How do I wire magnetic contacts, can I connect more than one on a zone ?

Magnetic contacts (switches) are connected to the zone inputs on the control panel with UL rated Class 2, 22/2 cable. Either stranded or solid conductor may be used. 22/4 cable is employed by some to provide extra conductors for future expansion or in the event of a broken wire.

If connecting a single contact, it is simply connected across the zone (Zn) and zone common (COM) terminals as shown in Figure 1 below. Note that on a Closed Loop the End of Line Resistor (EOLR) is connected at and in series with the contact if employed.

Figure 1

If connecting multiple contacts on a Closed Loop, all contacts should be connected in series and if using EOLR’s the resistor should be placed at the sensor, which is furthest away from the panel. Figure 2 shows multiple contacts with wiring “Home-run” to the panel where the series connections are made prior to connecting the zone to the panel. This wiring method is preferred as it facilitates troubleshooting and maintenance.

Figure 2

             

Below Figure 3 depicts an alternative wiring method which, while electrically equivalent, places the series connections in the field. If this method is employed, care should be taken that all splices will be accessible in the event that troubleshooting should become necessary.

Figure 3