As an Electrical Contractor, daily, I am called on to visit a house and try and locate the rationale that you will find electrical problems or outages. I push what I refer to as a rolling source home stocked with over 10,000 residential electrical parts in my truck so that I’m ready to correct any problem immediately. Getting back to the title question, residential wiring is generally still safe after several years of service. But, there are lots of distinct kinds of residential wiring, based on the time of your home. A number of those very initial electrical systems in homes and apartments were called Knob & Tube cable. It worked well in the time it had been installed, pre 1920’s and into the 1930’s, but is no longer considered secure. Many insurance companies won’t insure a home that still utilizes knob & tube wiring.
Throughout the 1930’s, steel conduit became the standard process of residential wiring. The conduit started at the fuse box and traveled out of socket box to socket box, from wall socket to light socket to change socket. Cable has been pulled through the conduit to every desired location for switches, lights and receptacles. In my view, this is the best strategy ever imagined, even to this day. Throughout the 40,’s & 50’s, many homes were wired using a coil steel jacketed cable called BX. Within the coil steel coat proved either 2 or 3 conductors, or wires, typically aluminum or occasionally steel. Steel has been used often during WW2. Following the BX period of wiring arrived Romex.
Now’s Romex is a plastic jacketed cable comprising 2 or 3 conductors (wires) like BX. Romex and BX are extremely similar in that the outer coat is eliminated in which it enters the socket box so that the conductors could be spliced or connected to the change, light fixture, or receptacle from in the outlet box. Both the BX and the Romex were stapled by hammer into the joists & claws. BX was tough to strip. Romex was much simpler and quicker to strip. A sharp knife is my favorite tool, whereas BX demands a particular tool which cuts through the steel coat. Throughout the late 1940’s, there was Romex in life, but the outer covering was a fabric and oil based material. It shifted into different kinds of outer coverings before the early 1970’s when it became the standard plastic covering which we continue to use now.
The safest residential cable, in my estimation, is the kind that’s shielded best from animals, nails, and some other means of cutting to the cable. Knob & Tube is definitely not secure. Early Romex will shred at which stapled to studs and loft joists, resulting in the possibility for a shorted circuit (if a hot cable comes in contact with the cable or ground cord). A brief is supposed to go to the circuit breaker or blow the fuse. If the breaker doesn’t trip, the brief will last to get hot and will quickly start an electrical fire.