Protecting Hearth and Home: Don’t compromise security with an improperly wired alarm system

By Mark C. Ode | Apr 15, 2021




I recently had a home security system installed. It was vastly different from the systems I have had in my other homes over the years. It is certainly much different than the residential and commercial systems I installed as an electrical contractor in the 1980s.

Almost half of my business then was dealing with wired fire alarm and security systems. It was obviously much easier to prewire in new construction than to retrofit existing commercial buildings or homes. Security fixed wiring in existing or finished buildings required ingenuity with some structural repair.

My new security system was mostly wireless, took less than three hours to install, and did not require any structural repair. I was extremely interested in watching and questioning the installer, who works for one of the major security monitoring companies, and observing whether the installation complied with the National Electrical Code. I was probably his worst nightmare since I questioned his methods, especially for the hardwired part of the system.

I remembered having customers follow me around asking questions when I was doing electrical wiring. Because I was an NEC instructor in the local community college and teaching apprenticeship classes, I was well-equipped to explain the reasons why I did various things.

While my young installer was competent, he did not have a deep understanding of the NEC requirements covering security systems. Since many municipalities do not inspect low-voltage wiring, electrical contractors doing security and fire alarm systems wiring may not be as knowledgeable as they should be about Article 725, which covers Class 1, Class 2 and Class 3 remote-control, signaling and power-limited circuits.

Don’t misunderstand me; the municipalities in your area may in fact require permits and do require compliance with Article 725 covering low-voltage wiring for security systems. Many municipalities do not consider low-voltage systems to be a safety issue, however, and this misunderstanding should be corrected, since there are definite safety issues dealing with low-voltage wiring.

While Class 2 low-voltage systems are not normally a shock hazard or a fire ignition hazard, Class 3 circuits can be a shock hazard, and Class 1 circuits are both a shock and a fire hazard, even with power-limited Class 1 systems. A power-limited Class 1 system has a maximum voltage of 30V, a maximum volt-ampere (VA) level of 1,000 VA, and a maximum ampere level of 33.33A. Even as power-limited applications, Class 1 systems can be dangerous.

Compliance with Article 725 for security systems is critical for electrical safety. For example, where installing low-voltage cable from a small Class 2 transformer at a receptacle inside the home through the wall to an outside camera, low-voltage cable cannot occupy the same box as the 120V circuit. A low-voltage Class 2 cable, installed in the same box as the 120V circuit, is a safety issue since insulation failure from the 120V conductor to a low voltage conductor could be a fire issue, as well as a potential shock issue.

Most security system cameras mounted on the side of a house and doorbell cameras at front and back doors for residential applications are connected to low-voltage Class 2 cables and are in wireless Wi-Fi connection to the security system control panel and to people’s cell phones. These devices provide actual real-time visual connection to short- or long-term storage of images and videos.

More sophisticated cameras use power over ethernet (PoE) where two of the four low-voltage wires in the cable are used to position the cameras, while the other two wires are used to communicate between the camera and the security panel with access to your cellphone. If using PoE technology in your home, make sure the cable used can handle the voltage necessary for the system and that the cable can carry the amount of current necessary for the load of the camera.

The safety provided by the home security system should not be compromised by improper wiring with possible shock hazards and fire hazards. Proper installation of a security system will provide long-term service and reliability, but should be installed in compliance with Article 725, even if your municipality does not require a permit or an inspection of low-voltage systems.

About The Author

ODE is a retired lead engineering instructor at Underwriters Laboratories and is owner of Southwest Electrical Training and Consulting. Contact him at 919.949.2576 and [email protected]

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