Ground Fault FAQ’s
1. I have a Ground fault on my display. Does this mean that I have a bad earth ground?
No. This means that something in your system has a path to earth ground. In fact you must have a good
earth ground to sense a system ground fault.
2. Can I assume that with the earth ground disconnected from terminal 30 that I cannot sense an earth ground?
In general, you must have a good earth ground to properly sense a ground fault. However, if you remove
the earth ground wire, your panel may still have a connection to earth ground through the cabinet and
conduit connected. You may notice that the mounting screws for the panel are on a trace that is connected
to the earth ground terminal. This is by design and allows the cabinet to be grounded through the panel.
3. What terminals can affect a ground fault?
Any wire connected to the control can cause ground fault except the auxiliary relay terminals (these are dry
contacts) Sources of problems include: keypad wires, polling loop, bell circuits, zone circuits, peripheral
devices, powered devices J-connectors, phone lines, PS-24, battery connections, transformer, auxiliary
power supplies, radio backup devices….
4. Can other boards or peripherals (Power supplies, LRR radios, etc) cause a ground fault?
Yes. Any device wired to the control panel can cause a ground fault.
5. Can induced voltage cause an earth ground fault?
Yes. Anything that affects the voltage potential between earth ground and the rest of the system would
cause the system to report an earth ground fault, even though there is not, in fact, a real earth ground fault.
In this case, the “false” earth ground message still alerts you to a system problem.
6. Can conduit (that is usually grounded) affect ground fault?
Conduit can provide another path to earth ground. As mentioned in note#2 above, the panel mounting
screws provide an electrical path between the earth ground terminal (30) and the panel cabinet. This would
allow an earth ground to be sensed through the conduit even with nothing connected to terminal 30. This is
not a bad thing.
Some peripheral devices (7835C for example) Use a common negative to their chassis. In this case, if the
cabinet is grounded or has conduit that is grounded, an earth ground fault would be sensed through the
other connections to the device.
7. Does grounding the metal can affect ground fault?
As noted above, the panel mounting screws provide an electrical path between the earth ground terminal
(30) and the panel cabinet. Grounding the cabinet should not cause any problems.
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