When we plan to do for electrical wiring,we need to use a conduit system to protect an electrical cable from damage due to mechanical or biological.It also make electrical wiring look nice and proper arrangement.
As an electrician,a knowledge about conduits is important to decide which types are suitable for our wiring application and structure.If we choose a wrong types,it can cause the serious damage,increase cost for material and also can reduce wiring life span.
An electrical conduit system is designed for electrical piping system used for wiring installation.It made electrical wiring more easy to installed and have a proper way. Electrical conduit may be made of metal, plastic,fiber, or fired resistance material.
Types of conduits
Conduit systems are classified by the wall thickness of tubing, mechanical stiffness of the tubing, and material used to make the tubing.
Tubing with thicker walls in the same material offers better protection from impact, but increases the weight and cost of the conduit and also increases labor cost to install the system.
Around the world,we can choose several types of conduits material depend on our wiring types and application.Below i listed for our basic knowledge and reference.
1) Rigid Metal Conduit (RMC)
Rigid Metal Conduit (RMC) is a thick threaded tubing, usually made of coated steel,though it may be aluminum.It normally used for high standard building because it have high resistance from mechanical impact.It can make the wiring more long lasting.
2) Rigid Nonmetallic Conduit (RNC)
Rigid Nonmetallic Conduit (RNC) is a non-metallic unthreaded tubing.
3) Galvanised rigid conduit (GRC)
Galvanised rigid conduit (GRC) is galvanised steel tubing, with a tubing wall that is thick enough to allow it to be threaded. Its common applications are in commercial and industrial construction.
4) Electrical metallic tubing (EMT)
Electrical metallic tubing (EMT), sometimes called thin-wall, is commonly used instead of galvanized rigid conduit (GRC), as it is less costly and lighter than GRC. EMT is not threaded.
Lengths of conduit are connected to each other and to equipment with clamp-type fittings. Like GRC, EMT is more common in commercial and industrial buildings than in residential applications. EMT is generally made of coated steel, though it may be aluminum.
5) Electrical Nonmetallic Tubing (ENT)
Electrical Nonmetallic Tubing (ENT) is a thin-walled corrugated tubing that is moisture resistant and flame retardant. It is pliable such that it can be bent by hand and is often flexible although the fittings are not. It is not threaded due to its corrugated shape although the fittings might be.
6) Liquid tight Flexible Nonmetallic Conduit (LNFC)
Liquid tight Flexible Nonmetallic Conduit (LNFC) refers to several types of flame resistant non-metallic tubing. Interior surfaces may be smooth or corrugated.
There may or may not be integral reinforcement within the conduit wall. It is also known as FNMC.It normally used for high risk for fire wiring such as server room or main switch room.
7) Aluminium conduit
Aluminium conduit, similar to Galvanized Metal Conduit (GMC), is a rigid conduit,generally used in commercial and industrial applications, where a higher resistance to corrosion is needed.
Such locations would include food processing plants, where large amounts of water and cleaning chemicals would make galvanised conduit unsuitable.
Aluminium cannot be directly embedded in concrete, since the metal reacts with the alkalies in cement. The conduit may be coated to prevent corrosion by incidental contact with concrete.
The extra cost of aluminium is somewhat offset by the lower labour cost to install, since a length of aluminium conduit will have about one-third the weight of an equally-sized rigid steel conduit.
8) Intermediate metal conduit (IMC)
Intermediate Metal Conduit (IMC) is a steel tubing heavier than EMT but lighter than RMC. It may be threaded.
9) PVC conduit
PVC conduit is the lightest in weight compared to other conduit materials, and usually lower in cost than other forms of conduit.This type is common used around the world for electrical wiring.
The various fittings made for metal conduit are also made for PVC. The plastic material resists moisture and many
corrosive substances, but since the tubing is non-conductive an extra bonding (grounding) conductor must be pulled into each conduit.
PVC conduit may be heated and bent in the field.Joints to fittings are made with slip-on solvent-welded connections,which set up rapidly after assembly and attain full strength in about one day.