Aircon Installation and Trunking in Renovations

Aircon installation is one of the few renovation items that touches almost everything else — the false ceiling, the electrical load, the wall finishes, and even the facade. Plan it well and the pipes and trunking vanish into the ceiling; plan it badly and you live with ugly boxing, a noisy unit, or water dripping where it should not. In Singapore’s climate, the aircon is not a luxury, so it deserves proper attention during a renovation.

This guide covers aircon installation in a renovation context: concealing the trunking, sizing the units, getting the condensate drainage right, the rules around condenser placement, and when in the renovation the work should happen. It is written for homeowners coordinating a renovation, so the focus is on the decisions that affect how the finished home looks and performs.

Concealed versus exposed trunking

The refrigerant pipes, drainage, and cabling that connect an indoor fan-coil unit to the outdoor condenser have to run somewhere. The defining choice is whether they are concealed or exposed.

Concealed trunking — the pipes run inside a false ceiling and down within a wall or a built-in feature, so nothing is visible. It gives the cleanest look and is the norm in most renovations, but it must be planned and installed before the false ceiling is closed.
Exposed (surface) trunking — the pipes run in a plastic trunking box fixed to the wall or ceiling surface. It is cheaper and easier to service, but the boxing is visible and rarely looks good in a finished living space.

Most homeowners conceal trunking in the main living areas and accept exposed trunking only in service areas. Because concealment depends on the false-ceiling work, the aircon piping must be coordinated with the ceiling contractor and slotted into the renovation sequence at the right moment — after wiring, before the ceiling closes.

Sizing the units (BTU) correctly

An aircon that is too small never cools properly and runs constantly; one that is too large cycles on and off, wastes energy, and leaves the air clammy. Correct sizing, expressed in BTU, depends on the room’s floor area, ceiling height, sun exposure, glazing, and how the room is used.

As a rough guide, larger and west-facing rooms with big windows need more capacity, while small, shaded bedrooms need less. Rather than guessing, have the aircon contractor calculate the load per room and choose a system accordingly — a multi-split system serving several rooms from one condenser is common in flats because it limits the number of outdoor units. Look for a good NEA energy efficiency tick rating, because the aircon is one of the largest electricity consumers in a Singapore home and a more efficient unit pays back over its life.

Condensate drainage — the detail that causes leaks

The most common aircon failure in Singapore is not the unit but the drainage. Each indoor unit produces condensate water that must drain away by gravity to a proper discharge point. If the drainage pipe lacks sufficient fall, sags, or is poorly routed, water backs up and eventually drips through the ceiling — a frequent and avoidable cause of damage.

Insist that the condensate pipe runs with a continuous gradient to the drainage point, with no low spots, and that the discharge is to an approved location rather than draining onto a neighbour’s property or the facade. Where gravity drainage is not possible, a condensate pump can be used, but a well-planned gravity run is more reliable. This is exactly the kind of hidden detail that separates a careful installer from a cheap one, and getting it wrong is among the costlier renovation mistakes to avoid.

Condenser placement, ledges, and rules

The outdoor condenser needs a proper location — typically a designated aircon ledge — with enough clearance for airflow and access for servicing. In HDB flats, condensers must be installed on the provided aircon ledge and there are rules on placement; in condominiums, the MCST and the building’s by-laws may govern where and how units are mounted, and approval is often required. Always check the relevant rules before assuming a position is allowed.

Poor condenser placement causes hot air recirculation (which kills efficiency), drainage problems, and servicing difficulties. Ensure the ledge can take the weight and that the unit is mounted securely, level, and accessible. If your renovation involves any change to the facade or external mounting, confirm what approvals are needed — for condos this routinely means going through the MCST, a process we touch on in our guide to A&A works in Singapore.

Timing, electrical load, and coordination

Aircon work has to be sequenced carefully because it interacts with the ceiling and the electrical installation. The piping and drainage go in after the electrical first-fix and before the false ceiling closes; the indoor units and final connections come later. Because the aircon adds significant electrical load, the circuits and isolators must be sized and installed by a Licensed Electrical Worker, and the consumer board must be able to take the load.

Coordinate the aircon contractor, the ceiling contractor, and the electrician so that nobody works against another. A good main contractor or interior designer manages this overlap; if you are running trades separately, you must manage it yourself. Budget for the system honestly — the units, piping, trunking concealment, and electrical work together are a meaningful line item, which we set in context in our renovation cost guide.

Frequently asked questions

When should aircon be installed during a renovation?

The aircon piping and drainage should be installed after the electrical first-fix and before the false ceiling is closed, so the trunking can be concealed. The indoor units and final connections come later. This timing has to be coordinated with the ceiling contractor and electrician.

Should aircon trunking be concealed or exposed?

Concealed trunking running inside the false ceiling gives the cleanest look and is standard in living areas, but it must be planned before the ceiling closes. Exposed trunking in a surface box is cheaper and easier to service but visible, so it is usually accepted only in service areas.

Why does my aircon leak water through the ceiling?

The most common cause is poor condensate drainage — a pipe without enough fall, with sagging low spots, or routed badly — so water backs up and drips through the ceiling. A continuous gradient to an approved discharge point, installed carefully, prevents this common failure.

Do I need approval to install aircon in a condo?

Often yes. In condominiums the MCST and the building’s by-laws may govern where and how condensers are mounted, and approval is frequently required, especially if the facade is affected. Always check the relevant rules before assuming a condenser position is allowed.

How do I size an aircon for a room?

Sizing depends on floor area, ceiling height, sun exposure, glazing, and how the room is used, expressed in BTU. Rather than guessing, have the contractor calculate the cooling load per room and choose a system with a good NEA efficiency rating, since an oversized or undersized unit performs poorly.

Coordinating aircon, ceiling, and electrical work and want it sequenced properly? Talk to our consultancy or get in touch.