I'm planning to lay the cables for a burglar alarm in my apartment at the
moment, and probably fit one at a later date, because I've got all the
skirting boards taken up at the moment.
What I would like to know is: Do I need a separate cable to the control
panel for each sensor, or just each zone?
I will have a patio door/window with 3 openings, and wonder if I can wire
all 3 magnetic contacts with one cable?
I presume the cable to the bellbox is the same standard 6 core cable at
It is really up to you. Most cheap panels are about 8 zone units although
more zones are probably not much more costly.
I would happily combine the patio door sensors all into one zone.
6 core cable will be sufficient for all the wiring although you can do 2
zones down an 8 core or 4 zones down a 12 cores if that helps.
As far as combining other sensors the issue is whether any sensor
would need to be treatd differently for any reason whatsoever than any
other sensor (eg. exit route, part sent, chime etc. etc.).
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Basically, as the other guys have mentioned, its up to you. One
usefull thing about having each sensor on its own zone is that you can
tell which one has triggered the alarm. This can be very usefull if
you get a false alarm. The down side is that you can end up with lots
of zones and it could get a bit confusing.
I put reed switches on all of the external doors (downstairs) and
pir's in all of the downstairs rooms, and 1 on the upstairs hallway.
I 'full' set it when the house is empty (all sensors) and part set it
at night (excludes upstairs hallway). One option, rather than lost of
reed sensors on each window opening, is to have the whole room
protected by pir.
If you use pirs then dont forget to seal the cable entry point. I
didnt, and we were woken at 1am on Saturday because a spider had
crawled into the pir.
It is also useful to distinguish a false alarm. If you have enough
sensors, it is unlikely an intruder will trip only one, so multiple
sensors triggering is a better indication of a real detection.
However, they have to be separately identifiable to the panel for
this to be useful -- the panel can't tell two different sensors
triggering if they are connected on the same circuit.
Also, you can't (easily) use multiple sensors per circuit if your
alarm supports dual end-of-line resisters and you want to use that
feature. (This also enables you to combine tamper and trigger
functions into just two cable cores.)
Reed switches on windows (and to some extend doors) are most useful to
remind you that there's one open when you arm the system. I suspect they
are not of much less use at detecting someone coming in through the window.
or drill the cable hole so the cable sheath is a tight fit.
If you are planning at some stage to get your system monitored
by a receiving centre, I would advise you run an extra
cable to rooms that have most valuables - that's if its not too much
trouble to do. (normally people do this after they realise alarms
don't stop people from breaking in)
Police policy these days require more than one detector to activate
in a certain time window - normally 30 to 60 minutes - before they
will attend. You would need a control panel compliant to the latest
specs for this.
Run a wire to your phone point too. It would be
neater to do it now while you have the place in bits.
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