ADT490 TroubleShooting Locating Opens A

2 Introduction Breakdown in Circuit Integrity -> Trouble Metallic continuity interrupted an “ open ” occurs System Trouble LED is lit. Open on a conventional Initiating circuit Yellow Zone LED -> on

3 Introduction ‣ Open on signal circuit indicate ‣ circuit is Open ‣ “Circuit” or “NAC” yellow LED ‣ System Trouble ‣ LED ‣ Buzzer 3

4 Introduction ‣ Class B Initiating circuit : 4

5 Typical Input Circuit ‣ Continuous power ≅ 24 Vdc ‣ EOL Installed after last device ‣ Regulates current ≅ 5 to 6 mA ‣ Current called -> supervisory current ‣ Break -> current stops -> 0 mA ‣ Sketch – why no supervisory current ‣ Insert Multimeter (series) at FACP, set to mA -> 0.0 mA ‣ Insert Multimeter (parallel) at FACP, set to V -> 25 Vdc 5

6 Typical Input Circuit ‣ Break -> ome devices still operate ‣ If 1st device is a Manual Station Operated ‣ Places short on circuit prior to break (still powered) ‣ Causes Alarm Condition ‣ Remaining three devices electrically disconnected ‣ Cannot cause Alarm ‣ Devices panel side of break – function ‣ Device on EOL side of break - inoperable 6

7 Simple Exercise - 1 ‣ Example of using senses, logic and DMM to find an open circuit in a simple Class B circuit ‣ Imagine the circuit in Trouble is on Zone 2 on a 4 Zone FACP ‣ In this Apartment Building Zone 2 is the entire Second Floor 7

8 Simple Exercise - 2 8

9 Simple Exercise - 3 ‣ Wire disconnected somewhere on this circuit. ‣ “ Disconnected ” implies what type of a circuit fault? ____________________________ ‣ What will FACP to tell us? 1)_____________________________ 2)____________________________ 9

10 Simple Exercise - 4 Visit 2 nd floor. ‣ What will suggest where the open has occurred? 1)_______________________________________ 2)_______________________________________ 10

11 Simple Exercise - 5 The raceway layout might look like this: 11

12 Simple Exercise - 6 After a visual inspection ‣ open location not obvious (hanging device, damage caused by renovation or repair, etc.), and ‣ will probably require some meter work to locate it. ‣ Visual inspection suggests problem -> middle to end of circuit 12

13 Simple Exercise - 7 What clue(s)? Remember: “ Any device on the panel side of a break in a Class B circuit will continue to work, while any device after the break is inoperable ”. 1)____________________________________ 2)____________________________________ 13

14 Simple Exercise - 8 Inspection -> both hallway smokes flashing LEDs First Manual Station worked Last one did not. Let ’ s look at the circuit again: 14

15 Simple Exercise - 9 Open circuit has occurred between the last smoke detector and last Manual Station. we haven ’ t to access into any suites. 15

16 Simple Exercise - 10 ‣ Convenient test point is second smoke because: __________________________________and, because of the way the conduit is run, we can_______________________________ 16

17 Simple Exercise - 11 Remove the second smoke & Check with Meter 17

18 Simple Exercise - 12 Meter to conductors into octagon-box from the FACP. What should meter be set for? _______________________________ What reading is expected (app.)?______________________________ 18

19 Simple Exercise - 13 We got what we were looking for Look the other way down the circuit to the EOL. Locate other two wires removed from smoke detector. 19

20 Simple Exercise - 14 Do we leave the meter as previously set?________________ What setting is going to be helpful? ________________ If this part good (pretty sure it isn ’ t) What read should we expect? (app.)? _______ With circuit open between Test Point and the EOL What reading will you get? _____________________ 20

21 Simple Exercise - 15 Wiring looks like this: 21

22 Simple Exercise

23 Simple Exercise - 17 Open is between octagon box and the EOL. 23

24 Simple Exercise - 18 Resistance reading of 4.8 kΩ, seeing EOL. Open is not between the octagon box and the EOL. Open has seemingly between the heat detector in suite 203 or the heat detector in suite

25 Simple Exercise - 19 Remove remaining Marrettes and short together RED and BLACK going to Suite 204. Put your DMM (on resistance) across the returning blue and brown wires. If shorted (0 Ω) -> the wires intact & connected to the detector -> wires to Suite 204 OK 25

26 Simple Exercise

27 Simple Exercise - 21 Apply same routine and find there is an open -> DMM ’ s resistance is infinity. 27

28 Simple Exercise

29 Simple Exercise - 23 Access 203 Dismount the detector & Blue wire broken off detector ’ s terminal screw, -> causes open circuit. Re-strip & re-connect blue wire Remake the connections in the octagon box Re-mount the heat detector. Check to see that the FACP is clear. 29

30 Discussion How to troubleshoot an open on a Class A circuit? Typically a Class A looks like this: 30

31 Discussion 1) There are 4 wires associated with the Class A “ loop ”, 2 leaving the panel and 2 returning. 2) The EOL function is inside the FACP. 3) The circuit is actually working like a Class B loop, in the normal mode. 4) The arrows represent 2 “ switches ” that are “open state” 31

32 Discussion When open occurs relay causes switches to close Feeds the voltage to the other side of the open 32

33 Discussion An open/break occurred. 1) FACP senses drop in current on loop and closes the two “ switches ” (as indicated by the arrows). 2) Now we have +24VDC being supplied to the 4 th terminal, and the 0VDC reference being supplied to the 3 rd terminal. 3) The FACP is now back feeding the operating voltage and current to the devices beyond the break. 4) ALL DEVICES CONTINUE TO FUNCTION. 33

34 Discussion All devices work -> smoke detectors flash LED ’ s -> location of break more difficult to find 34

35 end of presentation