Aircon Isolator Switch Singapore: The 2026 LEW Guide
You bought a new aircon. The receipt says you need a 15A power point or a 20A isolator switch before the installer can mount the indoor unit. The aircon company quoted you for the aircon, but not the isolator — and now you have three days to sort it out.
Here is what an EMA-licensed electrical worker (LEW) actually does at that point, what the law in Singapore requires, what it should cost in 2026, and the small details that decide whether the job is done once or revisited inside a year.
What an aircon isolator switch actually is
An aircon isolator is a dedicated switch that sits between your distribution board (DB) and the aircon condenser. Its job is one thing: cut the power to the aircon fully and safely so that a technician can service or replace the unit without working on a live circuit.
It is not the same as a 13A wall socket. It is not the same as the on/off button on your remote. It is a hard isolation device, sized to the load of the aircon, with proper earthing and overcurrent protection upstream. Without one, any future aircon servicing is either unsafe or non-compliant — and most aircon servicing firms will refuse to start work.
The short version of the law
Under the Electricity Act (Cap. 89A), any new fixed wiring or addition to your electrical installation in Singapore must be carried out or supervised by an EMA-Licensed Electrical Worker. That includes the aircon isolator and the cable that feeds it.
A few practical points fall out of this:
- The aircon installer is usually a BCA-trained aircon technician, not a Licensed Electrical Worker. They are allowed to connect to an existing isolator that an LEW has installed. They are not allowed to install or move the isolator themselves.
- New work on an HDB flat with a 30A main switch requires an HDB permit before an LEW does the installation.
- New work on a flat with a 40A main switch (most newer blocks and units upgraded under MUP) does not need a permit, but the LEW still has to test the installation and submit Form CS/5H to SP Services so the new circuit is on record.
- All installations should comply with SS 638:2018, which replaced SS CP 5 from 15 November 2020. If a quote you have received still references CP 5, the contractor is working off an outdated reference.
That last point matters more than it sounds. A correctly installed aircon isolator in 2026 is sized, protected, and tested against SS 638:2018 — not a standard that was retired six years ago.
15A point, 20A isolator, 32A isolator — which one do you actually need?
This is the single most common question we get on WhatsApp before a site visit. The answer comes from the aircon’s nameplate, not from the aircon brand.
The rule is simple: the isolator (or power point) rating must safely handle the maximum running current plus the starting inrush of the compressor. In Singapore, that maps cleanly to system size for most domestic aircons:
| Aircon system | Typical full-load current | Recommended isolation |
| System 1 (single split, 9k–12k BTU) | Under 13A | 15A power point on a dedicated 20A circuit |
| System 2 (12k–18k BTU per unit) | 8A–13A per indoor | 20A double-pole isolator |
| System 3 (multi-split, common 24k–28k BTU outdoor) | 13A–20A | 20A double-pole isolator |
| System 4–5 (multi-split, 30k BTU and above) | 20A–28A | 32A double-pole isolator, sometimes on its own sub-DB |
| Aircon system | Typical full-load current | Recommended isolation |
| System 1 (single split, 9k–12k BTU) | Under 13A | 15A power point on a dedicated 20A circuit |
| System 2 (12k–18k BTU per unit) | 8A–13A per indoor | 20A double-pole isolator |
| System 3 (multi-split, common 24k–28k BTU outdoor) | 13A–20A | 20A double-pole isolator |
| System 4–5 (multi-split, 30k BTU and above) | 20A–28A | 32A double-pole isolator, sometimes on its own sub-DB |
Two things go wrong when this is sized incorrectly:
- An undersized isolator overheats. You will smell warm plastic from the unit on hot afternoons, and eventually the contacts will pit and burn.
- An oversized isolator with an undersized upstream cable defeats the safety. The cable will overheat long before the isolator trips. This is one of the more common causes of concealed-cable fires we are called to investigate.
If you do not know your aircon’s BTU or running current, send the model number to your electrician on WhatsApp before the site visit. We can look up the nameplate and size the circuit before we step into your home.
The HDB rules in plain English
If you live in an HDB flat, you are working inside HDB’s electrical works framework. Here is what that means in practice for an aircon isolator:
Flats with a 30A main switch (older flats not yet upgraded): A new 15A power point or 20A isolator for aircon use needs an HDB permit. Your LEW submits the permit. After the work is completed and tested, you submit Form CS/5H, endorsed by your LEW, to SP Services to energize the new circuit.
Flats with a 40A main switch (newer blocks, MUP-upgraded flats): You do not need an HDB permit to add a 15A power point or 20A isolator for aircon. Your LEW still has to test the installation and submit Form CS/5H so the new circuit is on record with SP Services.
Wiring concealment: HDB does not allow new wiring to be embedded in RC slabs, beams, columns, walls, or wall plaster. Your LEW will surface-mount the cable in PVC trunking or run it through the ceiling void / above the false ceiling. If a contractor is offering to chase the wall and bury the cable, they are quoting work that HDB will not approve.
