cable

[redpis]

To the OP, yes of course you can use solid core phone cable to extend your system, you will encounter problems if you overtighten the connection or repeatedly remove and reconnect as it will fracture.

BS4737 allowed the use of soild core cable (lace wiring and tube & baton for example) and these are terminated at a junction box as they are static, 7/0.20mm alarm cable is used from there on (or after a door loop), the standard makes refernace to minimising false alarms, I presume this to be 'a single point of failure' with regard to the wire consisting of 1 conductor, rather that 7strands of 0.20mm.

The 7/0.20 definatly lets you make and remake the same connection a far more number of times than that allowed by single score cable before failure by fatigue.

 

[rk696]

That's a good point about terminations cold welding, and about stranded cable deforming under pressure. Makes sense.

And to the guy who said "It was a nightmare to work out what was what" when working on an alarm system wired in telephone cable. Why was that exactly? Because the colours were wrong? Surely you should work on the side of caution when working on a system, even one with kosher alarm cable, and bell out the conductors first anyway? You can't just assume that the colour code has been adhered to can you? You never know what muppet has been messing around with the system.

Shouldn't really take you any longer if you do the job properly in the first place..

 

[Paul_C]

For the reason Bernard has already mentioned - Solid provides a much better connection with a wrap-around screw terminal.

No it does not.

Why do you think that? It was the norm for many thousands of telephone connections before IDC started to replace screw terminals, in use for decades and considered perfectly acceptable - Including for all those old Post Office-provided alarm circuits.

You can't just assume that the colour code has been adhered to can you?

Well, even if you were trying to assume that, the first thing you'd have to guess at is which color code, as there is no single, exclusively used, code.

Red & black for power, blue & yellow for loop, white & green for tamper might well be one of the commonly used arrangements in Britain, but it's far from being the only one (not to mention the wiring to the outside box). And what about those proprietary units (remote controllers etc.) which don't all have the same specific terminals anyway?

 

[Alarm]

Why do you think that? It was the norm for many thousands of telephone connections before IDC started to replace screw terminals, in use for decades and considered perfectly acceptable - Including for all those old Post Office-provided alarm circuits.

Well chasing faults on items subject to vibration for starters.
Not many IDC joints move or get slammed do they!

Get correctly wound when terminating.

Got a few more reasons too,but as no one has answered the other question I`ll wait with them.

 

[bernardgreen]

Well chasing faults on items subject to vibration for starters.
Not many IDC joints move or get slammed do they!

True. but in situations where there is vibration then clamping of the cable will reduce or eliminate vibration of conductor relative to the terminal.

Vibration will damage a stranded conductor. The difference is they fail stand by strand until there are not enough strands to carry the load current.

Get correctly wound when terminating.

Correct installation is necessary for both solid and stranded.

Interesting that the stranded neutral leads on RCBOs are supplied with the ends cold welded into a solid square cross section for insertion into the neutral bar. Likewise stranded flexes are often ferruled when manufacturer fits a removable 13 amp plug.

 

[Mrdjc]

Is it just me or do these cryptic "I know the answer to what you are asking, but I am not sharing it until you tell me your answer" type of posts get on your nerves?

I'd love to know the reasons between cable selection for Alarms.

Telephone vs Alarm
Stranded vs Solid
Cross-sectional area's.
Interference.
Termination methods.

Etc etc.

 

[Paul_C]

Well chasing faults on items subject to vibration for starters.

Not sure what you mean - What sort of vibration are we talking about on items which are solidly attached to the fabric of the building?

Not many IDC joints move or get slammed do they!

How many screw-terminal joints of the type we're talking about do?

 

[Alarm]

Doors being slammed.
Windows the same to a degree.

You never seen contacts become intermittent? Or shocks?
Especially some of the newer stuff with junction boxes.