Many electrical panels and subpanels emit substantially elevated magnetic fields. This problem arises because breaker and neutral bus bars are configured so that the neutral and hot wires are separated once fastened in place, causing magnetic fields as discussed earlier. Some electrical panels are configured with the neutral bus bar split to run alongside the breakers. To cancel the fields, the hot and neutral wires would be the same length and installed beside one another. We recommend that such reduced field configuration panels and wiring be specified as indicated below:
• Panels and subpanels shall be configured so that hot and neutral field cancellation is possible.
• The following panels and subpanels are acceptable: Siemens EQIII, standard load center electrical panels, and subpanels with split neutral.
• Hot and neutral wires from the same run are to be installed adjacent to one another.
• Hot and neutral wire lengths shall be equal.
A dielectric union is a plastic joint that acts as an insulator, preventing the passage of electricity between conductive materials. In a typical home, conductive gas and water lines come into contact with appliances in several places. For example, water lines feed into refrigerators with icemakers, and gas lines feed into motorized furnaces. Should a fault occur in the appliance, wayward electricity will be distributed through the piping unless a dielectric union is used to isolate the appliance from the utility pipes. “Electrified” piping is undesirable for the reasons listed below:
• Magnetic fields will radiate out from the pipes.
• Net current in gas lines is an explosion hazard.
• Pipes carrying net current can become an electrocution hazard.
• Electric current flowing through pipes causes electrolysis, which results in decomposition of the pipes.
As discussed in Division 2, it is important to choose a site that is free from elevated magnetic fields generated from overhead power lines. Magnetic fields caused by faulty wiring in a neighbor s home also can be transferred into your home through utility service lines. Because electricity will follow all available paths, metal plumbing, gas lines, cable TV lines, and
tion of a 14-cent electrical nut to separate the two neutral wires. The magnetic fields throughout the house dropped to 0.5 milligauss, considered to be an acceptable level.
Discussion
This case study illustrates a simple code violation that went unnoticed by the electrical inspector. If the inspector had used a gaussmeter, the error would have been easily detected before final closeout. Surprisingly, such testing is not common practice. Had the tenant not used a gauss — meter, the code violation might never have been revealed.
telephone lines can become pathways for uninvited net current. Consequently, taking simple precautions to prevent such an occurrence is prudent when site conditions allow. Although the National Electrical Code mandates grounding and bonding, it does not dictate the configuration of utilities entering residential structures. By grouping the entry points of all utilities and providing proper bonding, any net current traveling through public utility lines will be shunted back without ever entering the home. However, pathways of elevated magnetic fields may be created in your yard. These too can be blocked, but will require the expertise of a knowledgeable consultant.
If site conditions do not allow for the grouping of all utilities, then testing with a gaussmeter for unwanted fields with the house power turned off would be a prudent safety precaution, both during construction and periodically thereafter. If new magnetic fields are