If your HDB flat has a 30A main and you are upgrading more than one aircon point — say, replacing all four split units after a renovation — it is often worth assessing whether the main switch should be upgraded to 40A at the same time. That is the kind of judgment call that belongs on an HDB electrical works assessment, not a phone quote.
Condo and landed: different building, same physics
Condominium: Most condos route aircon circuits in concrete soffits or floor slabs. Adding or relocating an isolator means tracing the existing circuit with a cable detector and either reusing the concealed cable or running new in trunking along the slab edge. MCST notification is usually required. The MCST may ask to see the LEW’s license number before any work starts in the unit.
For larger condo units with multiple aircon points, we sometimes consolidate them onto a dedicated aircon sub-DB. This avoids nuisance tripping when several compressors start at once. More on that in our condo electrical services page.
Landed: Landed properties almost always run on a three-phase supply. An aircon isolator on the wrong phase can put a leg of the supply under heavy load while the other two run light, causing the main DB to heat and the breakers to trip on warm evenings. The fix is to properly balance load across L1, L2, and L3 at the DB design stage.
If you are doing a full landed renovation, the aircon circuits should be planned with the rest of the load — pool pump, EV charger, induction hob, water heaters, and gate motor. We cover that on our landed house electrical works page, and if the existing supply is not coping, you may need a 3-phase power upgrade.
What the aircon company will not put in their quote
Two things are typically excluded from the aircon installation quote, and both are LEW work:
- The isolator itself, with its dedicated circuit and earthing. The aircon company will quote bracket, piping, gas, and labor. They will note “15A power point required” or “20A isolator required” on the invoice and leave the electrical work to you.
- The wiring runs from your DB to the isolator location. This is the part most homeowners underestimate. A 20A circuit from your DB to a balcony or service yard is a real cable pull — usually 15 to 25 meters of 4mm² flexible cable, in trunking, with proper bends and terminations.
When we quote, both of those are itemized: isolator unit, cable, trunking, breaker (or RCBO) at the DB, labor, and the SP Services Form CS/5H testing fee, where applicable. That is also why a fair LEW quote for an aircon isolator in Singapore lands in the $250–$650 band rather than the $80–$120 figure you sometimes see for “isolator replacement” — the latter is swapping the switch on an existing circuit, not building a new one.
Cable, breaker, and RCD — the parts most quotes leave vague
Under SS 638:2018, Chapter 53 covers isolation and switching, and the protective device upstream of the isolator has two jobs: protect the cable against overload, and protect the user against an earth fault.
For a domestic aircon installation in Singapore, that usually means:
- Cable: 2.5mm² flexible PVC for a 15A point or small System 1; 4mm² for a 20A isolator and most System 2 and System 3; 6mm² for a 32A isolator on a larger multi-split. Always with a properly bonded earth conductor.
- Upstream device: 20A or 32A MCB at the DB, paired with the RCCB on the existing socket-outlet bank, or — better — a dedicated 20A/32A RCBO so the aircon has its own earth-fault protection. SS 638:2018 mandates 30 mA residual current protection for domestic sockets and lighting circuits, and we apply the same logic to the aircon circuit even though the rule is technically about sockets.
- Isolator: Double-pole, rated to match the MCB/RCBO. For 20A, double-pole 20A. For 32A, double-pole 32A. Outdoor-mounted isolators near the condenser must be IP-rated (typically IP55) for weather exposure.
If your quote does not mention cable size, MCB or RCBO rating, and isolator pole count, it was written by someone who has not yet planned the circuit. That is the moment to ask for a proper itemized version.
Aircon isolator cost in Singapore — what you should expect to pay in 2026
These are indicative ranges for properly itemized, EMA-licensed work, including the isolator unit, cable, trunking, breaker, and SP Services testing where applicable. The final price always depends on the cable run length, the property type, and whether there is an existing DB slot or one needs to be made.
| Scope | Indicative range (SGD) |
|---|---|
| New 15A power point for System 1 aircon (HDB, short run) | $250 – $350 |
| 20A double-pole isolator (single-split or System 2, HDB or condo) | $350 – $500 |
| 32A double-pole isolator (System 3+ multi-split) | $450 – $600 |
| Dedicated aircon sub-DB with 2–3 isolators (landed or large condo) | $550 – $650+ |
| HDB permit submission and Form CS/5H testing | Usually included in the above |
For a full breakdown of electrician rates in Singapore across all common jobs, see our 2026 electrician price guide.
Five things that go wrong (so you know what to ask)
These are the five issues we see most often when called back to fix someone else’s aircon isolator work:
- Undersized cable on an oversized breaker. A 4mm² cable on a 32A breaker will overheat well before the breaker trips. We redo these every month.
- No dedicated earth. The isolator earth is taken from the nearest socket outlet’s earth instead of being pulled fresh from the DB. Looks fine at testing, fails when there is a real fault.
- No RCD/RCBO protection. Compressors fail to earth occasionally. Without 30 mA residual current protection, that fault poses a shock risk whenever someone touches the condenser casing in the rain.
- Indoor-rated isolator on an outdoor wall. A standard surface-mount isolator without an IP rating will corrode at the contacts within 12–18 months in Singapore’s humidity, especially on a west-facing wall.
