Conduit and Cable Trunking in Ireland

Short answer: conduit is a round tube you draw cable through. Trunking is a rectangular duct with a lift off lid you lay cable into. Both protect cable and both let you alter a circuit later without opening a wall. Conduit, trunking and fittings are counter items at Shamrock Electrical in Rathcoole, so ring the counter on 01 401 9907 or email sales@shamrockelectrical.ie with sizes and quantities.

What is the difference between conduit and trunking?

Conduit is a round tube you draw cable through after it is installed. Trunking is a rectangular duct with a removable lid you lay cable into.

That one difference decides most jobs. Conduit is a sealed route, so the cable goes in by draw wire once the run is fixed and glued. It gives good mechanical protection and looks tidy on a wall or ceiling, but adding a circuit later means drawing more cable through the same tube, and there is a limit to how much you can pull.

Trunking opens along its length. Lift the lid and every cable in the run is in front of you, which is why it is the default anywhere circuits get added, moved or taken out. Offices, workshops, plant rooms and server cupboards are almost always trunking for that reason.

In practice a lot of installations use both: trunking for the main horizontal distribution at high level, then conduit dropping down to individual outlets and switches.

What size conduit or trunking do I need?

Work to a 45 percent space factor, so cables occupy under half the duct. Going one size up costs very little and saves a rewire later.

The space factor is not just tidiness. Cables bunched tightly together cannot shed heat, so the current they can safely carry drops, and a full conduit is close to impossible to draw into without stripping insulation on the way through.

Common domestic and light commercial sizes are 20mm and 25mm PVC conduit, and 16x16mm or 25x16mm mini trunking for surface runs. Distribution trunking is typically 50x50mm or 100x50mm. Larger sizes are available and are usually an order in item rather than a shelf item.

The rules that govern this in Ireland are I.S. 10101, the National Rules for Electrical Installations. Where a run is long, bunched with other circuits, or passing through a warm space, the cable size itself needs calculating rather than assuming, and that calculation is the contractor's call.

Should I use PVC or steel conduit?

PVC suits most installations and is much faster to work. Steel is for impact risk, industrial settings, and where the conduit itself is used as the earth path.

PVC conduit is cut with a hacksaw, bent cold with a spring, and joined with solvent cement. One person can install a lot of it in a day. It does not corrode, which matters in damp plant rooms, and it is the normal choice for domestic and commercial work.

Steel conduit takes real mechanical abuse, which is why it appears in factories, workshops, car parks and anywhere a forklift or a trolley might meet a wall. Properly installed and bonded, a steel system can serve as the circuit protective conductor, though many contractors still pull a separate earth for certainty.

Flexible conduit is a third category and is used for the final short connection to anything that moves or vibrates, such as a motor or a machine. It is not a substitute for a fixed containment run.

Where is mini trunking used?

Mini trunking carries cable along a surface where chasing into the wall is not practical, typically 16x16mm or 25x16mm in homes, offices and retail units.

It is the usual answer in a solid wall, a rented unit where you cannot cut chases, a dry lined wall already finished, or any job where the work has to be reversible. It takes paint, so on a painted wall a run of mini trunking largely disappears.

The fittings matter more than the length. Internal angles, external angles, flat bends, tee pieces and stop ends are what make a run look deliberate rather than improvised, and running out of one fitting halfway through a job is the usual reason a run gets butchered. Count fittings before you come in, not just metres.

Can I install conduit and trunking myself?

Fixing the containment is straightforward work. The moment cable is connected into a circuit, the job is electrical work and belongs with a registered electrical contractor.

There is a genuine and useful distinction here. Mounting trunking, running empty conduit and leaving a draw wire in it is carpentry with a spirit level. Terminating conductors, altering a distribution board or energising anything is not, and in Ireland that work sits under I.S. 10101 and must be carried out and certified by a registered electrical contractor.

This is also the single cheapest thing a self builder can do for a house: run empty conduit with draw wires to the places you might want a cable in five years. Adding a circuit later becomes a morning's work rather than a replastering job.

Where can I buy conduit and trunking in Dublin?

At the Shamrock Electrical trade counter in Greenogue Business Park, Rathcoole, just off the N7 and well positioned for the M50. Conduit and trunking are counter items.

Conduit, trunking, fittings and the associated fixings are not sold through the website. They are bulky, they are almost always bought by the length and the box, and the right answer depends on what the run actually looks like. It is faster to describe the job on the phone than to guess at a basket.

Website prices are retail. Trade pricing on containment is set by account and by quantity, so ring the counter on 01 401 9907 or email sales@shamrockelectrical.ie with sizes, lengths and fitting counts and we will price it properly.

We have been supplying Irish contractors from Rathcoole since 2016 and hold accounts with the main containment manufacturers, so items we do not hold on the shelf are usually a short order in rather than a dead end. Ring before travelling if the quantity is large.

Trade counter details

Shamrock Electrical, Unit 22, Block 613, Jordanstown Road, Greenogue Business Park, Rathcoole, Co. Dublin, D24 TX98.

Phone 01 401 9907. Email sales@shamrockelectrical.ie.

Opening hours: Monday to Friday 7am to 5pm, Saturday 9am to 1:30pm, closed Sunday.