Aircond circuits in Malaysia: breaker and cable size, hot or melting switches, and how many units single-phase can run

For a normal split aircond under 3HP, the Energy Commission’s (ST) wiring guideline points to its own circuit from the DB, 4mm² cable, a 20A MCB, and a double-pole switch, socket or isolator next to the unit. The reasoned answers in Malaysian wiring groups mostly agree, although plenty of wiremen still run 2.5mm² for units up to 2HP to keep the price down. The breaker is there to protect the cable, so it isn’t made bigger because the aircond is bigger. And if the aircond switch is getting hot or keeps melting, the switch is usually the victim. The cause is a loose terminal or a cable that’s too thin.

The rest of this page goes question by question. It’s built from discussions and job reports in Malaysian electrical Facebook groups during 2026, checked against ST’s guideline, TNB’s supply rules and manufacturers’ Malaysian spec sheets.

The short answer by size

The currents come from Daikin, Panasonic and Mitsubishi Electric Malaysian spec sheets for inverter and non-inverter wall units. Some brands print much higher figures: Midea’s Malaysian manuals list 14–19.4A for its 2–2.5HP units, which look like maximum ratings. Your unit’s own label is what counts (next section).

The rule behind the middle column is ST’s domestic wiring guideline:

• Its own circuit. Aircond, water heaters, ovens and dryers must each be on a circuit separate from everything else (clause 9.1(g)).
• Cable size. The minimum-size table (Table 8.2) lists 4–6mm² for “special power circuits”, aircond included.
• Example board. Its sample single-phase DB wires “split unit under 3HP” with 2 × 4mm² plus earth on a 20A breaker.
• Connection point. The aircond can’t be wired straight into the circuit. It connects through a switch, a 13A or 15A socket outlet, or an isolator fed from a suitably rated breaker, so it can be isolated for servicing or in an emergency. Units above 3HP must be fixed-wired to a suitably rated breaker (clause 9.1(m)).

ST calls its sample boards “guidance only”. So treat 4mm²/20A as the reference spec, not the only legal combination.

Reading the label: running current vs maximum current

People often work out an aircond’s current from its horsepower. That goes wrong because aircond “HP” is shorthand for cooling capacity (9,000 Btu/h is sold as 1HP, 18,000 as 2HP). It isn’t the electrical input. Read the nameplate on the side of the indoor or outdoor unit instead:

• Rated or running current: what it draws in normal cooling. One Electrolux label posted in a wiring group shows 8.3A at 1,863W. The most-liked technical reply divided 1,863W by 746 and called it a 2.5HP, which is wrong: it’s an 18,500 Btu/h unit, sold as 2HP.
• Maximum (rated) current: the worst case. On that Electrolux it’s 15A. Midea’s Malaysian manual says the supply cable, fuse and switch should be sized from the maximum current on the nameplate. With 15A maximum, most replies landed on a 20A MCB, which matches ST’s example.
• Start-up current: the short surge when a non-inverter compressor starts. Older Acson Malaysia technical manuals list 18A, 24.5A and 32A for 1, 1.5 and 2HP non-inverter units that run at about 4–8A, so four to five times the running current for a moment. ST’s guideline says a breaker protecting a motor circuit must handle the motor’s starting current without tripping. The “C” in C16 or C20 is the trip curve: a C-type MCB only trips instantly at 5–10 times its rating, so a short start-up surge doesn’t trip it, while a sustained overload still does. That’s the type Malaysian home DBs normally use.

A small inverter really does draw little. One 1HP inverter label shows 3.3A at 745W, less than a kettle. That matters later, when a plug burns.

Daikin’s and Panasonic’s current wall units take their power at the indoor unit, so the switch or socket goes beside the indoor unit, and the indoor-to-outdoor cable is the installer’s job. Some larger units take it at the outdoor unit; Panasonic’s 30,000 Btu/h non-inverter is one. That’s where outdoor isolators come in.

2.5HP on a C16 or C20?