- No Form CS/5H submission. Work is done, isolator is installed, and no one tells SP Services. When you sell the flat, the buyer’s lawyer flags an unregistered circuit, and the sale gets messy. Easy to prevent during installation.
If you have an existing isolator that ticks any of those boxes, you can send us a photo over WhatsApp, and we will tell you straight whether it needs to be redone. Sometimes it does not. Sometimes a $30 fix prevents a $300 repair later. We will not push work that does not need to be done.
How to verify the electrician before you book
Three checks, one minute each.
- Ask for the EMA Licensed Electrical Worker number. A valid LEW has a license card with their photo and a number. You can verify the number on the EMA ELISE portal.
- Ask for the company UEN. A licensed electrical contractor in Singapore has a UEN. Ours is 202302469E.
- Ask whether they will submit Form CS/5H for new circuits. If the answer is “we don’t normally do that” or “you don’t really need it for one isolator,” that is a contractor who will leave you with an unregistered circuit.
If those answers come back clean, the rest is just price and timing.
Frequently asked questions
Can the aircon installer install the isolator switch themselves?
No. Under Singapore’s Electricity Act, the installation of new fixed wiring, including the isolator and its supply cable, must be carried out or supervised by an EMA-Licensed Electrical Worker (LEW). Aircon installers are BCA-trained for aircon work and may connect the aircon to an isolator already installed by the LEW, but they cannot install or relocate the isolator themselves.
Do I need a 15A power point or a 20A isolator for my aircon?
A 15A power point is enough for a single System 1 (9k–12k BTU) where the aircon’s running current is below 13A. A 20A double-pole isolator is the correct choice for System 2 and most System 3 setups. System 4 and System 5 multi-splits typically need a 32A double-pole isolator. The deciding factor is the aircon’s nameplate, not the brand.
How much does it cost to install an aircon isolator switch in Singapore in 2026?
Indicative ranges: $250–$350 for a 15A power point installation, $350–$500 for a 20A double-pole isolator, $450–$600 for a 32A isolator, and $550–$650+ for a dedicated aircon sub-DB with multiple isolators. Final price depends on cable run length, property type, and whether your DB has a free slot.
Do I need an HDB permit for an aircon isolator?
You need an HDB permit if your flat has a 30A main switch (typical of older blocks not yet upgraded). If your flat has a 40A main switch — most newer blocks and flats upgraded under the Main Upgrading Program — no permit is needed for a new 15A point or 20A isolator for aircon use. In both cases, your LEW must test the installation and submit Form CS/5H to SP Services.
Where should the aircon isolator be installed?
Outdoor isolators are usually mounted on the wall next to the condenser unit, at a height that an aircon technician can reach without a ladder. They must be IP55-rated for weather exposure. Indoor isolators are sometimes installed for fan-coil units in service yards or on balconies. The location should allow the aircon to be fully isolated for servicing without needing to trip the main DB.
Can I reuse the old isolator when I replace my aircon?
Sometimes. If the old isolator is correctly sized for the new aircon, is in good condition (no corrosion, no warm spots, no loose terminals), and was originally installed by a Licensed Electrical Worker on a properly sized circuit, it can be reused. An LEW should still test the circuit and the isolator’s contacts before reconnecting. If the new aircon is larger than the old one, the isolator and circuit may need to be upgraded.
What is the difference between an isolator switch and a circuit breaker?
A circuit breaker (MCB or RCBO) at your DB protects the cable against overload and earth fault. It is meant to trip automatically when something goes wrong. An isolator is a manual switch near the equipment that disconnects the supply for maintenance. They are not interchangeable. A correctly designed aircon circuit has both: a breaker upstream at the DB and an isolator next to the condenser.
Is one isolator enough for two aircon units?
No. Each aircon should have its own isolator on its own dedicated circuit. Sharing an isolator across two aircons means servicing one unit cuts power to the other, and the circuit must be sized for both compressors starting together, which usually means an upsized cable and breaker. It is almost always cheaper and always safer to give each aircon its own isolator.
What is SS 638, and why does it matter for my aircon installation?
SS 638:2018 is Singapore’s current Standard for low-voltage electrical installations. It replaced SS CP 5 from 15 November 2020. Aircon isolator installations done in 2026 should comply with SS 638:2018, particularly Chapter 53 on protection, isolation, and switching. If a quote you have received still references CP 5, the contractor is working off a retired standard.
How long does the installation take?
A single 20A isolator installation in an HDB flat typically takes 2–4 hours from arrival to testing, assuming a free DB slot and a reasonable cable run. A 32A isolator with a longer cable run can take 4–6 hours. A new sub-DB with multiple isolators on a landed property usually takes a full day. We give you a target window before we start.
Ready to get your aircon isolator done properly?
If your aircon is being installed this week and the installer has told you to sort out the 15A point or 20A isolator first, WhatsApp us the aircon model number and a photo of your DB box. We will come back with a sized circuit, a fixed price, and a slot — usually same day or next.
Quote upfront. EMA-licensed. Form CS/5H submitted to SP Services. 90-day workmanship warranty.
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