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Tip of the Week
It is not my Fault!
Who is at Fault?
Man or Machine!
In this case related to a fire panel ground fault, it could be both and both are a problem.
I will first explain what a ground fault is.
In short, pardon the pun, a ground fault is what happens when the fire control panel, sub modules, wiring or end device come into contact with earth or chassis ground. It can occur anywhere on the system and to the untrained it can be the most difficult to find, especially if its an intermittent occurrence. This usually occurs on supervised circuits, but are not limited to them. When a ground fault happens, the panel does not give any specifics on where it may be, so that is where the hunting begins. The only indication is the ground fault indicator will be lit on the panel or listed on the display, depending on which fire control system your using.
What are the potential causes of a ground fault?
There are several instances of how a ground fault is given. Lightning, wiring that has come loose from its terminals, panels or modules that are not securely fastened to the panel or enclosure and my personal favorite is moisture due to bad conduit or cable connections and junction boxes. The latter usually occurs after a weather system has passed and as mentioned above would most likely be the intermittent type.
All fire control panels are equipped with a ground fault disable. This will either be switch or jumper that when removed/activated will make the panel ground fault disappear, and to all outward appearances an individual will believe that the problem is fixed. This is not the case. The ground fault disable is simply a tool used when trying to trouble shoot the ground fault, it is not a fix.
How do you know if the ground fault disable is activated or not?
Well for a technician, the panel schematic shows the layout and location of this function. For example on the Pyrotronics System 3 CP-
If you do not have access to the schematic, I would use a jumper wire and while connected to chassis ground, touch the other end of the jumper to any one side of the Initiating Device Circuits (IDC) or Notification Appliance Circuit (NAC). If while doing this, the ground fault indicator activates, then the ground fault jumper/switch is in its normal operating condition, if not then the system is not in its normal operating
condition.
If your using an intelligent fire control panel, pick any of the available NAC circuits to verify normal system operation. Keep in mind that ground faults can also occur on the Signaling Line Circuit (SLC). Also on some intelligent panels, there may be a programmable time delay before a ground fault is displayed, it may not be instantaneous like conventional panels.
Ground faults are self resorting trouble conditions, meaning they do not latch like an alarm would.
So in a nut shell,
Is disabling the ground fault acceptable and considered normal operating condition? NO
Is disabling the ground fault legal, well according to NFPA codes? NO
Could disabling the ground fault function cause any system problems? Most definitely
How do I proceed with trouble shooting a ground fault?
Well that is a long and technical discussion for another time, besides my fingers are hurting from all this typing LOL
The above information is covered in the following Tec Trek class segments: Awareness Training (FG-
For more information regarding training schedules and course curriculum, please visit our Web Site at www.tectrek.org or Contact Todd Olivier at (337) 298-
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Email: todd@tectrek.org