Cabling for a Security System

Cabling for a Security System

I wanted to purchase a hardwire security system and I am going to do the wiring myself and was wondering if 2-strand 18 gauge wire would work for motion sensor, siren and door and window contacts. Or will I need to use four-strand for siren and motion sensor etc.?

This is a great project to undertake. While wireless systems are more easily installed, they also have to be maintained by replacing batteries on a regular basis. Hardwire systems, on the other hand, require very little maintenance. They also have the "hardwired" advantage that leaves no doubt that when a sensor trips, the controller knows about it.

Hardwired systems are more difficult to install because cables need to be run between the sensors and the controller. This can be a time consuming process depending on the constructions of your home. In my home, each door and window sensor took about one to two hours to install in a single-story home. If you have the opportunity to install the wiring during construction or renovation, the installation time will be much quicker.

Here is a breakdown on the types of wires that should be installed for each type of alarm device:


Motion Sensors

These sensors will need a minimum of four conductors in the cable between the panel and sensor. Two will be used to carry 12-volts DC from the controller to the sensor and two will carry the trip signal. Most sensors have an additional pair of contacts that can be used to detect tampering of the motion sensor. While this may be necessary for a commercial alarm system to meet UL requirements (and get business insurance), these terminals are often left un-connected in a home system. Some motion sensors also have an additional terminal for reporting any self-diagnosed failures to the alarm system. Use 8462 4 Conductor 22-ga. Unshielded cable for making the basic connections. Use 8-conductor if the motion sensor has the tamper and self-diagnosing terminals.


Door and Window Contact switches

These devices are passive and require no separate power from the alarm controller. Use 8460 two-conductor cable for these switches.




Passive Glass Break Sensors

Much like contact switches, there is no need for external power. Two-conductor cable will be fine.




Active Glass Break Sensors

Like motion sensors, these devices will use power and will need a minimum of four conductors. Use six-conductor cable if the tamper feature is hooked up.




Smoke and CO Detectors

These sensors will require four-conductor cable. Additionally, if more than one unit is installed, these sensors should be wired in a daisy-chain format where the cable comes into the sensor from the panel, then is run to the next sensor, and so on. All the smoke, fire, and CO detectors can usually be on the same zone of the alarm system unless you have more than five units. When more than five units on one zone, troubleshooting is more difficult. Use four-conductor cable for these units.


IR Beam Sensors

Like motion, smoke, and CO detectors; these units will need four-conductor cable. Two will be used for the power and two for the trip signal. Use six-conductor cable if the tamper feature is used.


System Keypads

All the hardwired systems we offer will require a four-conductor cable. Two of the wires will carry the power between the control panel and the system keypad. The other two conductors will carry the data that flows between the panel and keypads. Keypads wiring can be laid out in the daisy chain or home run format.


Telephone Connections

Alarm systems are designed to break into the telephone line and seize the line from any phone users in the home. Electrically, the alarm system is the first device the phone company "sees" in your home. The panel is wired in a series format and will require four-conductor telephone cable. Use either Cat. 3 or Cat. 5 cable between the alarm panel and the telephone distribution panel.


Intercom Stations & Voice Modules

One of our alarm systems has the ability to integrate an intercom system with the alarm controller. Generally speaking, intercom stations will need to use shielded cable between the intercom station and the intercom audio board. Shielded cable has a foil or braided wrapping around the conductors to help keep out electrical noise and interference. It's always best to check with the product's owner's manuals before ordering intercom wire, but you can rarely go wrong using four-conductor shielded cable like our 8482.


Computer Interfacing

If your alarm system is going to exchange data between a computer or home automation system, use Cat. 5 cable.

This versatile cable can carry data in many formats, be them RS-232, RS-485, or Ethernet. Use part number #8493 Category 5E Cable for this application.


X10 Control

Some of the alarm systems may have an option to control X10 Home Automation Products. These units will used the #1135 X10 TW523 Two-Way Interface Module to put the X10 commands onto the electricity lines. A cable will be needed between the panel and the location where the Two-Way Interface Module plugs into a regular electrical socket. Use the 1155B 7' RJ11 Connecting Cable, which resembles a regular telephone line cord. If an extension is required, use # 1270SCX Extension to get another 25 feet.


AC Power

The alarm system will need a connection between it and a plug-in transformer. The alarm system's transformer will convert the 120-volts AC into a lower voltage, usually 16.5 volts AC. At most, the transformer may supply up to two amps of current. Using four-conductor cable and doubling up two conductors on each terminal of the transformer will give better current flow with less resistance.


Sirens and Strobe Lights

12-volts DC powers most sirens and a strobe light so using two-conductor cable is ideal. In addition to outputting 12-volts DC to the siren terminals, some alarm systems can output the equivalent of an audio speaker output. A speaker siren will also need two-conductor cable.

The Weatherproof 30-watt 12-Volt Siren (7490.html) we offer has two different siren sounds. If your alarm system has separate outputs for fire and burglary, then use four-conductor cable for this run.


What About Cat 5 Cable?

Some folks have suggested using Cat. 5 cable for all their security sensor needs. While it is possible to use this cable for security sensor applications, it is not the ideal cable. The individual wire strands that make up a Cat. 5 cable are about one third thinner than typical 22 gauge wire. Over long distances, the thinner wire may present more resistance for the electricity traveling to a powered sensor. Additionally, if only a few of the conductors are used, there will be more of a mess at the control panel with extra wires all over the place. If you ever have to re-visit the panel, say two-years after it is installed, all those extra wires will slow your repairs or upgrades as you try to figure out what goes where.


What About Shielded Cable?

It is tempting to use shielded cable for all the runs between the control panel and the external sensors and keypads. Shielded cables have a layer of metal surrounding the conductors that helps keep out electrical noise. While one might think that this helps prevent false alarms, it may have the opposite effect. Some alarm panel manufactures have warned that this cable increases the capacitance on the zone. Under some conditions, this added line capacitance may cause the controller to think the sensor has tripped and a false alarm may result.


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