1 intrusion alarm technology cabling for burglar alarms

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INTRUSION ALARM TECHNOLOGY

CABLING FOR BURGLAR ALARMS

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Cabling for alarm systems doesn’t follow the same cabling standards that are used for the telecommunications industry.

Therefore there are no limitations on cable distances with the exception of voltage drops for detectors that require power, PIRs are an example of a detector that requires two leads for power and two leads for a signal.

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Furthermore terminations are simply made to screw terminals utilizing form C contacts and don’t have twist rates to maintain.

Form C contacts are single-pole, double throw contacts. They have three terminals, a Common, a Normally Open and a Normally Closed. When the energizing force is NOT present the Common terminal is connected to the Normally Closed terminal. When energized, the Common terminal disconnects from the Normally Closed terminal and connects to the Normally Open terminal.

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Zone wire is not a high speed data transmission line, it is a simple signaling path that sends a 5V to 10V signal down the cable at a low bandwidth.

The installation of alarm systems still requires that all work is done in a neat and workman like manner, NEC article 110.12.

Intrusion alarm falls under NEC article 725; Class 1, Class 2, Class 3 remote control, signaling and power limited circuits.

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Security systems utilize Class 2 or Class 3 (CL2, CL3) type cables.

The cable types are 22/2, 22/4, 18/2, 18/4 and 14/2 or 14/4 for smoke detectors.

The designations are as follows; 22AWG with 2 conductors (22/2).

Remember that the larger the AWG number the smaller the conductor is.

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Wiring window contacts for the first floor, you leave a small loop at each location, the next slide will show the elevation view of this.

IN STICK FRAME CONSTRUCTION THESE LOCATIONS WOULD BE WIRED DOWN FROM THE ATTIC OR UP FROM THE BASEMENT.

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When installing cable for each zone you will leave a loop at each location and come back later to terminate them.

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Here is what a series loop will look like when it is physically wired.

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Here is what a parallel loop will look like when physically wired.

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As you have just seen in the previous slide splicing is an acceptable practice in burglar alarm wiring, in fact its practically a necessity.

Dolphin clips are the preferred method of splicing two conductors together.

THE TOP OF THE CRIMP IS OPEN SO A TEST PROBE CAN BE PLACED INTO IT TO CHECK FOR CONTINUITY

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The standard procedure for securing wire in alarm installs has been to staple it to the wooden studs, (attics and basements).

A T-25 staple gun is used for the installation.

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Notice that the staples are U shaped to easily fit over the 22 AWG cable.

Care should be exercised when using staples for obvious reasons, shorting conductors is one possible problem.

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Bearing down to hard on the staple gun and using staples that are too small will cause false alarm issues in the form of cold shorts.

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Bridle rings or small J-hooks can be used for horizontal cable runs that will contain several cables, and where applicable beam clamps are used for support.

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Tie wrap buttons or tie wraps with screw wholes can also be used to support the cabling.

Again care should be taken to not cinch the tie wraps down to tight onto the cables.

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Some detection devices require four conductors, two for power and two for the signal path or detection loop.

PIRs require a 22/4 for this purpose, for longer runs an 18/4 can be used to compensate for voltage drops.

The following slide shows the formula for calculating cable voltage drops.

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Given a 22 AWG with a load current of .5 amps at 350 feet long what would the voltage drop be.

350’ divide by 100 (100 is a constant) = 3.5 X 1.60 (from the chart) = 5.6 volts.

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The percentage of the voltage drop loss is determined by dividing the voltage drop (VD) by the source voltage.

5.6 / 12 = 46%, that’s almost half of the voltage lost on a 22 gauge wire over 350 feet long.

What is the voltage drop if we use 18 gauge?

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350/100 = 3.5 3.5 X .64 = 2.24 volts.

2.24/12 = 18% volts

In this case 18 gauge wire would be needed for a 350 foot run for the PIR to function properly.

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Any alarm cabling installed in a plenum space must be rated for plenum, CL2P or CL3P.

Installations in vertical risers shall be riser rated, CL2R or CL3R.

Horizontal cabling is general purpose cable CL2 or CL3, all of the listed cables help stop the spread of fire.

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All splice shall be made in an approved enclosure and should be readily accessible for servicing.

All intrusion alarm cable must have it’s own independent support system and shall not be attached to any conduit or ceiling hangars.

A small service loop should be left at both ends of each cable run.

1 intrusion alarm technology cabling for burglar alarms

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