LiquidWatch Installation Manual
37
Troubleshooting
Noise Problems
If a LiquidWatch system does not have proper earth grounding of the panels and shielded wires,
electrical “noise” can cause intermittent alarms or toggling between normal and alarm states. This
section will describe the procedure to troubleshoot a system with several Remote Probe Modules (RPM-
8) connected by 15-conductor communication cables (see Figure 6).
Grounding to Metal Backplate
The four backplate mounting screws are assembled with external tooth lockwashers next to the
backplate. The lockwashers cut through the paint on the backplate to give a solid metal-to-metal
connection. Make sure the lockwashers are in place on all 4 screws. An ohmmeter should be used to
verify the resistance from the earth ground (upper right backplate mounting screw) to each of the other 3
mounting screws is 0 ohms (Refer to Figures 1 and 2).
Shielding Test Procedure
1. Verify that the grounding connections of the LiquidWatch panel, the shields of the probes, and
the shields of the communication cables are to a solid earth ground (see Figures 1,2,6,7 and 8).
2. Disconnect the communication cable(s) from terminal strip P2 on the probe Bank 1 card to all
additional RPM-8s.
3. Check the probes for Bank 1 following the Probe Test Procedure below.
4. Connect the communication cable from this selected bank to the next RPM-8 in the circuit.
Disconnect all communication cables from terminal strip P2 on the new RPM-8. Check the
communication cable following the Communication Cable Test Procedure below.
5. Reconnect the 15-conductor cable to terminal strip P2 on the new RPM-8. Make sure all
untested communication cable(s) are disconnected from the new RPM-8.
6. Check the probes on the selected RPM-8 following the Probe Test Procedure below.
7. Repeat steps 4-6 until all communication cables and RPM-8s have been added to the circuit and
tested, one at a time.
Note: If a LiquidWatch Surge Suppressor (LWSA) is installed, the LWSA is Bank 1 in the tests
above.
Probe Test Procedure
1. Check for noise on Probes 1 to 8 by running the noise test on all the connected probes (see end
of Section 5.3)
2. If each of the connected probes on probe bank 1 has stable readings (within +/- 5) then continue
with the next step in the Shielding Test Procedure as outlined above.
3. If not, disconnect all but one of the probes connected to the probe bank.
4. Run the noise test on the connected probe and check if it has stable readings (within +/- 5).
5. If it is stable, connect the next probe and go to step 4
6. If it is not stable, there are several possible causes:
a. The shield wire between the panel and the probe is open, most likely at a splice.
i. Temporarily connect the 2 probe leads to the shield in the panel.
ii. At the selected probe, check for continuity between one probe lead wire and the
shield wire. The resistance should be less than 30 ohms/1000 ft.
iii. Repeat the test with the 2
nd
probe lead wire and shield.
iv. Locate and repair any open circuits. Retest after repairs.
v. Reconnect the probe lead wires and shield correctly.
b. The shield wire is not grounded properly in the panel.
c. There is too much unshielded probe lead wire at a splice or terminal strip connection
point. Shorten the unshielded probe wire as much as possible.
7. Go to step 4 until all probes are tested and stable. Then return to Shielding Test Procedure.
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