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Guest rjenkins

Alarm installation - cable type query

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I once read a few years ago where a NACOSS company used twisted pair for ALL runs in ALL installations and it drastically reduced theyre FA rate.

Would be a pig to work with tho!

44788[/snapback]

They must have been piss-poor in the first place to have so many false alarms to start with :rolleyes:

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One of the other threads in this topic mentions cable types & it has me puzzled.

I don't follow the reasoning on this.

In any good twisted pair data cable, the two cores in each pair will be very closely matched in length.

The normal cable used for alarm systems is fairly cheap & nasty stuff, it's nothing like the quality of a generic industrial 7 x 0.2 multicore.

or is there just a minimum specification? ,

I was specifically planning to use screened twisted pair for linking the keypads to the main unit on my new installation, so I am very curious about this!

44684[/snapback]

Did we mention regs and cable last week Cable

Jef


Customers!

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Guest
Did we mention regs and cable last week Cable

Jef

44792[/snapback]

Quote from that post "Think about cable! Manufacturers recommend types of cable, Not BS, so no regs, does this mean wet string is OK! "

:roflmao:

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Specs for CQR alarm cable

Core Resistance: 92 OHMS/KM

Conductor Area: 0.22mm^2

Current Rating: 1 Amp

Core Gauge: 24 AWG

Insulation Thickness: 0.3mm

Sheathing: PVC Type 1

Maximum Operating Voltage: 50v RMS

Operating Temperature: 70 degrees centigrade

Rip Cord: Yes

Screen Material: N/A

BS4737 3.3.0


There are no stupid questions, but there are a LOT of inquisitive idiots.

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Guest
Thats for FLEXIBLE connections.

44776[/snapback]

You mean door loops etc etc etc?

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You mean door loops etc etc etc?
Yeah :)

........................................................

Dave Partridge (Romec Service Engineer)

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Guest

Makes sense now - so ive been thrown by a previous mis-quote, arrrrrr - thank you grasshopper, I am now enlightened.

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Guest
They must  have been piss-poor in the first place to have so many false alarms to start with  :rolleyes:

44791[/snapback]

I don't know what cable they used, but i neverever have got a FA due to cable (and if it wasn't clear by now.. I use CAT3 single stranded ( MHS 3/5/10/20 pair x 0,5+0,5 (where 0,5 is diameter) ) ). THOU i know many systems that FA due to voltage loss in the cable when mains voltage drops. This thou doesn't have anything to do with cable but the installer who didn't count the power loss.

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I don't know what cable they used, but i neverever have got a FA due to cable (and if it wasn't clear by now.. I use CAT3 single stranded ( MHS 3/5/10/20 pair x 0,5+0,5 (where 0,5 is diameter) ) ). THOU i know many systems that FA due to voltage loss in the cable when mains voltage drops. This thou doesn't have anything to do with cable but the installer who didn't count the power loss.

44803[/snapback]

My point exactly.

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Guest
My point exactly.

44804[/snapback]

For petes sake stop agreeing with me all the time!!! Before we used to have nice :boxing: , but now everyone (well, almost) agree with me.. :cry:

Or then even I have learned something every day...

:question:

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Guest
For petes sake stop agreeing with me all the time!!! Before we used to have nice  :boxing: , but now everyone (well, almost) agree with me.. :cry: 

Or then even I have learned something every day...

:question:

44808[/snapback]

-You learnt something? - dont push your luck!! :roflmao:

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Guest
-You learnt something? - dont push your luck!! :roflmao:

44811[/snapback]

:lol: :lol: :whistle:

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I've got to disagree here. Any CE marked equipment should have passed EMC compatibility tests, and many manufacturers exceed the CE requirements and quote the figures.

Look at any Texecom spec sheet and you will see an RF Immunity rating.

Their RF series PIRs are designed for nasty environments and have much higher immunity ratings.

44777[/snapback]

As i said i wasnt aware of any manufactures, i didnt say there wasnt any!

And if theyre kit is so good against rf why do they make a special rf immune sensors?

