DEOL Wiring for Alarm Help Please

[jralfs1]

Hi,

I have just wired up a new alarm system using double end of line wiring. The problem is when there are two PIRs on the same zone.

Each PIR works fine on its own but when you move from one room to another and an additional PIR picks you up but the previous is still open circuit as you were just in that room then the alarm goes into detector fault when it is not set.

I am assuming that I haven't got the wiring or resistors quite right. It is 4k7 alarm and 2k2 tamper, wired using 4 core cabling.

Thanks for any help.

J

[ARW]

You should only have one sensor per zone when using EOL. TBH IMHO you should only have one sensor per zone when not using EOL.

If you use more than one sensor per zone (it can be made to work) you have a less secure system than not using EOL.

[Andrew Gabriel]

DEOL is normally used with just one sensor per zone. You can use more than one, but you need an extra wire or two between the sensors (depending if they are NO or NC, and if one side of the sense can be commoned with the 0v supply, which is not good practice). There needs to be a single 4k7 resistor in the zone. You connect the alarm contacts in series (assuming NO for PIRs), and connect the single

4k7 resistor in parallel across both of them. This will still go wrong if both sensors tamper at the same instant, but that's unlikely (even if they are attacked, one will be slightly before the other, which will trigger the tamper function in the panel).