Knob and Tube Wiring

Most insurance companies and mortgage lenders consider knob and tube wiring, and/or a 60 amp service, to be unsafe or a high risk.

When initial 60 amp service was installed, only 6 to 8 distribution fuse panels were used and with today’s demands with additional appliances, this is not sufficient. The potential home owner may not be able to obtain a mortgage for a house until the electrical upgrades have taken place. This may prove to be an inconvenience and/or a major financial setback for those with a preset budget.

Before 1950, knob and tube wiring was designed so that the black and white wires can run separately. Today’s wiring system would have a single plastic sheathing covering both wires as well as a grounding wire. When installing knob and tube wiring, ceramic tubes were placed in drilled holes for the wires to run through for protection of wear against the wood. Another difference is the securing of the electrical wire. Knob and tube used elaborate ceramic knobs to clamp the wire to the structure, compared to today where the wires are stapled to the joists.

The connection for knob and tube was visible and the term “pig tail” developed from wrapping the wire around the ceramic knob and being soldered together to make a connection. Today, the connections are required to be enclosed in an electrical junction box.

Wiring for today’s standards is #14 gauge copper wire and is capable of handling up to 15 amps. Knob and tube is typically #12 and can handle up to 20 amps. The problems arise when connecting different wire gauges.

When adding additional outlets to the distribution fuses, people will use a higher amp fuse than allowable. This may cause the wires to overheat and the wire wrap to become brittle. Knob and tube wiring did not have a ground conductor. A ground conductor between 1950 – 1960 became standard. The concern comes from the changes made to the wiring of knob and tube and not the original installation, which would otherwise provide many more years of service.

60  amp services

An electrical service of 60 amps is usually found in older homes and they do not have as many distribution circuits as new panels. The risk associated with having a 60 amp service comes from the handyman making alterations or additions to the service. A 60 amp service is equipped with a 60 amp main fuse or breaker. If more electricity is drawn through the system, the fuse will blow or the breaker will trip. This is an inconvenience, but not an unsafe situation.

Although many insurance companies are reluctant to insure a home with knob and tube or 60 amp service, a well informed insurance agent may find a way to come to an agreement. With insurance companies working with the statistics on older wiring in houses, the numbers show that they do create a higher risk. But, not all houses can be treated equally, as the risk should depend on the overall modifications done to the home.

UNDERSTANDING THE ELECTRICAL SYSTEM

A home’s electrical system often originates at the main service panel. It then is divided into branches, called circuits, and connected by wires to wall outlets, appliances and switches throughout the house. Conductors, like copper and aluminum, are what carry electricity. Materials that are not good conductors of electricity are glass, rubber, plastic, ceramic, wood and paper, but are considered insulators.

In order for an electrical system to be safe, it must be properly installed or repaired according to a “Building Code”. As new materials and devices are known, the code is then updated to ensure the latest safety standards.

To determine the service voltage, count the number of wires connected to the service entrance. This carries the current from the service drop to the electrical equipment. Two wires designates a 120 volt service and three wires indicate available both 120 volt and a 240 volt service. Most small appliances and lights operate on 120 volts but heavy duty electrical appliances such as ovens, heat pumps, and clothes dryers require 240 volts. The amperage is determined by the size and the type of service entrance cable.

The electrical meter measures the usage of electricity in units called watts. These are equivalent to the number of volts times the number of amps. The hydro company then charges you for the amount of units used according to the meter readings.

The main service panel is usually located on a wall close to the central command post of your electrical system. Power flows to the outlets throughout the house from this panel. Some electrical systems have a single switch, lever or handle called the main disconnect which can shut off all the power in the house. Others may have up to six disconnects to shut off all the power. A single disconnect will usually be located very close to the electric meter whereas multiple disconnects are always located on the panel. It is important to know the type, number, location and operation of the main disconnect(s) in the event of an emergency or for any electrical work that is being done.

Every electrical system must be grounded so that in case of a faulty appliance, worn insulation or a voltage surge caused by a lightning strike, the electricity will be discharged into the earth instead of into the house or a person. System grounding is connecting the neutral wires from all the electrical circuits to a metal strip in the main service panel called the neutral bus bar. This in turn is connected by wire to a rod driven into the earth, or a metal cold water supply which goes into the earth.