1. ADT490 TroubleShooting Locating Opens

2. 2 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

3. 3 Bonding ‣ Exterior raceway components bonder to Ground conductor ‣ reduces interference -> EMI, RFI, & ESI ‣ Easirer to test ground during VI 3

4. 4 Bonding 4

5. 5 Ground-to-Ground Short ‣ False Alarm 5

6. 6 Positive Ground ‣ Higher end panels - may show as Positive on LCD 6

7. 7 Ground Fault Processing ‣ Often within 1 second to 90 seconds ‣ Lower Priority than Alarms, & Supervisory conditions ‣ Return to normals even lower Priority 7

8. 8 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 8

9. 9 Finding Grounds in Large Panels ‣ Modules often have 8 circuits ‣ CPU Communicates with modules through cables 9

10. 10 Finding Grounds in Large Panels ‣ Boolean Search through cables ‣ De-energize panel remove cable ‣ Localize to one module ‣ Do small panel search when localized 10

11. 11 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” 11

12. 12 Diagnosing Ground Correctly 12

13. 13 Measuring Grounds on Positive 13

14. 14 Measuring Grounds on Negative 14

15. 15 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 15

16. 16 Measuring Grounds 16

17. 17 Causes of Grounds ‣ drilled through raceway ‣ insulation stripped during insulation ‣ wire loose to metal backbox or cover 17

18. 18 Locating Grounds on Class B Ccts 18 ‣ Boolean Search

19. 19 Locating Grounds on Class A Ccts ‣ Boolean Search 19

20. 20 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 20

21. 21 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 21

22. 22 Internal Grounds on Large Panels ‣ Boolean search through Card Communication Ribbons ‣ Can sometimes remove card -> Ground clears ‣ Replace cards or CPU as appropriate 22

23. 23 end of presentation