Which 4 core cable?

[fleetz]

Wondering what 4 core cable you guys typically use for PIR installs. 7x 0.20 or 14 x 0.20.

I realise the difference and typically use 14 x 0.20 as it is a no brainer as you do not need to think about cable lengths. Nearly all installs the max run is 25 metre (75 foot) more typically most are are a lot less than that.

Interested in what you are using in your installs?

Regards,

Fleetz

 

[Del91574]

Since the metric system never took off here
 
22 AWG.

 

[FlyingDiver]

This is the typical wire for PIRs in the US:  http://www.homesecuritystore.com/p-1196-win-w4-500-500ft-224-solid-burglar-alarm-wire.aspx
 
Fire and Smoke detector wire is a little heavier, and fire rated:  http://www.homesecuritystore.com/p-1131-fpl1121-2xu05-184-solid-fplr-500ft-red-wire.aspx

 

[fleetz]

Thanks guys...Wiki indicated that 22AWG is equivalent to 7 x 0.25 so close enough to probably switch to the 7 x 0.20 and where runs are 25m (75 ft) and over revert to the 14 strand cable. Certainly easier to fit off when you have a 15+ PIR install and a tight housing.

Be interested in finding out what you guys see as a comfortable cable run length on your 22AWG gauge wire for PIR's?

Without giving my age away I remember inches, pounds etc before here in Australia we went metric in I believe 1966 (don't get your calculators out!) gotta say if I had to work in fractions of an inch now my brain would turn to mush! (-:

Thanks for your input to date.

Regards,

Ian

 

[RAL]

A PIR detector draws only a modest amount of current.  Say 30 mA or so, depending on the particular detector you are using.
 
22 AWG wire has a resistance of about 53 ohms per km.   For a 25m wire length, you would see a voltage drop of about 0.08V if you are powering just one detector.    If you have one PIR per cable, you could go much further than 25m before you would need to use a heavier gauge wire.

 

[fleetz]

Thanks....I have a (100M (300ft) drum od 7x 0.20 which I am going to connect to a PIR and do some voltage and current measurements on.


Will feedback my findings.

Regards,

Ian

 

[Del91574]

A 75m run is trivial voltage drop per home run, same with overall circular mils and factor on circuit resistance....
 
I've hardly met a run outside of a very distant run (in hundreds of feet) where upsizing the cable AWG is necessary for practical reasons.