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I have a question about something
Douglas Krantz -- Fire Alarm Engineering Technician, Electronic Designer, Electronic Technician, Writer




I have a Question

Mr. Krantz

Hello. I was researching a ground fault issue my client is having with his plant fire alarm system and a VFD installed in the plant. Would you happen to have any experience with this sort of failure or could you recommend any resources relevant to this type of problem.

The electrician is suggesting we disconnect the FACP ground and I am strongly against that solution.

Any help would be greatly appreciated.

Thank you.

M C

Ground Fault Light

On all fire alarm panels there is a separate ground fault light. It's a warning light.

Fire alarm systems are property protection and life-safety systems. If something goes wrong with a fire alarm system, a fire starting in the building could burn it down, and lives could be lost. It's not the annoyance of the ground fault light that you need to be concerned with; if the ground fault is not fixed, it's the possible dangers that you need to be concerned with.

Ground Fault Danger

A ground fault is an electrical leakage to the building ground - somewhere in the building. With fire alarm systems, a single ground fault (electricity leaking to building ground) usually isn't a problem. At this point though, the ground fault light on the panel comes on to warn you of danger.

The danger is that a second ground fault can occur. A second ground fault completes the electrical circuit between the ground faults and causes one or more possible problems:
  • False alarms
  • Failure to detect fire
  • Shorted power supplies
  • Fire horns going off when nothing is happening
  • Fire horns not going off when there is a fire
  • Etc.

If the first ground fault is not fixed, these are all possible problems with the life-safety system. Disconnecting the Fire Alarm Control Panel (FACP) ground doesn't fix the ground fault; disconnecting the FACP ground will only prevent the fire alarm panel from warning anyone of the ground fault danger.

I suggest you contact a fire alarm service company familiar with finding and correcting ground faults in fire alarm systems.

Annex 2 in the book "Make It Work - Conventional Fire Alarms" by Douglas Krantz shows how multiple ground faults in a building can cause false alarms and shut down power supplies.

Douglas Krantz

In the book "Make It Work - Conventional Fire Alarms" by Douglas Krantz, I'd like to show you how the fire alarm system works. The book describes the basic fire alarm system. Order Here

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How do I troubleshoot a ground fault? -- Troubleshooting a ground fault is like troubleshooting anything else. The first thing to do is stop and think. Ask yourself, what are you looking at? Read More

Can the Ground Fault Light be Used for Troubleshooting?-- A ground fault is an electrical leakage from the fire alarm system to building ground -- somewhere in the building. The ground fault light on... Read More

Why Do Ground Faults Keep Happening in Some Buildings? -- Someone on a condominium board wrote about recurring ground fault issues with his building. Some of the other board members... Read More

How Are Fire Alarm Loops Supervised to Make Sure They Continue to Work? -- Because the fire alarm system is a Life Safety System (people's lives depend on the fire alarm system working in an emergency), using supervision, the panel makes sure the field devices are always... Read More

Post this by your fire alarm panel -- It shows the in-house fire alarm system and how it calls the fire department.


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