HDB Aircon Installation Rules: Ledge, Condenser and Installer Checks Before You Renovate
Aircon is on almost every Singapore renovation list, whether you are fitting a new BTO, adding a unit to a resale flat or replacing an old system. In an HDB flat, the installation follows HDB's own guidelines, and BCA has its own rules for units fixed outside or projecting from a building. A few of these decide where the condenser can go and what your installer has to do.
This guide sums up what HDB and BCA say about aircon installation. It is general information, so check the latest rules for your own flat with HDB before you start.
Who can install your aircon
According to HDB's renovation guidelines for air conditioner installation works, you are responsible for the proper installation, safety and stability of your air conditioner, whether it is a casement, window or split type unit. HDB requires air conditioners to be installed by a BCA trained air conditioning condensing unit installer.
BCA's air-conditioning safety page adds that only trained installers may install a unit outside or projecting from a building, and that the installer should have an identification pass and be registered with BCA. BCA publishes a list of trained installers that owners can check.
The paperwork after installation
Installation report: HDB says you need to submit an installation report to the HDB Branch managing your flat within 14 days after installation. BCA notes the trained installer must submit the report no later than 14 days after completion, using Form AC-02 for HDB flats.
New wiring: the SP Services Form CS/5H endorsed by HDB must be submitted to SP Services for testing of any new wiring.
Your main switch rating decides the permit
Just as with other electrical works, the rules depend on whether your flat has a 30amps or 40amps main switch. Our HDB electrical works guide explains how to tell.
Flats with a 30amps main switch:
Existing point: installing an aircon using an existing approved 15amps power point or 20amps isolator does not need a permit.
New point: using a new 15amps power point or new 20amps isolator needs an electrical permit for that point before the installation is carried out.
Running current limits: HDB caps the maximum total running current at 5.00amps for 1- and 2-room flats, and 8.50amps for 3-, 4- and 5-room flats, Executive Maisonettes, Multi-Generation flats and 4-bedroom Executive Apartments (11.00amps for 5-bedroom Executive Apartments in converted blocks). The maximum condensing unit weight is 80kg.
Flats with a 40amps main switch, or upgraded under MUP or HIP:
No permit: installation does not need a permit, whether you use an existing or a new 15amps power point or 20amps isolator, but HDB's guidelines still apply.
Point rating: the aircon's running current should be restricted by a 20amps double pole (DP) isolator or 15amps power point.
Number of units: a maximum of 2 split-type condensing units can be installed.
Weight: the maximum is 110kg per wall panel, whether the unit sits on the external wall or the aircon ledge, and each wall panel can take only 1 wall-mounted condensing unit.
In every case, HDB says you and your installer must check that the total running current of your condensing units does not exceed the approved electrical rating before installation. If your block is due for HIP, our HDB HIP timing guide explains what to time around it.
Where the condenser and pipes can go
HDB's technical requirements shape the layout of your aircon system:
Approved location: the location and installation method of window units and split-type condensing units, including the condensed water discharge pipe, must follow the approved location and method. You can verify these with the HDB Branch managing your flat.
Ledge use: the aircon ledge is strictly for the condensing unit only.
Not in the corridor: condensing units cannot be located along the common corridor.
Pipes run inside: all aircon piping must run internally, and pipe joints must be insulated to prevent condensation and dripping.
Condensation water: it must be discharged properly into a nearby floor trap in your flat.
No hacking the structure: no holes or openings may be hacked through existing reinforced concrete structures in the flat, and aircon pipes must not be embedded in reinforced concrete slabs, columns or beams.
Tiled pre-cast facades: a single 50mm x 50mm opening per panel is allowed for the refrigerant pipe. The installer should check the surrounding wall tiles for bolts and refrigerant pipes, and any delaminated tiles have to be removed.
Vibration: condensing units must not cause vibration in the building, and rubber padding should be provided at the base of the unit.
Gas pipes: if you want a condensing unit in a living room where an existing gas pipe passes through, you must engage a licensed gas service technician to check the gas pipes and installation against Code of Practice CP 51 first.
Because the pipes must run inside the flat and cannot be embedded in the structure, the route usually runs along walls and ceilings in trunking or behind carpentry and false ceilings. Our aircon trunking design guide covers how to plan those routes so they look neat.
Keeping the ledge and supports safe
HDB and the Town Council set conditions for flats with a unit on the aircon ledge: do not tamper with the ledge, keep it clean and free of obstruction at all times, and give HDB, the Town Council and other authorities access to check the ledge if needed. HDB also asks owners to keep the external wall free from stains, maintain the aircon regularly so it does not cause nuisance to neighbours, and attend to any nuisance when it arises. Otherwise, HDB may ask you to stop using or remove the unit.
BCA advises owners to inspect aircon supports such as stainless steel brackets and concrete ledges for corrosion or damage at least every 6 months, have a trained installer inspect them during routine servicing, replace badly corroded brackets with new stainless steel ones, and repair cracks in concrete ledges. Units installed outside or projecting from a building must be supported by a stainless steel bracket or a concrete ledge or casing designed for the purpose.
A simple aircon checklist for your renovation
Check your main switch: confirm whether your flat has a 30amps or 40amps main switch, and whether a new point needs a permit
Size the system: check the total running current, number of condensing units and weight against HDB's limits for your flat
Confirm the installer: ask for the BCA trained installer's identification pass and check the BCA list
Agree the routes early: plan piping, trunking and the condensation discharge to a floor trap before carpentry and false ceilings are fixed
Keep the ledge clear: use it only for the condensing unit, and do not store anything there
Keep the paperwork: make sure the installation report is submitted within 14 days, and test every unit before your final payment using our renovation handover checklist
Planning other works at the same time? Our HDB renovation permit guide explains what needs approval, and our HDB renovation hours guide covers working hours and neighbour notices.
Where Blackwoods Interior stands
Blackwoods Interior Pte. Ltd. (trading as Blackwoods Interior), UEN 201909521M
CaseTrust accredited for Renovation Businesses (the standard tier, not Gold), valid through 28 April 2028
Listed on HDB's Directory of Renovation Contractors (DRC)
Talk to Blackwoods Interior
Planning new aircon or trunking as part of your renovation? Book a free 30-minute consultation: WhatsApp us at 8754 3212 (Mon-Sat, about 10:00-19:00 SGT) or email Hello@bwi.sg. Visit www.bwi.sg to see more.
Cover image: illustrative concept, not a completed Blackwoods project. This guide is general information based on HDB's renovation guidelines for air conditioner installation works and BCA's air-conditioning safety page, checked on 27 October 2026. Rules can change, so check the latest requirements for your flat with HDB, and use a BCA trained installer, before you start any aircon works.
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