I'm not an electrician, but I used to be "darn near." I used to install and mostly service HVAC/R. I've seen numerous wire nuts loose or falling off. HERE IS A STORY THAT EVEN NOW makes my hair stand up
Back in the 80's--early 90's a friend of my boss called, "no heat." They had just bought a big ol OLD 2-3 story with an added dug basement, poured decades after the house was built. They had bought the house and were doing a "live in remodel." I went over to see what and did not take me long to find out that THE WIRE NUT IN THE FURNACE SWITCHBOX for the NEUTRAL was loose, and caused the furnace to stop
I remade the connection and fired it up. IT WOULD NOT VENT. This had a VERY tall chimney with a floor level cleanout. I took off the vent connector and the trap from floor to vent connector WAS FULL OF SOOT and had built up and plugged the VENT!!!!
It is well known that in houses that have previously been coal, wood, or even oil, and after converted to gas , that the gas acts as a detergent and eventually sluffs the soot off in the chimney.
HERE IT COMES!!!!
The folks had just roughed in bedrooms in the basement and were PLANNING ON MOVING THE CHILDREN down there over the weekend!!!
No CO detector!!!
Old furnance had no vent spill switch!!! (We added one)--which would have shut down furnace if not venting
THE ONLY THING THAT SAVED THREE KIDS was a LOOSE WIRE NUT
