Installing new wiring in any larger indoor or underground electrical installation often means that you’ll also be using the appropriate conduits to shield wires and cables from unfavourable external factors. This includes heat, UV radiation, moisture, and mechanical stresses that can cause unwelcome damage. In addition, conduits prove handy in preventing common electrical faults, such as electrical fires. And they help with getting neatly organised routing, making access to the wiring inside simple and any necessary repairs a breeze.
While there are half a dozen of different conduit types to choose from, it’s corrugated conduits that see the most use in Australia. These are well suited to typical Australian conditions and are designed according to strict regulations set out in the AS/NZS 2053 standard.
What is a Corrugated Conduit?
A corrugated conduit is a type of non-metallic, flexible conduit, usually made of PVC. It is durable, easy to bend, and even easier to install. This makes tight spaces like corners accessible and considerably cuts down on installation times and costs. No specialised tools are required and separate conduits can be joined by simple conduit fittings in the same or similar materials.
Where Is It Used?
Corrugated conduit comes in two basic types – medium and heavy-duty. Medium-duty conduits are often grey in colour (or white for data cabling) and are usually used in indoor and above-ground wiring. Heavy-duty variants are orange, often in wider diameters, and have thicker internal walls for added protection. These are commonly used in underground wiring.
Why go with PVC Corrugated Conduits?
The corrugated designs aid in wire protection and routing while also being easy to bend by hand, even at room temperature. The choice of PVC as the main ingredient also helps in this respect, The material is lightweight, flexible, waterproof, resistant to heat and combustion, and fares well against corrosive substances and chemicals in general. And it can work in temperature extremes ranging between -25 and +100 Centigrade. PVC corrugated conduit is made with by feeding PVC pellets into a twin-screw extruder under heat and pressure. The process also means that once cooled it maintains its stability and strength. The attaching fittings are also PVC but made using pre-cast moulds.
Besides PVC, corrugated conduits are available in other polymers, such as PU (Polyurethane) which is more resistant to impact and wear, PP (Polypropylene) as a more eco-friendly choice but also flammable and polyamide or Nylon variants that have high flexing strength but are outdone by PVC in outdoor applications due to the latter’s high UV resistance.
A metallic rigid conduit may be stronger and more durable but requires complex tooling and bending procedures to fit within designated bends and tighter spaces, such as around piping. This significantly ups installation time and labour costs. The initial lower price of flexible corrugated conduits also means there are significant savings in longer conduit runs.
Things to Consider
When buying conduit, consider where and how it will be used. This means the types of wiring it needs to fit inside, and hence the overall diameter and length that you need to source for your project. Common diameters are 20, 25,32, 40, and 50mm for both grey above-ground and orange underground conduit, with the 25mm type being the most widespread in different wiring applications. The diameters also mean that there needs to be enough room for the wires and cables to allow for easy fitting and removal. Wire and cable types shielded in corrugated conduits include twin and twin and earth, coaxial and optic fibre data cables, and building wire in underground connections. The AS/NZS 20253 standard also states the maximum wire and cable size that can be used in differing conduit diameters.
Corrugated electrical conduit is often sold in coils of different lengths. Common coil lengths are 10, 20, 25 and 50 metres, so getting what’s right without overpaying is easy.
The Role of Fittings
Individual conduit runs or separate pieces are easy to connect using the appropriate fittings. There are different types, such as couplings, tees, bends, sweep bends, elbows, junction boxes, and adapters among others. Often corrugated conduit glue is used in conjunction with fittings to ensure a tight, sealed fit, and prevent the buildup of moisture. Glue is different in medium and heavy-duty conduit connections.
When mounted to walls and ceilings, the conduits are often held in place with half or full metal or PVC electrical saddles. The usual practice is to use galvanised metal or PVC saddles outdoors and in corrosive environments. Saddles also need to be evenly spaced to prevent sagging and are affixed to walls using nail-in anchors, wall plugs, or screws.
So, to wrap things up, corrugated conduit comes in medium and heavy-duty variants distinguishable by colour, shields different types of cables and wiring, is flexible, durable and easy to install, and to boot is decently priced. in addition, there are many accessories like fittings and saddles that make routing and wire management simple and quick. Look for conduit and fittings in your nearest hardware store.