Installing conduit is one task you can’t get around when you solar power your house yourself.
If a solar installer ever tries to install a PV system on your house without using conduit to protect the wiring, you may want to call the power company and ask them if conduit installation is necessary with PV systems? If they say yes (which they will), fire him immediately before he burns down your house.
What Is Conduit?
Before you learn how to install conduit, let’s first learn exactly what conduit is.
Conduit is a hard, durable protective tubing that completely covers and protects wires or cables used in electrical applications that typically need protection from exposure to sunlight and other elements.
When installing conduit, wire is pulled through the conduit tubing and then typically passed through walls, under driveways, secured to the exterior, and even to the interior of a house. Basically conduit installation protects the wires running through your walls, underground, on your roof, or down the side of your house.
Types of Conduit
Some of the more popular types of conduit that are used in electrical work include rigid-steel, electrical metallic tubing (EMT), rigid non-metallic (poly vinyl chloride – PVC), and flexible metallic and nonmetallic conduit.
Rigid-steel conduit is the strongest type of conduit casing and sort of resembles a thick metal pipe that is threaded on both ends. Due to its superior strength and durability rigid-steel conduit is considered to be one of the best choices for protecting wires when installing conduit.
However, this also makes it the hardest conduit to bend or cut and sometimes requires a professional to do it right. To cut it yourself, you’ll need a hacksaw or a pipe cutter and possibly a clamp or vise to keep it from moving. Cut at a 90° angle.
After cutting (and before conduit installation), you’ll need to file the sharp edges down and thread the conduit so you can use threaded couplings, locknuts, and bushings.
To bend rigid-steel conduit, you can use a manual bender or have it factory bent, however, factory bending is much more expensive.
Rigid-steel conduit is available in sizes from 1/2 inch to 6 inches in diameter and up to 10 feet in length.
For installing conduit in damp areas or underground, galvanized steel conduit is used to prevent moisture and rust.
Electrical Metallic Tubing (EMT)
Electrical metallic tubing conduit (also known as thin-wall conduit) is similar to the rigid-steel type, but the walls are 40% thinner, which makes it easier to bend but relatively less durable.
In other words, electrical metallic tubing conduit is easier to shape but not as tough.
To cut electrical metallic tubing conduit, you’ll need a hacksaw or tubing cutter and possibly a clamp or vise to keep it from moving. Cut at a 90° angle. After cutting, you’ll need to file the sharp edges down before installing conduit.
An EMT bender can be used to bend EMT conduit.
Electric metallic tubing (EMT) conduit is available in sizes from 1/2 inch to 4 inches in diameter and up to 10 feet in length.
Rigid Nonmetallic (PVC) Conduit
Rigid Nonmetallic Conduit (also known as PVC conduit) is made of rugged plastic and thus is ideal for underground conduit installations including direct burial and concrete encasement installation. Installing conduit that is made out of plastic is cheaper, plus it’s strong, waterproof, and has a low absorption rate.
To cut it, you’ll need a hacksaw or tubing cutter and possibly a clamp or vise to keep it from moving. Cut at a 90° angle. After cutting, you’ll need to file the sharp edges down.
PVC conduit is available in sizes from 1/2 inch to 5 inches in diameter and up to 20 feet in length.
Flexible Metallic Conduit
Flexible metallic conduit is made of either steel or aluminum and is typically used for conduit installation in areas where there may be movement or vibration. You can also get it for use in wet conditions.
To cut it, you’ll need a hacksaw and possibly a clamp or vise to keep it from moving. Cut at a 90° angle.
Flexible metallic conduit is available in sizes from 3/8 inches to 4 inches in diameter and you can basically get any length you want.
Installing conduit consists of measuring out the length of the conduit, cutting, threading, and bending it to fit the requirements of your project, installing the fittings and supports, securing the conduit into place and installing the couplings/connectors, connecting to the outlet boxes, pulling the conductor (wire) through the conduit tubing and making/, securing, and testing the connections.
When installing conduit make your runs of conduit as straight and direct as possible and avoid any unnecessary bends.
How To Install Conduit Fittings, Connectors and Couplings
Fittings for EMT conduit come in both 3/4″ water-tight for installing conduit in wet areas and non-water tight for dry areas.
Concrete-tight and water-tight connectors and couplings are also required for concrete and wet applications respectively.
Fittings for rigid-steel and PVC conduit are similar to EMT fittings. You can get threaded or threadless couplings and connectors for rigid-steel and PVC conduit. With threadless, there is no threading of the conduit required. EMT conduit is too thin and cannot be threaded, therefore uses only threadless couplings and connectors.
On rigid steel conduit installation, threaded couplings are screwed onto the threaded ends of the conduit and a pipe wrench is used to tighten them. Rigid-steel and PVC conduit is connected to electrical boxes using locknuts and bushings.
Fittings for flexible metallic conduit are attached to the conduit either by screwing them on (internally) or with clamping screws (externally). For installing conduit in wet areas, liquid-tight fittings are used.
The next part of the process involves connecting the conduit pieces together. PVC conduit connections are welded together using a solvent cement resulting in a strong, water tight bond. Just coat them in primer and apply some cement to each piece of PVC to stick them together. Since PVC is plastic, it can be cut easily with a regular fine tooth saw.
In conduit installation, all pieces of conduit are connected with what is called a “conduit body.”
A conduit body is a special kind of fitting that functions a lot like a junction box and is used in between connecting conduit pieces to keep the number of bends to a minimum. This is because most electrical codes require you to keep your total bends for one piece of conduit to 360° and under.
So if when installing conduit, you had 4 bends of 90°, you would need to install a conduit body. And with 8 bends of 45°, you’d need to install a conduit body. You get the idea.
Straps or hangers are used to support all conduit throughout the entire run.
Only after you have finished installing conduit and securing it to the electrical boxes, can you pull the conductor (wire) through and make your final connections to the photovoltaic components.
In a solar power system without conduit, your outdoor wires could get wet and eventually corrode. Your PV system would likely suffer extensive and expensive damage.
Also, without conduit, the wires in your walls could heat up and start a fire. Installing conduit is necessary to protect your wires from all exterior or interior elements and vice-versa.