This was the most-reacted-to aircond question in the groups this year: a dedicated circuit, 4mm² live and neutral, a 2.5mm² earth, and a C16 already in the DB. More than 150 replies split three ways.

• C20 (the largest group). The C20 camp’s best-liked reply (33 reactions) pointed to start-up: the current is high for one to three seconds when the compressor kicks in, so a C16 is cutting it close. In a similar thread about a 2.5HP, the best-liked answers were “ikut Suruhanjaya Tenaga guna cable 4mm² … mcb guna C20” and “cable 4mm, mcb 20a”. That’s also ST’s example.
• C16 works. The most-liked single answer (61 reactions) said the MCB’s job is to protect the cable, so a 16A breaker on 4mm² is fine, provided it can take the unit’s starting current. Another reply suggested keeping the C16 and changing to C20 only if it trips. That’s reasonable for an inverter unit whose label shows a low maximum current. With a non-inverter, or a label like Midea’s with a high maximum, go straight to C20.
• C32 (a vocal minority). Several said 32A “for the long term”. Others rebutted them hard: a bigger breaker doesn’t give the aircond more power. It only lets the cable carry more before tripping. ST’s table for socket circuits puts 4mm² radials on a 30 or 32A breaker, so 32A on 4mm² isn’t unsafe for the cable, but it’s far above what a home split unit draws. On 2.5mm² a 32A MCB is wrong for a single aircond or heater circuit, and every thread that raised it said so. In the same table, 2.5mm² radials get 20A; the 32A-on-2.5mm² combination is for a ring circuit of sockets, which is a different arrangement.

The poster’s 2.5mm² earth deserves a note too. ST’s protective-conductor table makes the earth the same size as the live conductor up to 16mm², unless a designer calculates otherwise. Two replies made the same point: with 4mm² live and neutral, use a 4mm² earth.

2.5mm², 4mm² or 6mm²?

This is the biggest gap between the book and the trade:

• ST’s table says 4–6mm² for aircond circuits.
• Many wiremen and price lists use 2.5mm² for units up to 2HP and 4mm² above that. One Johor contractor’s 2026 price list states it outright: aircond up to 2HP “menggunakan 2.5mm yg diluluskan oleh SIRIM” (use SIRIM-approved 2.5mm). Older Acson Malaysia manuals recommended 1.5mm² with a 15A fuse for 1–1.5HP and 2.5mm² with 20A for 2–3HP. Those are the manufacturer’s minimums for the unit, not ST’s fixed-wiring minimum.
• 6mm² comes up for long runs from the DB, units that run all day, and kampung areas where the voltage sags under load. Others call it a waste for a normal room.

Why the split? Current inverter units draw less than the old non-inverters, and 2.5mm² is cheaper and easier to pull. In the 2026 price threads, the same wireman’s 2.5mm² and 4mm² quotes for a point typically differed by RM100–250.

If you’re paying for a new point, ask for 4mm². It meets ST’s table, takes a bigger unit later without rewiring, and the quote should say which size you’re getting. A terrace-house owner in our wiring prices guide paid for three aircond points expecting 4mm² and found 2.5mm². Our SIRIM cable guide explains how to check the cable itself.

