Play with some 'real' kit on my kitchen table.

[a_dad]

I now have 8 of Q20s and 100m shielded 8 core. I have one cable in.

[sixwheeledbeast]

Shielded is unnecessary for Texecom, as long as it's Cable Type 2 or above that's fine.

[a_dad]

Oh thanks.  I picked it since some legs will run past/near/briefly alongside mains cable.  

 

Reading about, I am getting location is key to minimising false positives.  It can be tricky, however, to find a corner that is not pointing at windows, not pointing at hot things (stoves/ kettles) and not directly over radiators.  My Rads are now heat pump rads, so seldom get to 48, usually upper limit is 40. Which is worse, over a rad, pointing at a rad, pointing at a window, or pointing at a stove/kettle? My front windows overlook my lightly trafficked road, if passing cars are an issue.  My rads really are pretty luke-warm when on. (They are pretty good at heating, though, since they are giant and have a high water flow rate).  

[sixwheeledbeast]

This is were experience from people that fit and design stuff is worth it's weight for letting them do it.

There is rarely a truly perfect corner so things have to be balanced. There are other things too, like accessibility to both work/maintain it and initially install the cabling. If the sensor maybe blocked in the future by tall furniture or curtains.

Passive IR will not penetrate surfaces so cars are no problem. Definitely not above a heat source. The stove/kettle most likely off if going out, unless you have an Aga type setup.

[sixwheeledbeast]

BTW "Type 2 or above" should really be clarified as Type 2 or better, i.e. PVC Type 2 or LSZH Type 1.

[james.wilson]

I'd say no rad can heat up quick enough I wouldn't worry about it say it. Above yes is an issue. The only force that can defeat the 1.6-2.4 degree a second change is our Sun. Apart from open fires and log burners. Tldr don't worry about radiators 

[PeterJames]

Dont worry about close mains, so long as you're not running in the same containment crossing paths is fine. So no real need for screened but if you use it only ground it one end. Rads cookers stuff like that wont heat up quick enough. Quad element with white light lenses is unlikely to trigger a fa from headlights from windows.  Open fires log burners will cause false alarms. Some furniture such as glass coffee tables will heat up quick enough on hot sunny days and can cause false alarms. It depends on which way the room faces etc. Animals will cause fa's unless you use pet friendly detectors, But Im just repeating what everyone else is saying. To be fair though false alarms are rare nowadays though the detector technology is so much better than it was 10 or even 5 years ago.