Linking Alarm Detectors

[eyeofthebeholder]

Hi

Situation:

I have three windows separated by walls in my lounge which I want to put magnetic detectors on. I obviously do not want to run a seperate to each.

Can you also link a PIR and a magentic on the same cable?

Is it feasible, and also best practise to connect them in series?

 

[breezer]

you can put what you like on any cable.

However you should not do it.

a contact (be it on a window or door) requires a tamper cct.

a pir requires 6 wires (assuming its a non resistor based panel)

the biggest average cable you can get is an 8 core (12 core does exist but it costs more and is thicker so harder to hide)

6 for pir leaves 2 for contacts

you can use a global tamper (using the same tamper pair for the pir as contacts) but its not a good idea

contacts on windows never look good

in "year dot" all doors and windows were contacted since they had nothing else, but as you have a pir why contact the windows ?

oh and you NEVER put a pir in series with a contact (same cable if you must, but never on the same cct)

 

[eyeofthebeholder]

I just like going a bit OTT on things

Suppose you are right, if I have a PIR, I won't need the mags!

Also (rather than creating another thread), I have been looking through for a 6core wiring diagram. Is there a standard, or is it specific to the alarm you are using?

 

[breezer]

makes no differance. (so long as you stick to the same colours through out)

alarm company A will use one combinastion, alarm company B will use another.

Logic would suggest red and black for 12v, but i have seen green and white used, black and blue and once red and white

many years ago some neighbours i had built their own alarm, yes it had every window contacted, (just windows) each window was connected to the next by differnt colours, their thinking was it will fool the intruder, truth is intruders dont care since they dont often break into houses with alarms

 

[eyeofthebeholder]

Thanks for the info breezer!

 

[Anteaus]

PIRs normally use a closed pair to signal activation, so this can be connected in series with a magnetic contact. This is standard installer practice, where for example a PIR is fitted over a door with a contact.

You need six cores (three pairs) to the PIR (power, signal, tamper) and four to the contacts, which you could take from the PIR housing if that is a convenient place.

HST, in domestic premises the need for an antitamper pair is questionable - who is going to tamper with it? Obvioulsy required in a public place though.

The only 'bad practice' here would be if the PIR and contacts were in different zones, since this would lead to a confusing situation.

 

[lvsystems]

Anteaus sorry you are wrong. It is not standard installer practice to series contacts and PIR's in fact regulations advise against this. Installer's sometimes use same cable for a contact and PIR but at the panel end these are wired into seperate zones. Whilst not ideal this is perfectly acceptable. You should not have a magnetic contact and a PIR on the same zone period. As for the need for a tamper for each zone it serves a valuable purpose it tells you that all your wiring is intact and that all your sensors are functioning correctly.

 

[breezer]

have to agree with Ivysystems (but you could turn a "blind eye" to the tamper, but its not really a done thing, any professional installer caught doing it gets a failure on a nacoss inspection, consitantly do it , your out.

tamper cct is a requirement of bs 4737

 

[Space cat]

Despite the obvious choice of red and black for the 12 volt supply it makes more sense to look at the colours in your four and six core cables. Use whatever extra colours exist in the six core for power. That way you can be consistent right round the house, eg red-yellow for alarm, blue-black for tamper and green-white for power.

Breezer and lvsystems are right about keeping PIRs and contacts in separate zones. You might want to arm the contacts but not the PIRs so that you can wander around the house at night. Alternatively, in a heat wave you might prefer to arm only the PIRs at night and leave a window or two open. Also, PIRs have so much more to go wrong. If one of them fails you can bypass that zone and still have some protection. And, last but not least, it makes fault finding so much easier.

Plan your zones carefully. Perhaps you want to give someone access through a garage and utility room to the back garden. You can do that if the relevant doors are in a zone of their own.

As far as tamper loops are concerned, I agree that a domestic alarm system hardly needs one but the facility exists so why not use it.