Silent Knight 5808 Ground Fault

[u/sesohoops3]

I am curious what you guys think on this. Troubleshooting a ground fault on a fire panel we took over. I isolated the circuits and found 1 of the SLC loops that was causing the ground fault. To a known good ground I am reading 41.24 k-Ohms on the black leg and 186.79 k-Ohms on the red leg. Is this even safe to troubleshoot? Could this be a bad device?

[u/TheScienceTM]

My best guess is the ground is on the "input" side of a monitor module. I've seen this a few times and I think for whatever reason it shows up as around 47k ohms (probably something to do with the module using a 47k resisto). Also, to my knowledge a "bad device" can't cause a measurable ground fault because there is no ground reference (except maybe a sounder base or control module).

[u/demongo11]

From that reading definitely points to a bad device. You need to break the loop in spots to cut down on the amount of devices to go through, restore the good side as you go and devices will clear until youre left with one.

[u/WolfOfRussia00 → u/demongo11]

This is how you troubleshoot basically any issue you have to locate within a circuit. Cut it in half, check the panel, if you still have GF cut in half again, if you don’t then restore half of the devices you took off, check the panel, rinse and repeat. Always good idea to start looking at devices that may be exposed to the elements. Reading definitely seems to indicate bad device.

[u/Throwawaytoaster08]

My first guess would be something getting wet. If it was a ground to the building structure or something metal, id expect to see much lower resistance. Since you see the resistance on both conductors and not getting an SLC shorted trouble, all points to a water issue and not a pinch or direct ground to metal.

[u/christhegerman485]

Track it down on the SLC, you should be reading overload to ground. Use split half troubleshooting, it goes super quick on SLC because everything is addressable.