adt490 troubleshooting grounds. 2 prior to troubleshooting ‣ before starting to work on the facp,...
TRANSCRIPT
ADT490 TroubleShootingGrounds
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Prior to Troubleshooting
‣Before starting to work on the FACP, what do you do?
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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.
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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.
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8 Zone System‣ Remove & carefully tag and removing each circuit.
‣ When we disconnect Zone 7, we get this:
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Locating Actual Ground
‣ Check out the circuit arrangement on the floor
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Locating Actual Ground
‣ Zone 7 is laid out as below:
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Locating Actual Ground
‣ Straightened out it looks as below:
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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
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Locating Ground (Alternate Method)‣ Remove circuit from panel & measure positive conductor
‣ Resistance reading is value of conductor to ground + resistance value of raceway
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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
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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
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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.
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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.
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Locating Ground (1 Tech)
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‣ Circuit disconnected from Panel
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Locating Ground (1 Tech)
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‣ Ground is between the TP and Panel
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Locating Ground (2 Techs)‣ Next device removed as a Test Point is Hallway
smoke detector ->
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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.
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Locating Ground (1 Tech)‣ Next device removed is Hallway smoke detector ->
‣ Ground between smoke detector & Fitness Room heat detector.
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Locating Ground (1 Tech)‣ Ground is toward the EOL
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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.
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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.
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Locating Actual Ground
‣ Now our DMM displays this:
‣ There is no longer a circuit between wire and pipe.
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Locating Actual Ground
‣ To confirm location of grounding point, connect DMM on wire in Party Room and take another reference with respect to ground.
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endofpresentation