Conduit for Surveillance ExplainedBy Ethan Ace, Published Jul 16, 2014, 12:00am EDT
Cameras frequently need conduit to protect wires and cables connecting them to the headend / recorder.
However, with so many types available, it is may be difficult to determine the right one to use in each application.
There are three types of metallic conduit common to surveillance systems:
- Electrical Metallic Tubing (EMT)
- Rigid Metal Conduit (RMC or simply "rigid")
- Liquidtight Flexible Metallic Conduit ("sealtight" or "liquidtight")
Additionally, there are two types of non-metallic conduit commonly used in surveillance:
- Rigid PVC conduit
- Electrical nonmetallic tubing (ENT)
In this note, we break down these types, their costs, and where they fit best.
This chart provides a very brief recap of each type of conduit reviewed here, their common applications, as well as their relative weight, damage resistance, and cost.
Electrical Metallic Tubing
EMT is the most common type of conduit used in commercial buildings. It has the thinnest wall of all the metallic conduits, and this limits its use to areas where it is not subject to severe physical damage, such as from vehicles or machinery. Contrary to popular belief, it may be used outdoors as long as wet location rated fittings are used.
Applications: EMT fits almost any application where it is protected from damage, indoors or out, wet or dry, including direct burial. In security, it is perhaps most commonly used as a "stub out" running from a camera, card reader, or other device location to above a suspended ceiling, so cables may easily be run down the wall without fishing.
Second, it is often used as a sleeve when running cables through walls and into network closets. Installers should make sure codes are observed and firestop applied to these sleeves where necessary.
It is also sometimes used for suspending cameras such as in open warehouses or retail stores, though long runs of smaller (1/2"-3/4") EMT used to hang cameras may wobble and vibrate causing shaky video.
Pros: EMT has the lightest weight of all the metallic conduits and many sizes can be bent easily using hand tools instead of hydraulic benders required for rigid conduit. EMT fittings and the conduit itself are the lowest cost of metallic conduits, as well.
Cons: Relatively easy to damage compared to rigid conduits, with dings and dents easily visible.
Cost: Price ranges from about $0.25 per foot for 1/2" conduit (often used for stubs and longer single camera runs) to about $2 per foot for 2" EMT (commonly used for sleeves). EMT is sold in 10' sections.
Rigid Metal Conduit
Typically simply called "rigid", this type of conduit consists of a much thicker wall than EMT, typically factory threaded at both ends. Because of this threading, any cutting of rigid conduit requires rethreading the cut end, and couplers and fittings must be threaded as well, unlike EMT which may use set screw connectors.
Applications: Because of its thickness, rigid metal conduit is used in areas cables may be subject to damage. Due to its higher cost and weight and the need to rethread, rigid is not normally used for long runs or stubs except where required by code. Larger sizes of rigid conduit (2" and up) are also sometimes used as poles to mount cameras.
Pros: Most damage resistant of all conduit types.
Cons: Highest cost and weight of all the metallic conduits. Requires specialized tools to rethread when cut. Bending typically requires hydraulic tools for sizes larger than 3/4", as opposed to hand tools used to bend EMT.
Cost: Rigid conduit ranges from about $1.50/ft. for 1/2" to about $5 per foot for 2". RMC is normally sold in 10' lengths.
Liquidtight Flexible Metal Conduit
Often simply called "flex" or "sealtite", this type of conduit consists of a flexible metal tube covered in a PVC jacket, making it suitable for use in wet locations.
Applications: Flex is most often used to connect from boxes to camera housings, seen below. Long runs of flexible conduit are difficult to keep neat and straight, making EMT or rigid typically a better choice.
Pros: Easy to install in applications where inflexible conduit would require multiple bends and/or connectors. Because of its PVC coating it has better resistance in locations which may cause other metallic conduits to rust or corrode.
Cons: Long, straight runs are more difficult, with poorer aesthetics than EMT or rigid conduits due to "wavy" looking installation. PVC jacket makes most flexible nonmetallic conduit unusable in plenum spaces.
Cost: 1/2" liquidtight, the most common size used, sells for about $1.00/ft. Generally sold in 50-100' coils. Larger sizes are available but generally not seen in surveillance.
PVC conduits are most commonly used in outdoor locations where cables are exposed to the elements. They are made from extruded PVC in two common wall thicknesses, called Schedule 40 and Schedule 80, each with different recommended uses. Unlike other conduits which use mechanical connectors, PVC conduits and connectors must be glued together, as they may not be threaded.
Applications: Rigid PVC conduit is used anywhere cables require weather protection. Schedule 40 is most used in general runs, where conduits are not buried or exposed to damage. Due to its thicker wall and better crush resistance, Schedule 80 is most often used when conduit is to be buried, encased in concrete, or exposed to vehicle traffic.
Pros: Low cost and light weight compared to metallic conduits. Glued push on connectors are easy to install.
Cons: Less resistant to damage than metallic conduits. Specialized paints must be used for PVC. Curves and bends require either heating the conduit and bending by hand (typically with a specialized heat gun or oven) or purchasing pre-made fittings, increasing cost and complexity.
Cost: 1/2" Schedule 40 PVC conduit sells for ~$0.16 per foot, while Schedule 80 sells for ~$0.30. Generally sold in 10' sections.
Electrical Nonmetallic Tubing (ENT)
This type of conduit consists of a flexible plastic material, which is often blue, giving it the nickname "Smurf tube." It's often seen in recent residential construction where some wire protection is needed, but metal conduit would be cost prohibitive. It is seeing increased use in commercial construction, however, especially for "stub outs" where EMT would normally be used.
Applications: ENT is most often used in concealed applications in walls or ceilings, or exposed in areas where aesthetics is not a concern, such as basements and crawlspaces. It is also commonly used as a stub out in place of EMT, connecting a device box to the ceiling above.
Pros: Low cost and light weight, easy to run with snap on connectors.
Cons: Least crush resistance of all conduit types, making it easiest to damage cables. May be easily penetrated by screws or nails during construction.
Cost: 1/2" ENT sells for about $0.25/ft., typically in coils of 100'.
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