Douglas Krantz - Technical Writer - Describing How It Works
Get the book Make It Work - Conventional Fire Alarms

What is a Ground Fault?

Ground Fault Progression of a wire tied to a threaded rod
Example of a bad installation not showing up as a ground fault until years after being installed. A wire strapped to a threaded rod will only show small marks from the threads after a few days. The insulation will be part way penetrated after months. The insulation will be penetrated all the way through by the threads after years of being compressed by the wire tie. This becomes a ground fault and the ground fault is hard to find if it's above what is now a hard ceiling.


By Douglas Krantz

With the exception of the ground fault circuitry inside the fire alarm control panel (FACP) itself, the wiring for fire alarm systems has no connection to ground. Any connection conducting electricity to ground is causing a ground fault condition.

Ground faults are common; they can and do occur in almost any kind of fire alarm system. For the technician, fixing a ground fault is easy; finding it in the first place is the headache. Sometimes even following the wire is difficult.

Causes

Ground faults are the result of:

Single Ground Fault

Just to be factual, there is no problem with a single ground fault on any fire alarm system. It's just that the technician answering the phone off-site can't tell if it's only a single ground fault, more than one ground fault, or, in the near future, if more ground faults are imminent that will partially impair the system, completely disable the system, or cause false alarms. The ground fault light on the panel just doesn't say.

When to Fix a Ground Fault

Sooner or later, a ground fault has to be fixed. Some technicians might put off troubleshooting until the next business day if there are no other trouble conditions on the panel. However, depending on what causes the ground fault, waiting may be questionable. If any other troubles show on the panel, the troubles, and the ground fault, need to be fixed right away.

Having serviced fire alarm systems for nearly 20, Douglas Krantz has compiled his knowledge of the causes of Ground Faults and how to reliably detect them into the book Make It Work - Hunting Ground Faults. The book shows the three types of ground fault, what equipment should be used with each type of ground fault, and how to locate those hard-to-find ground faults.
Douglas Krantz -- Fire Alarm Engineering Technician, Electronic Designer, Electronic Technician, Writer

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