Download ADT490 TroubleShooting Shorts 2 Shorts With a Ohmmeter Two

ADT490 TroubleShooting
Shorts
Shorts
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With a Ohmmeter
Two types
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Loose wire -> Ohmmeter sees
‣ One side open
‣ One side short
Bridging -> Ohmmeter sees
‣ Short from both side
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Detection - Wire to Wire Short
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Detection - Wire to Wire Short
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False Alarm
Determined after detection devices eliminated
Panel can’t tell the difference
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Detection - Wire to Wire Short
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Was work done in the area
Worker drilled through raceway
Water leakage in the building
Insulation stripped from the wire when pulled into
the raceway
If know wire size, can estimate locations
18AWG -> 6.4Ω per 300 m
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Detection - Wire to Wire Short
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Calculations
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Circuit is two wires
Circuit 6.4 Ω, then Lw is 300 m and Lc is
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Circuit is 4Ω
Lc is
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Calculations - Need “As Builts”
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Loose Wire Short
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Supervisory - Wire to Wire Short
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Signal Circuit Shorts
Terminal Labels - > Trouble
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Boolean Searches for Shorts
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With a short, checking for voltage -no voltage gives
no information
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Boolean Searches for Shorts
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Boolean Searches for Shorts
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Remove positive lead from device
Voltage increase (may require panel reset)
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Reset may reactivate signals
If signals disabled -> MAKE SURE SIGNALS ENABLE
BEFORE YOU LEAVE
Measure voltage at the device (should increase)
Fault is on the EOL side of the Test Point
If short on panel side, voltage remains 0V
Using resistance measuring may give additional info
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