Owning a real estate brokerage and an electrical contracting company has a number of advantages for me. It's not unusual for me to offer electrical services to a client as a thank you for buying a home through our company. We just did that for a broken water heater. It can save the client a lot of money, and it endears them to both of our companies for the extra-mile service.
There is one issue that we run into a couple times a year that everyone needs to be aware of because it is terribly dangerous. Normally about the time it turns cold or the time it turns hot clients start having trouble with receptacles. It happens when they plug a space heater or an air conditioner into an outlet.
It works for a while, but then it stops working and normally knocks out whatever is down the line. The culprit more often than not is what is called backstabbing. A receptacle that is backstabbed or back wired is one where the electrician stuck the wires that feed the device into little holes on the back of the receptacle. It is perfectly legal and has been since the 70s, and it is probably one of the most dangerous "legal" wiring techniques you can employ in your house.
Devices should always have the feed wires wrapped around the screws in a fish hook fashion. The screws are then tightened down and the connection is solid. The backstabbed connections expand and contract with high energy appliances like heaters and air conditioners. When they do that, they begin to break connection and heat up. The heat ultimately melts the insulation off the wires causing a fire hazard.
This past year we inspected one house where the lady lost a line of receptacles, but the breaker stayed on. When we inspected her devices we found one that not only was a backstabbed receptacle the culprit, but it had charred the 2X4 it was mounted to and had melted about 30% of the box it was installed in. She was nearing a potentially tragic fire. I'm glad it stopped working long enough for her to call us.
If you want to check your devices you can do it simply enough. Turn off the breaker to a circuit. Take the cover place off and unscrew the receptacle mounting screws and pull it out of the wall. If the wires are plugged into the back, they are backstabbed. If they are fastened around the screws, they are wired in the preferred way. Check a couple more devices to make sure they're consistent, and always make sure the power is off before sticking your hands in any electrical equipment.