel itself had somehow become energized, because apparently some major, unknown failure was already in progress) and opened the breaker panel.  The smell got stronger, but I didn’t see or hear anything unusual — except for the fact that my main 200-amp breaker had tripped.

Everyone has experienced a tripped breaker on a branch circuit before.  It’s usually no big deal.  If you reset it and it doesn’t happen again, you pretty much forget about it.  But a tripped main is a different story entirely.  A tripped main indicates that something attempted to pull more than 200 amps of current through your home.  200 amps is, without qualification, a massive load of power.  Your main breaker should never, ever trip.  Even if one of the branch circuits shorts out, it should only trip that branch’s breaker (usually 15 or 20 amps).  To cause your main to malfunction requires some serious failure, like this:

I called an electrician to come check things out (because I know better, and because my neighbor’s main tripped once).  Upon arrival the next morning he immediately commented on the same ozone smell.  He popped open the panel and began removing breakers one by one.  The first breaker was for my air conditioning (the breaker you saw at the top of this post).  We immediately found the problem.

It turns out that the previous owner of the house had apparently installed the air conditioning on his own.  And although he properly wired the circuit with 12-gauge wire, he only used a 15-amp circuit breaker (the AC calls for 20).  After about 15 years of cooking at or just over capacity, the thing slowly melted into an inevitable failure.  I foolishly ignored the early warning signs — repeated trips of the same breaker — and ended up with what you see above.

Note the scorch marks.

See that stump between the two arrows?  That’s supposed to be a metal fork, just like the ones next to it.  All that’s left is a blackened metal stump and signs of arcing.  What likely happened is that the circuit overloaded, and the time-battered, under-rated circuit breaker failed.  Ironically, the circuit itself — being designed to handle the load — was fine, but the breaker — being designed to only handle 75% of the load — failed in spectacular fashion.  It appears to have melted and/or shorted out the two buses (the metal legs running down the length of a circuit breaker).

In the end, though, the breaker panel as a whole did not fail.  In fact, it performed exactly the way it was designed to.  When the short-circuit happened, the main breaker opened up, immediately cutting power to the system.  And the sealed metal box kept the sparks from spreading to the surrounding wood, drywall, insulation, or living space.  To be fair, the original circuit breaker performed its job as best it could.  It only failed because 15 years ago, someone made a terrible decision.

I picked up a new Eaton Cutler-Hammer panel and some replacement circuit breakers from Lowes.  Total cost for labor and materials was $550.  Although money is tight, what with us state employees not being paid right now, $550 is not a bad price for an emergency call, and is a steal against the expense of losing everything.

And besides, the guy who originally did this job in the early 90s probably saved a whopping two or three bucks by using an undersized breaker.  I hope I get a chance to meet him someday.

http://floor9.files.wordpress.com/2009/08/nextalarm.jpgpanel6f.jpg

7 thoughts on “Don’t Reset The Main”

  1. Dude, I’m not so sure about this. I’ve had the same thing happen to me as well although there was the correct size breaker in the box. Who was the manufacturer of the breaker that burned? Mine was Thomas and Betts.

  2. Thanks Robin. Luck indeed — I found a hole about the size of an eraser tip in the linoleum in the utility room floor. Not sure if it was a stray spark or not, but since my home is still here, I’m not asking any questions.

    @CobraMan, the old box was Siemens and the new box is Cutler Hammer. My first thought was that I might have had a FPE or Zinsco, but fortunately that was not the case.

  3. Thank you for posting this. I went away this week for a camping trip but was happy to find this when I came back.

  4. This is that good old aluminum buss crapp im a licenced electrician I use SQUARE D QO OR CUTTLER HAMMER CH OR SIEMENS WITH COPPER BUSS I see a lot of this type of fialure the guy didnt caus this ALUMINUM BUSSED panels are inferior I wont use them.

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