Cable Tray, Trunking or Conduit? Choosing Cable Containment for a Singapore Building

Containment is the part of a cabling job nobody photographs and everybody inherits. It decides what the cabling costs to install, what it costs to add to in five years, and whether the cables inside it stay within their bend radius and away from services they should not be near. Choosing between cable tray, trunking and conduit is not a matter of taste. Each one does a different job, and most buildings need all three in different places.

What is the difference between cable tray, trunking and conduit?

Open supports (tray, basket and ladder) let heat escape, are quick to lay cables into, and make it easy to add or trace a cable later. They are the normal choice wherever many cables run together out of sight.

Trunking is about appearance and protection where people work. It keeps cables tidy along a wall or a desk line and stops them being knocked or pulled. Its limit is capacity: once the lid is on and the trunking is full, adding a cable means taking the lid off along the whole run.

Conduit is about protection. It is right for a handful of cables that need to be shielded from weather, water, impact or tampering, such as a camera on an outside wall, a run across a plant yard, or a route cast into a slab. uPVC conduit suits outdoor, plant and wet environments. It is a poor choice for large bundles, because pulling many cables through a long tube is slow and can damage them.

How big should the containment be?

The commonest fault is containment sized for the cables on day one. It is full at handover, so the next contractor runs cable outside it, over the lid, or in a second tray fixed to the first. Within a few years nobody can trace a circuit, and the cables are packed tighter than they are rated to sit.

Three things are worth deciding on the drawing:

1. Spare capacity. Leave room for the cables that will come later. Many specifications set a maximum fill well short of full; if yours does not, agree one.
2. Access for pulling. A tray above a fixed ceiling with no access panel is a tray nobody can use. The route should be one a person can physically reach.
3. Bend radius. Fibre and high-category copper cables are damaged by tight bends. Corners, risers and drops need bends sized for the largest cable that will run through them.

Why does data cabling need to be kept apart from power?

Data and signal cabling run too close to power, or sharing containment with it, is a source of intermittent faults that are very hard to find afterwards. They show up as a link that passes on handover day and degrades under load, or a camera that drops off the network when plant starts up.

The fixes are cheap at first fix and expensive later:

• Separate containment, or a divided tray, for data and signal cabling and for power
• Distance between the two routes wherever they run side by side
• Crossings at right angles where a data route has to cross a power route
• Bonding and earthing of metal containment, done and recorded

Fibre itself is not affected by electrical interference, but the copper links, power feeds and devices it connects to are. That is why the separation should be planned for the whole route, not cable by cable.

What else should be settled before containment goes in?

• Fire stopping. Wherever containment passes through a fire-rated wall or floor, the opening has to be sealed again afterwards. Agree who does it and how it is recorded.
• Loads and fixings. Ladder rack and tray carrying heavy cables need supports at the right spacing and fixings suited to the structure. Tunnels, trackside and plant rooms have their own rules.
• Outdoor and wet areas. Choose materials that will not corrode, and drain or seal conduit so it does not hold water.
• Labelling. Mark trays and conduits so the next person knows what runs where.
• Who owns it. If one firm installs the containment and another installs the cabling, each will blame the other for a full tray or a tight bend. Where possible, have the same party design the containment and install the cables in it.

How does containment fit with the rest of the cabling job?

Containment comes before everything else in an installation, so its mistakes are the hardest to undo. In an office fit-out it has to be settled before the ceiling closes, covered in what to settle before the ceiling closes. In a data hall, density and airflow change the picture, covered in what changes once you are inside the hall. And it is one of the line items to check when you compare structured cabling quotations: a quotation that leaves containment out, or assumes it is someone else's, is not pricing the same job.

Where Fiber Tech sits

Fiber Tech Solutions Pte Ltd designs and installs cable tray, trunking, ladder rack and conduit, including uPVC conduit for outdoor and plant environments, and installs and certifies the cabling that runs in it. The work has been delivered across more than 100 substations island-wide, in MRT tunnels and depots on night engineering hours, and through the conduit and fibre rollout serving over 1,000 blocks. The company holds IMDA Wiring Contractor (Class) Licence No. IW105464 and has been a Singapore specialist contractor since 2007. To discuss a building or a route, get in touch.

— Written by the team at Fiber Tech Solutions Pte Ltd, IMDA-licensed wiring contractor and FOA-certified fibre specialists, Singapore.