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Fire Alarm -- Maintenance

Shiner on a wire coming out of a back-box that caused a ground fault
Photo Courtesy Integrated Fire & Security
This bare copper leaks electricity from the wire to the electrical box. It took years, but the insulation finally rubbed off, exposing the copper.
Douglas Krantz -- Fire Alarm Engineering Technician, Electronic Designer, Electronic Technician, Writer

Why Do Ground Faults Keep Happening in Some Buildings?

By Douglas Krantz

Someone on a condominium board wrote about recurring ground fault issues with his building.

Some of the other board members think that the fire alarm technician isn't really fixing the ground faults, rather the technician is conspiring with either the fire department or the condominium's management company to keep having to return, and get paid.

He thought that was absurd. He thought the technician who fixes the system, the one who walks away from the site with the fire alarm system normal, is the solution, not the problem.

It's the Original Installation

If the ground fault light keeps coming on, the real cause of multiple ground faults is bad wiring practices at the time of the original installation. It's the wires, through damaged insulation somewhere in the building, leaking their electricity to building ground.

Ground Fault Time Bombs

Taking months or even years to show up, ground faults are time bombs.
  • It takes time for sharp metal edges to rub through insulation
  • It takes time for insulation pinched between metal ductwork to get thin enough to conduct electricity
  • It takes time for a bare wire to sag enough to touch the side of an electrical box
  • It takes time for insulation pressed against a threaded rod to be penetrated by the threads
These issues get their start at the time of installation.

Hidden Wires in the Building

Leaking electricity to ground, each ground fault is at a separate point in the building.

The trouble is that the wiring, going to each detector or horn/strobe, is hidden. The panel may show a ground fault, but it can't say where. Therefore, even though the wires are hidden, it's up to the technician to follow these wires.

Hard to Find, Easy to Fix

Before fixing the damaged insulation on the wire, the technician has to first find the location.

Once the actual point of electrical leakage is found, however, this leakage can easily be fixed by:
  • Cutting off damaged wire or insulation
  • Repairing damaged insulation
  • Installing protective shields
  • Rearranging wire inside an electrical box
  • Hanging a wire in a different place
  • Etc.

Recurring Light on the Panel

Remember that the fire alarm system displays a ground fault at the panel, but the ground fault is somewhere else. Also, each ground fault is a separate problem to be repaired; fixing one ground fault doesn't fix the others.

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All Will Be Fixed

In in any building, there are a finite number of potential ground faults. Eventually, most of them are going to be repaired, and the number of ground faults will decrease to near zero.

Regarding Multiple Ground Faults in a Building

Many technicians can't visualize the whole fire alarm system well enough to follow hidden wires through a finished building. Having found a technician who can reliably find and fix the ground faults, the other board members of the condominium mentioned above should consider themselves lucky.


Douglas Krantz

Describing How It Works

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Electrical Flow

On this website, most references to electrical flow are to the movement of electrons.

Here, electron movement is generally used because it is the electrons that are actually moving. To explain the effects of magnetic forces, the movement of electrons is best.

Conventional current flow, positive charges that appear to be moving in the circuit, will be specified when it is used. The positive electrical forces are not actually moving -- as the electrons are coming and going on an atom, the electrical forces are just loosing or gaining strength. The forces appear to be moving from one atom to the next, but the percieved movement is actually just a result of electron movement. This perceived movement is traveling at a consistent speed, usually around two-thirds the speed of light. To explain the effects of electrostatic forces, the movement of positive charges (conventional current) is best.

See the explanation on which way electricity flows at