Electrical Wiring Considerations for Older Homes
The main concern for older homes and their electrical wiring systems is the safety of the occupants of the home and the dangers of fire. Depending on the age of the home, various wiring methods may have been utilized that do not meet todays standards.
These types of wiring systems can include “Tube and Knob”, which is a wiring system that has conductors separated by several inches mounted on insulators throughout attics, basements, and through walls. Most of this insulation has deteriorated to the point that these wires are exposed bare and can pose a danger to persons or animals such as pets that might be navigating through these spaces.
Another type of wiring system found in older homes is “Cloth Braid” cable. Most of these systems do not have a grounding conductor installed in them which makes surviving an electrocution highly unlikely. We find many of the “2 prong” receptacle outlets have been replaced by 3 prong, grounded receptacle outlets. This is a violation of NFPA 73, Standard for Electrical Inspections for Existing Dwellings, 4.10.7.2 and 4.10.7.3, which states that any non-grounded receptacles that are replaced by grounded receptacles must have GFCI (Ground Fault Circuit Interrupter) protection and have the correct polarization between the ungrounded (hot) and the neutral.
The last type of wiring system found in homes since the 60’s to the 80’s is Type NM which has a derated grounding conductor, and NM stands for non-metallic cable which is similar to what is used today. Today we use Type NM-B which has a grounding conductor sized the same as the hot and the neutral conductors. This allows for a more complete clearing of a fault and minimizes the chances for a fatal electrocution.
Any of these wiring systems are still allowed by code but must be removed if there are any renovations. Anytime we are involved in a remodel or total renovation, we will remove any of these types of wiring systems that we encounter and can access. The liability of keeping these wires and cables in a home is not worth the risk of death or fire. To help mitigate these dangers we recommend that GFCI (Ground Fault Circuit Interrupters) and AFCI (Arc Fault Circuit Interrupters) be installed, either receptacles or breakers. GFCI’s are a device intended for the protection of personnel and functions to de-energize a circuit within 3 cycles which would be less that 1/20th of a second. These are also required to be installed when a wiring system is not grounded. AFCI’s are devices intended to provide protection from the effects of arc faults by recognizing the characteristics unique to arcing and by functioning to de-energize the circuit when an arc is detected. Electrical wiring is the number 3 cause of fires in homes in the United States. And of the top 5 causes of fires in homes, is the only one that is not caused by human error. Old electrical wiring is a ticking time bomb, and no one knows when it will go off and cause a fire. AFCI’s will defuse that ticking time bomb and provide the inhabitants an added level of peace of mind. We replaced an electrical panel in a 21-year-old home and recommended installing AFCI breakers on all the circuits. When we started turning on the breakers, two of them would trip immediately. We traced one to a faulty light fixture in the kitchen and the other was in a bedroom that was rarely used. Whenever we pulled a small bed from against the wall, we found a charred spot on the bed spread and the outlet had started to melt from the years of arcing in an outlet that hadn’t been used in 20 years. That outlet had been consuming electricity and the standard breaker never tripped.