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Guest rjenkins

Oops, missed the 'flexible' bit, that does make sense.

(But I don't think generic door flexes actually bother complying - the ones here, installed in 98 according to the paperwork, have cores no bigger than the basic alarm cable - certainly not 0.5mm2. The last time I had reason to cut one, admittedly many years ago, the cores were actually 'tinsel' wire like old phone flexible cables - possibly 0.1mm2 ?)

Re. different RF immunity ratings, the basic stuff needs to be safe with 'environmental' RF like mobile phones, passing Taxis & PMR etc., where the high immunity stuff should still be OK near higher power installations like sites with transmitters.

I'm getting the impression that 'Alarm' cable does not appear in a class of it's own due to any critical requirements, but because the BS specs for cable are so minimal that cables manufactured to (just) meet the spec are not actually fit for much else...

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Guest

Where does that leave single core phone cable then....

The debate goes on, we have people coming on here asking if they can wire an alarm with phone cable.

For the cost of the alarm cable, I cant understand why you want to redesign something that aint broke - i.e. if it aint broke dont fix it.

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Where does that leave single core phone cable then....

The debate goes on, we have people coming on here asking if they can wire an alarm with phone cable.

For the cost of the alarm cable, I cant understand why you want to redesign something that aint broke - i.e. if it aint broke dont fix it.

44848[/snapback]

it leaves single strand CAT3 to coldshire then.. :lol:

ofcourse people CAN wire with whatever they find but if it is against reg's and common practise there it isn't quite a good idea.

I ordered 100m of UK alarm cable and found it to be good for DC-loop systems especially because that manufacturer had two thicker cores for pwering detectors etc..

i would be interested thou what is capasitance between cores in UK alarm cable.

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Guest
So can we use wet string?

                                    :roflmao:

44855[/snapback]

I have heard that UK is situated in a rainy island so why not??

:lol:

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Guest
I have heard that UK is situated in a rainy island so why not??

:lol:

44863[/snapback]

Georg - you are silly at times! - its because it has to be insulated wet string of course! :yes:

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Guest
Georg - you are silly at times! - its because it has to be insulated wet string of course!  :yes:

44867[/snapback]

maybe isolated as well..?

:question:

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Georg, I dont know what the capacitance is , but you probably know how to work it out.

The NVP of alarm cable is 57% where as Cat5 is 67%.

Thats all I know.

And to the original poster, just use normal 8 core 7/.22 alarm cable.


The opinions I express are mine and are usually correct!

(Except when I'm wrong)(which I'm not)

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Guest
Georg, I dont know what the capacitance is , but you probably know how to work it out.

The NVP of alarm cable is 57% where as Cat5 is 67%.

Thats all I know.

And to the original poster, just use normal 8 core 7/.22 alarm cable.

45006[/snapback]

NVP?

:question:

(Non Volatile Polarity ... :roflmao: )

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Look Here....

http://www.nordx.com/public/htmen/Tech_Tip_3.htm

Apparently Capacitance is directly proportionate to NVP but I dont know the formula.


The opinions I express are mine and are usually correct!

(Except when I'm wrong)(which I'm not)

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blic/htmen/Tech_Tip_3.htm[/url]

Apparently Capacitance is directly proportionate to NVP but I dont know the formula.

45049[/snapback]

From the web:-

Nominal Velocity of Propagation (NVP)

In a conductor, electrons travel at near the speed of light. For a copper cable this speed is often expressed as a decimal fraction of the speed of light. (UTP has an NVP of about 0.59-0.65).. The lower the NVP, the greater the delay in signals reaching a destination, so a high NVP is required for a good quality cable.

I don't know the formula either breff, I'll have a good google for it later.

Regards

Bellman


Service Engineer and all round nice bloke :-)

The views above are mine and NOT those of my employer.

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Guest

Oh, ok.

NVP with cables where the conduit is copper is approximately 130 meters in a microsecond (regarding the cable as mentioned above).

But capasitance depends also of cable lenght and is usually announced as pF / 1km .

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