Installation of your security system begins from the ground up—literally. In fact, it begins below ground with conduit runs.
All underground electrical wiring, including the low-voltage security system, needs to be installed in PVC conduit. Electrical conduit is gray and available at most building-supply and hardware stores. Electrical fittings ensure wire is not nicked or damaged during installation. All joints should be connected using PVC glue. Conduit should be buried a minimum of 12 inches below grade.
Conduit needs are usually communicated between the security installer and electrician or general contractor. In general, electrical-conduit runs are going to the same place as the security system. Usually the electrician will lay the conduit for security because it’s more cost-effective and helps avoid the security installer cutting through the electrician’s conduit, and vice versa.
The two conduits may be laid in the same trench, but there needs to be at least 12 inches of separation. This eliminates the “noise” that can bleed through between high and low voltage. If this is not adhered to, the problems you may have later on would only be correctable by separating the lines, which is an expensive solution.
Once the PVC conduit comes out of the ground, it should connect to metal conduit; but it should be 6 to 12 inches above ground before converting. Installing PVC to a metal fitting below ground will allow water to seep into the conduit and cause problems later.
There are two types of metal conduit fittings: indoor and outdoor. Outdoor fittings may be used inside, but indoor fittings should never be used outdoors. The risk of water entering the conduit can cause shorts, wire deterioration and damage.
With long wire runs, junction boxes should be placed periodically. This allows for easier wire pulls and prevents the overstressing of wires. Metal conduit should be fastened or supported. When connecting to a moving or vibrating object such as a gate operator, flex conduit or fittings are required. Using a bender instead of 90-degree fittings makes for a smoother installation and lowers wire stress.
When it comes to conduit runs, more is better. The diameter is also important. Even if you’re not planning on having security throughout the buildings, it’s best to use a two-inch minimum. Undersized conduit and junction boxes will make the job difficult or impossible.