One of the most important "trouble" on any industrial or commercial fire alarm system is the dreaded "ground fault" trouble. If you have any experience in troubleshooting a fire alarm system, you know what I mean. Out of everything that could go wrong with a system, a ground fault is the most destructive of them all. Its because a ground fault can be a simple or impossible fix.
What is a ground fault?
A ground fault occurs when one or more electrical components on a fire alarm system is short circuited to a potential ground. This can occur when an exposed wire or device touches a metal "grounded" object. This could be a ceiling grid, junction box or just about any metal object attached to the building.
Normally, a fire system sends a trouble signal to the fire annunicator indicating a ground fault on the system. In this case, it is an actual grounded object or the ground jumper has been removed from the system. On some fire alarm systems, there is a jumper that can be removed to disable a ground fault trouble signal. If this jumper is removed, it is still necessary to restore the fire alarm panel to normal operation. Leaving a ground fault on a system hampers the systems normal function and violates the local fire code thus exposing the occupants to potential danger.
Why use the disable jumper?
Usually, the ground fault disable jumper is utilized to troubleshoot the fire panel by silencing the annunicator while repairs are being performed. It becomes a problem when the technician leaves the jumper on the system without repairing it. If for some reason the system can not be fixed at that time, a technician should sticker the panel with the violation and return to complete the service. At this time, the building management should be notified immediately to reduce liability.
What causes a ground fault?
In some instances, a ground fault can occur with a faulty installation that exposes wires to metal objects. It can also occur when being serviced or inspected during a scheduled interval. One of the most common reasons for a ground fault is lightning. When lightning occurs, electricity travels towards metal components thus shorting them out with an electrical surge. It most cases, this causes the fire alarm panel to become defective needing replacement. It is important to add surge protection and proper grounding procedures when installing.