Why do I have two PIRs wired differently ?

[Paul N]

Dear All.
I replaced a Normally closed PIR some months ago and followed the same wiring pattern as the previous one - 5 wires: +ve, -ve. tamper, N & C and no problems.

I am seeking to replace a second PIR but when I have opened it the wiring configuration is different +ve, -ve and tamper are the same but the two wires for N & C have been tied together and placed into N leaving C empty.

Both PIRs are single items on their own separate zones and both lead back to my Scantronic 9800 control panel.

Can anyone tell me why they have been wired differently, and what effect wiring the new PIR to one in N and one in C would have.
Many thanks for taking the time to read and respond.
Warm regards,
Paul

 

[Brother Blue]

C is the common and N is the NC contact, so joining the two wires together is bypassing the switch in the PIR and rendering it non-functional.

 

[Paul N]

Thank you Brother Blue - what's crazy about this situation is the reason I'm replacing the PIR is because it gives an alarm fault every time I set the system !!! This only started 6 days ago, I've checked the voltage and that's ok, the tamper is fine and so I'm wondering whether its the PCB in the panel.
Rather than replacing it I'm going to omit the circuit from the alarm set and see if that assists - I'm beginning to think there REALLY was a reason someone by passed the sensor in the first place !!
Any more thoughts would be gratefully received.
Warm regards,
Paul

 

[mainline]

Thank you Brother Blue - what's crazy about this situation is the reason I'm replacing the PIR is because it gives an alarm fault every time I set the system !!! This only started 6 days ago, I've checked the voltage and that's ok, the tamper is fine and so I'm wondering whether its the PCB in the panel.
Rather than replacing it I'm going to omit the circuit from the alarm set and see if that assists - I'm beginning to think there REALLY was a reason someone by passed the sensor in the first place !!
Any more thoughts would be gratefully received.
Warm regards,
Paul

You could run the panel in test mode, with the pir disconnected from the panel zone, with a link at the panel to check if the zone is working.