Ground & Arc Fault Circuits
By David M Haught, CHI

This is a reprint from the Herald Dispatch Jan,14 th 2006 edition.
Home "Health" & Safety Tips
Ground Fault Circuits

I have received quite a few questions about grounded circuits and ground fault circuit interrupters.

The normal home circuits have a hot leg, usually a dark color wire, black, blue, red (anything except green), a neutral leg, usually a white or light grey wire and in a grounded circuit, a green grounding wire. To better understand how it works imagine electrons running along the hot wire into the appliance providing energy then along the white wire back to the power companies pole where it is grounded.

Electricity runs along the wires trying to go back to the ground. Naturally the electricity will seek the shortest path with the least resistance to ground. When you come in contact with a live wire you become the white current carrying wire to the ground. The electric current runs through your body "short circuits" your heart and causing ventricular fibrillation and death.

The green ground wire is there to provide a second shorter path to ground, with less resistance, than the white wire provides. It also provides a constant path for the appliance, improving safety over a two wire ungrounded system.

Technology has provided us with GFCI (ground fault circuit interrupters) to break the circuit. GFCI's contain a small current transformer. The circuit conductors pass through the transformer creating equal magnetic fields that balance. If the circuits become different the transformer amplifies the difference, sends a signal to a solid-state control circuit that activates a trip mechanism to break the circuit.

At one fourth of a milliamp you can feel the current, at 8 milliamps death can occur if the duration is longer than 15% of the heart's cycle. At 10 milliamps you can't let go and respiratory paralysis can occur. At 30 milliamps you go into ventricular fibrillation and death. Remember we are talking about milli amps. The branch circuits in your home are 15 or 20 Amps.

When a home is inspected, the Certified Home Inspector should test all GFCI (ground fault circuit interrupter circuits) not only for correct polarity and they trip, but that they trip below 8 milliamps and within milliseconds, less than 15% of a heart's cycle. Having the advanced equipment to thoroughly and accurately test your circuits can save lives!