ADT490 TroubleShooting Grounds

2 Prior to Troubleshooting ‣ Before starting to work on the FACP, what do you do? 2

3 How to Use Ground LED ‣ Can use LED as tool -> which circuit has a ground fault by systematically removing circuits until ground fault LED turns off. 3

4 Finding Grounded Circuits ‣ Removing a circuit with a ground results in “ground fault” indicator LED turning off. ‣ CAUTION: There may be more than circuits with ground. ‣ For this reason, DO NOT replace circuit when removed -> may itself have a ground. 4

5 8 Zone System ‣ Remove & carefully tag and removing each circuit. ‣ When we disconnect Zone 7, we get this: 5

6 Locating Actual Ground ‣ Check out the circuit arrangement on the floor 6

7 Locating Actual Ground ‣ Zone 7 is laid out as below: 7

8 Locating Actual Ground ‣ Straightened out it looks as below: 8

9 Locating Actual Ground ‣ Disconnect to Zone 7 EOL ‣ Now only one conductors has ground contact ‣ Go back to FACP and disconnect positive wire. ‣ Does the “Ground” LED turn off? ‣ If it does, then ground contact is on positive wire 9

10 Locating Ground (Alternate Method) ‣ Remove circuit from panel & measure positive conductor ‣ Resistance reading is value of conductor to ground + resistance value of raceway 10

11 Locating Ground (Alternate Method) ‣ Remove circuit from panel & measure negative conductor ‣ Resistance reading is read through EOL = value of conductor to EOL + value of conductor to Ground + resistance value through raceway 11

12 Locating Actual Ground ‣ Note Zone 7 Trouble LED -> indicating an open circuit. ‣ It is open -> EOL is totally disconnected ‣ Positive wire at the FACP. ‣ Note that ground on the Zone 7 Initiating circuit did not cause the Zone 7 Trouble Led to turn on 12

13 Locating Actual Ground ‣ Step 2 – Finding the Grounded point with Boolean Search. ‣ With 2 technicians (technician & helper) ‣ one person on to 7th floor and other at FACP. ‣ Re-connect positive wire to positive terminal of Zone 7. ‣ The Ground Fault indication returns. 13

14 Locating Ground (2 Techs) ‣ The technician to the 7th floor, selects mid-point on circuit and opens circuit by removing a device -> ‣ Zone 7 Trouble is in Trouble(open) and Ground Fault are on with the System Trouble. 14

15 Locating Ground (1 Tech) 15 ‣ Circuit disconnected from Panel

16 Locating Ground (1 Tech) 16 ‣ Ground is between the TP and Panel

17 Locating Ground (2 Techs) ‣ Next device removed as a Test Point is Hallway smoke detector -> 17

18 Locating Ground ‣ Next device removed is Hallway smoke detector -> ‣ According to panel technician, Ground Fault Led is off. ‣ Ground is between Hallway smoke detector and Fitness Room heat detector. 18

19 Locating Ground (1 Tech) ‣ Next device removed is Hallway smoke detector -> ‣ Ground between smoke detector & Fitness Room heat detector. 19

20 Locating Ground (1 Tech) ‣ Ground is toward the EOL 20

21 Locating Actual Ground ‣ Step 3 – Verifying contact to Ground ‣ Section of circuit looks like “straight line”. ‣ There is a ground contact somewhere along this section of circuit wiring. 21

22 Locating Actual Ground ‣ Grounding point could be between Test Point and Party Room detector, or from Party Room detector onward. ‣ In Party Room, disconnect circuit leaving detector. 22

23 Locating Actual Ground ‣ Now our DMM displays this: ‣ There is no longer a circuit between wire and pipe. 23

24 Locating Actual Ground ‣ To confirm location of grounding point, connect DMM on wire in Party Room and take another reference with respect to ground. 24

25 end of presentation