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1.1.6 Positive/Negative Earth Ground Faults
Simplex 4100 Series Fire Panels have the ability to detect positive or negative Earth Ground Faults. An Earth
Ground Fault occurs when an electrical circuit has a low resistance path to ground. It is imperative that Earth
Ground Faults are located and repaired as multiple earth faults can disable communications meaning small or
large components of the Fire Detection System may not function correctly (i.e. multiple earth faults on a Mapnet
loop can disable the entire loop communications channel rendering it inoperative).
Possible Causes (Examples)
Water Damage – creates electrical pathways
Terminations touching metal contacts or metal structures
Mounting screws piercing cabling
Damaged Card in a Fire Panel
Incorrect wiring to modules
1.1.6.1 Earth Ground Fault Detecting and Locating
There are various ways to test and locate an earth ground fault. The methods utilised can vary between the
different 4100 Series Fire Panels.
Simplex 4100U – The Simplex 4100U series fire panel has the most advanced earth fault monitoring available to
the Simplex Fire Panel Range. The 4100U has the ability to self diagnose and locate the general locale of an
earth fault, enabling the saving of much time and effort during diagnosis. There are two main Earth Fault
Detection options available for selection in the menu options (accessed via the 4100U fascia), a „Location Search‟
and an „IDNet channel Search.‟
To run an Earth Fault Diagnostic, you will firstly need to login to the panel with a sufficient access level as shown
below;
Access Level: 3
Passcode: 333 (Or contact your local Simplex Branch)
This will then enable the „Diagnostics‟ menu option available for selection. Choose a „Location Search‟ or an
„IDNet channel Search‟ and the panel will begin automatically searching different circuits trying to locate the fault.
Once the diagnostic has completed its search, you should then have a finite area to focus your repairs. The IDNet
channel search can even tell you which section of the loop (i.e. between which isolators) the fault is located.
NOTE – It is possible for Earth Ground Faults to switch from Positive to Negative Earth Ground Faults (or Vice-
Versa), so when disconnecting circuits it is highly recommended that you remove BOTH the positive and negative
connections for efficient diagnosis.
If you find that all the bays have been checked, and the earth fault appears to be in the main CPU Bay, the Earth
fault will most likely be in either the integrated IDNet Loop card found on the power supply, OR more likely, on the
Auxiliary fuse distribution card. The loop card can be tested as per any other loop card. The Auxiliary fuse card
should be unmounted (remove 4 screws) & insulate the Fuse Card from the mounting studs with paper or cloth. If
the Earth fault disappears, then the fault lies in the fuse card, otherwise you will need to individually disconnect
each of the 24V power supplies from the Fuse Distribution Board in turn, narrowing the circuit with the Earth Fault.
If the Earth Fault still remains, the fault is in the PSU
For more information on the specifics of 4100U Earth Fault Diagnostics, please refer to the 4100U Installation
Manual (LT0350) that was supplied with the panel.
PLEASE NOTE – Intermittent Earth Faults can only be diagnosed whilst the fault is active.
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