Which switch: 20A double-pole, 15A socket, 32A or 45A, or an outdoor isolator

• 20A double-pole (DP) switch, the “suis aircond / suis heater”. This is the standard choice. It breaks both live and neutral, has an earth terminal, and usually a red neon. Schneider’s Vivace 20A DP switch is rated to MS IEC 60669-1. Hager Malaysia even sells a 20A DP switch labelled “Air Conditioner”. The supply from the DB goes to the terminals marked LINE and the cable to the aircond to LOAD.
• 13A or 15A socket and plug. ST’s clause allows either. Many installers prefer a 15A socket and plug. A 13A plug is fine electrically for a small inverter, but it’s a weak spot on a continuous load if the contacts are worn (see below).
• 32A or 45A DP switch. Some wiremen fit these on 2.5HP and up because they think they “last longer”. There’s no rule requiring it. Schneider and Hager both sell 32A and 45A DP switches.
• Weatherproof outdoor isolator. Use one when the supply goes to the outdoor unit, or for cassettes and commercial units. Hager’s JG220U is a 20A two-pole IP66 isolator that takes 2.5–4mm² cable. The 32A version takes 6–10mm².
• A normal one-gang lighting switch. A 145-reaction post asked why not, since one had lasted two years. Replies: it’s single-pole, rated for lighting loads, and doesn’t isolate the neutral. “Pakai je 2 pole heater switch, bila off putus live & nuetral sekali.” Midea’s manual asks for an all-pole disconnect with at least 3mm contact gap.
• DOL starters. A DOL (direct-on-line) starter is a motor starter box with START and STOP buttons, once common on bigger aircond units. ST’s guideline requires DOL starters for motors of 0.5–3HP except aircond motors. Group members disagree (“2HP and up needs DOL” vs “that’s from the old days”). A member of the KakiRepair group whose old starter-type box had failed asked whether a 20A heater switch could replace it. Since ST doesn’t require a DOL starter for an aircond, a DP switch on the unit’s own circuit meets the connection rule. For a surau planning eight 2.5–3HP units, wiremen suggested a panel with a contactor per unit, so they can all be controlled from one place.

Why an aircond switch gets hot or keeps melting

A warm switch plate isn’t normal. In a 90-comment thread about one, the top answer (40 reactions) put it in one line: “wire tak ketat, cable size tak cukup besar” (the wire isn’t tight, or the cable is too small). What the job reports and replies add:

• A loose or poorly made terminal. It gets worse on its own: the joint heats, the copper oxidises, the screw loosens further. One wireman’s advice: switch off at the MCB, cut back any blackened copper, re-terminate cleanly and tighten. Another pointed out that a screw tightened properly today can still work loose over the years.
• A cable that’s far too thin. A homeowner’s 2.5HP switch melted three times, with cheap and expensive switches alike. The cable turned out to be a three-core flex printed “110/0.076”. That’s about 0.5mm² per core, a third of a lighting cable. Replies said the switch was just the weakest point; the fix was new single-core 4mm² from the DB on its own MCB. Three-core flex looped from a nearby socket comes up again and again in these threads.
• A shared or looped circuit. Aircond, fridge and kitchen sockets on one MCB, or an aircond fed off the nearest socket. The cable and every joint on it carry more than intended.
• An old or worn switch. One reply described a switch nearly 20 years old that ran hot for a long time before the wiring inside burnt.
• A unit drawing more than it should. If a correctly wired point still overheats, a wireman or aircond technician should clamp-meter the running current. A failing compressor, low refrigerant or a filthy coil can push it well above the label. One owner traced repeated trips to a high-amp compressor and paid RM300 to replace it.

Burnt plugs follow the same logic. In the KakiRepair group, a 1HP inverter’s 13A plug and socket had burnt. The unit’s label shows 3.3A, so overload wasn’t the problem. A member’s follow-up post pointed to where the plug had burnt: the fuse wasn’t making good contact with its holder, and the resistance heated it. The annotated photo in that post puts it plainly: “This is poor connection, NOT excessive current draw.” Another member’s LG 1HP inverter melted its socket’s neutral terminal; the practical answer was to replace the plug and socket and tighten every terminal. In Bukit Naga, Shah Alam, a wireman rewired an inverter unit direct from the DB after its plug and socket charred and nearly caught fire. The rule allows a socket. What fails is a worn contact on a load that runs for hours, often on a shared socket circuit.

What you can safely do yourself: switch the aircond off at its MCB if the switch or plug is hot, browned, smells of burning or crackles, and don’t keep using it. Opening the switch, re-terminating and replacing cable is a wireman’s job. Our DB fire guide explains how the same loose-terminal heating starts fires in the DB itself.

Which RCCB protects an aircond?

