According to the This Old House website, modern household wiring is a plastic-sheathed, insulated three-wire cable. Vintage wiring is generally grandfathered into current code assuming it was installed correctly when the house was built, provided it is still safe. So, if you purchase a 30- or 50-year-old home, for example, you may or may not have to upgrade your existing wiring, depending on condition of the circuitry. Maintenance may be as simple as changing a few circuits or having your wiring inspected periodically. In some cases, however, you may have to ask an electrician to rewire your home.
Knob and Tube
If your house was built before 1950, you may have knob and tube wiring, says the Living with My Home website. Knob and tube wiring consists of ceramic knobs supporting individual wires as they run through the house, and ceramic tubes protecting the wire where it runs through wall studs or floor supports. You may have to ask an electrician to upgrade your wiring if you're buying a home and need homeowner's insurance. Potential dangers with knob and tube wiring include temperatures that are too high for the circuitry to handle, such as the high temperatures found in ceiling lights, and unsafe wire splicing. A previous owner may have already done a partial upgrade. If so, you may only need the electrician to replace existing circuits and add new ones if, for example, you only have one electrical socket in a particular room. Today's code calls for electrical sockets within six feet of any point along any wall. To accommodate the extra circuitry, you'll also need to upgrade the breaker panel.
Armoured Cable Wiring
This is the next step up from knob and tube, says This Old House. Armored cable wires have flexible steel sheaths covering them, which are insulated with cloth-covered rubber. Sheaths must be anchored to a metal fuse box. This type of wiring works as long as the fuse box and insulation are in usable, safe condition. The biggest concern is making sure the amperage of the fuses are not higher than the wiring is able to handle. Once the insulation is damaged due to overheating, the circuit will need to be rewired.
Popular during the 1960s and 1970s, aluminium wiring was a copper substitute, but electricians no longer consider it safe, says This Old House. Aluminum wiring features a hot, neutral and ground wire wrapped in an aluminium casing. The problem is that overtime it can overheat and cause a fire, says Living With My Home. New aluminium alloy entered the scene in 1972, so if your home has this newer aluminium, the risk is not as great but still requires an electrician to make sure it's safe. Also, if your aluminium wiring is eight gauge or higher, like the wiring on your laundry appliances, you shouldn't have a problem. The best solution to this kind of wiring is asking an electrician to inspect it and upgrade as necessary. Be prepared, however, that renovations are time consuming and expensive, especially for a total rewire. Courses of action can involve crimping a copper wire to an existing aluminium wire, and then connecting the copper to the outlets, or connecting the aluminium and copper wire with connectors compatible with both.