Ground Fault: Your Fire Panel May Not Be Protected!

You must pay attention to trouble signals resulting from ground fault error messages.

Even though your fire panel is working under this condition it is subject to internal electronic failure-no fault of the equipment.

There are many reasons why fire alarm system wiring is monitored for ground fault. Here are a few points to consider.

Firstly, what is a ground fault? A ground fault signal is when a wire has made contact with another electrical circuit or ground affecting its normal operating voltage, resistance, current and communication wave forms.

This ground fault condition could result in external voltage linking itself to a protected circuit either fully or partially through low or high resistive pathways. This grounding can occur through metallic conduits, electrical boxes, or to the building’s metallic structure. Skinned wires can cause a direct short, while crushed pinched or water soaked wires can cause low or high impedance grounds. Normally both the positive and negative leads, or a metallic shield surrounding communication circuits are sensitive to ground fault conditions.

This is an unacceptable condition in a newly constructed fire alarm system. However, this is often found in existing or badly installed systems.

We are all in agreement that fire alarm protection and the need for notification is a 24/7 function. These systems must be 100% functional and ready to act without notice. This is why these systems monitor wiring for ground fault.

1. 1. Normally a signal ground fault does not disable the fire alarm circuit. However, a multi-ground fault condition can disable an alarm circuit or notification circuit. This could be limited to a single circuit, a zone or building wide. The results of multiple grounds vary.
   2. So, if an initiation circuit is grounded the ability to detect an alarm event may become inoperable.
   3. If a notification circuit is in ground fault the ability to send audible, visual or mechanical warning tones may be incapacitated.

Without a doubt, ground fault detection is important, and we want to pay attention and repair these conditions as soon as possible.

However, this is only part of the message. Ground fault and the time needed to repair ground fault leads to a system vulnerable to electrical damage. Equipment such as CPUs, Addressable Loop Boards (SLC), Microprocessor Power Supplies, Battery Chargers and Addressable Field Devices are susceptible to damage caused by external voltages or a voltage surge.

Realize that the event of the ground fault will not damage the equipment. It is the fact that while in ground fault the equipment is exposed to another electrical path subject to electrical noise, stray voltages or voltage surges. It is this electrical noise, stray voltage or surge that damage the fire alarm equipment.

Where do these voltages or signals come from?

1. 1. • The utility company changing a transformer
      • The utility company repairing service lines
      • A brown out and voltage system trying to regulate
      • A power surge, a day or night of storms with lightning
      • Electrical mechanical equipment shutting down and starting up
      • Careless contractors working on other systems (Elevators, HVAC, Sprinkler System, Fire Pump, Dampers)
      • 120VAC power touching a conduit or building structure, or another low voltage system grounding to same conduits or circuits

All these acts can damage the fire alarm system while the system sits in ground fault condition.

So, in short, fix the ground faults as soon as possible. Your fire alarm system may not be protected and can lead to costly equipment replacement work.