adt490 troubleshooting locating opens. 2 power supply grounding power supply has circuit ->...
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![Page 1: ADT490 TroubleShooting Locating Opens. 2 Power Supply Grounding Power Supply has circuit -> allows positive & negative outputs to float relative to ground](https://reader036.vdocuments.mx/reader036/viewer/2022062517/56649f155503460f94c2aae4/html5/thumbnails/1.jpg)
ADT490 TroubleShootingLocating Opens
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Power Supply Grounding
‣ Power Supply has circuit -> allows positive & negative outputs to float relative to ground
‣ Green AC input wire -> building Ground‣ Resistance to ground ≤ 10 kΩ
‣ results from abnormal operation‣ Originally, negative was ground
‣ System Fault -> Ground Fault‣ Non specific - one or many‣ Internal or External
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Bonding
‣ Exterior raceway components bonder to Ground conductor
‣ reduces interference -> EMI, RFI, & ESI
‣ Easirer to test ground during VI
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Bonding
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Ground-to-Ground Short
‣ False Alarm
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Positive Ground
‣ Higher end panels - may show as Positive on LCD
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Ground Fault Processing
‣ Often within 1 second to 90 seconds‣ Lower Priority than Alarms, & Supervisory conditions‣ Return to normals even lower Priority
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Finding Grounds in Small Panels‣ Remove field wiring & install EOLs
‣ Eliminates Panel itself‣ Field
‣ Remove EOL and install field wiring‣ Tag and remove
‣ Find All Circuits with Ground Faults
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Finding Grounds in Large Panels‣ Modules often have 8 circuits‣ CPU Communicates with modules through cables
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Finding Grounds in Large Panels‣ Boolean Search through cables
‣ De-energize panel remove cable
‣ Localize to one module‣ Do small panel search when localized
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Diagnosing Ground Correctly‣ Do not accept LCD info at face value‣ Ground can trigger at 50,000 Ω‣ On positive but can still be detected through
negative wire -> “pass through”
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Diagnosing Ground Correctly
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Measuring Grounds on Positive
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Measuring Grounds on Negative
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Measuring Grounds
‣ Most consistent method - A‣ Positive lead on panel chassis or ground lug‣ Negative Lead on system or circuit common‣ Always gives 0 to 30 V
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Measuring Grounds
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Causes of Grounds
‣ drilled through raceway‣ insulation stripped during insulation‣ wire loose to metal backbox or cover
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Locating Grounds on Class B Ccts
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‣ Boolean Search
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Locating Grounds on Class A Ccts‣ Boolean Search
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Boolean Searches for Grounds‣ Same approach as Opens and shorts‣ REMOVE BOTH WIRES
‣ Middle of circuit, remove both wires‣ If ground goes off -> toward EOL‣ f ground stays on -> toward Panel
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Internal Grounds on Small Panels‣ Remove field circuits with EOLs‣ Check Battery connectors‣ Foreign materials near chassis and mounting screws‣ Remove Circuit board -> closely inspect for foreign
materials ‣ If ground remains -> replace Circuit board
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Internal Grounds on Large Panels‣ Boolean search through Card Communication
Ribbons‣ Can sometimes remove card -> Ground clears‣ Replace cards or CPU as appropriate
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