This looks like a scenario our company avoided a few years ago, lucky us!
Addition to house, bed/office, and bathroom. Bathroom had all the little extras though, 2 heater/fan goodies, a couple of towel dryers, some nice big strip lights, a couple of cans all over the place, and the new central exhaust fan system for the skylight areas and close to the showers, we remodeled the other baths for some better venting.
OOOOOOPSIE, I forgot the laundry was added in the niche nearby, just a 20A 120V circuit.
House had an existing sub in before we arrived,main breaker a 150A, sub fed with a 100A. It did not appear that the panels were overloaded. They were about 20 years old. We had space in the sub to get our wires landed, AHJ was told to take a peek and see if he felt a full service upgrade was necessary to one new 200A service to avoid all doubt.
Well its about 5:30 when I show up with the last couple of light bulbs to finish, turn all the new goodies on for testing, all devices test fine, get back to the panel area and it starts to have a funny sort of plastic odor building up. Then we hear a little arc type noise from the main panel, hit the main breaker, pop the cover off both panels,take a look with a flashlight, can't quite tell where the meltdown is occuring. So, back on goes the main, a few seconds later we see smoke and a red glow happening under the main breaker, the meltdown is moving right through the bottom of main, all plastic in the area right for the back of the panel enclosure, the main has been off at this point again for a little bit, and it is still glowing quite well.
Now I have to do a beeline to the UG meter socket, not a disconnecting one either, basement back area of house, out the front door to the back corner of the house knowing this thing is still melting down until the meter is yanked. Hope she don't blow! Made it time to avoid iminent failure in a big way.
Anyone for a service swap at 6:30pm on a friday night?????????? Well the homeowner got a new 200A service installed by 1:00am.
So, all of that wind I used is to say that the main was in sad shape from the years of use, it didn't fail by just not holding, it decided to meltdown, and was going to take the panel and anything else in its path until the meter blew, or the TX.
We took amp readings to see if we could detect an issue of the first original panel and sub, all was within the breaker ratings.
And yes they had a spare Pampers for me!