ST’s guideline puts aircond circuits, with lighting and fans, under a residual-current device of 100mA or less. Socket circuits get 30mA or less and water heaters 10mA. Midea’s Malaysian manual asks for an RCD of 30mA or less where the unit is fixed-wired. Mitsubishi says to fit an earth-leakage breaker “depending on the installation location”, such as humid spots. So a typical board puts the aircond MCBs under the 100mA RCCB with the lights, or under the 30mA one with the sockets. On 30mA, expect more nuisance trips: compressors and their electronics leak a little, and an RCCB sees the total leakage of everything downstream. Our RCCB tripping guide covers finding which appliance is doing it.

Be careful with RCCB advice in the groups. The most-liked answer on this question this year (107 reactions) was a polished, AI-style reply that told a homeowner with water heaters that “water heater wajib 30mA”. ST’s guideline asks for 10mA on water-heater circuits, and members argued it out underneath (“Berhati-hati pakai AI”). ST’s table, linked above, is the reference. For heaters, see our water heater RCBO guide.

Several aircond units on one MCB

Don’t. Every thread where a homeowner found two or three aircond sockets on one breaker drew the same answer from almost everyone: “1 aircond 1 MCB”, with its own cable from the DB. ST’s clause 9.1(g) requires a separate circuit. Two 1HP units plus two fridges on one C20 also got a clear no. Each compressor has its own start-up surge, and a fridge runs all day. The fix is usually cheap if the DB has spare slots: one more MCB and a new cable run for each unit.

How many aircond units can a single-phase house run?

TNB’s upgrade page advises switching to three-phase when household load exceeds 10kW. It adds a blunt rule of thumb: “if you have three (3) or more air conditioners in your home, you should upgrade to a 3-phase supply”. TNB’s supply handbook caps single-phase supplies at 12kVA maximum demand.

Wiremen treat the three-unit rule as conservative, and so does our single vs three-phase guide. In a 100-comment thread on exactly this question, owners reported running four to seven units on single-phase without trouble, such as two 2HP, one 1.5HP and four 1HP all on together. Others told of a friend’s house whose cut-out burnt three times with five units on single-phase. What decides it is the current while everything is on:

• Add up the running currents from the labels. For a 3HP, a 2HP and three 1HP, commenters’ estimates ran from about 25A to 40A, before the fridge, water heater and rice cooker. Inverter units, once the room is cool, draw much less.
• Measure it. The best-liked advice (50 reactions) was to clamp-meter the incoming cable at the DB with every aircond and the usual appliances on. Replies put the comfortable limit around 40A, and said to consider three-phase as it nears 50A on a 60–63A supply.
• Stagger the starts. Switching units on a few minutes apart avoids stacking the start-up surges.
• Check the main switch and submain. In one thread, five non-inverter units kept blowing a house’s 32A main-switch fuse. The top reply said to replace it with a 63A two-pole MCB main switch. Others added the condition: only if the cable from the meter to the DB (the submain) is 16mm². With 10mm², the cable has to be changed first. That matches ST’s table: 10mm² for a main breaker up to 40A, 16mm² up to 63A.

Three-phase doesn’t make electricity cheaper; it spreads the load. Owners with four units reported monthly bills anywhere from about RM120 to RM800, depending on hours, setpoint and whether the units are inverters. On cost, one 2026 quotation for a new double-storey terrace priced the three-phase items (main and sub DB, cables, meter board and TNB submission) at about RM3,300. An owner who went to ten units paid RM9,000 for the three-phase work. TNB’s own worked examples put its connection charge for upgrading from single-phase at RM300 (overhead) to RM1,250 (underground). The three-phase guide covers the process and typical totals.

Adding an aircond point, including in a rental house

The usual job is a new MCB in a free DB slot plus a new cable run to a DP switch or socket by the unit. A full DB replacement is only needed if the board is full, damaged or unsafe. Our DB upgrade guide has examples where installers pushed a new DB that wiremen thought unnecessary.

When a renter posted their DB asking what to add for one aircond, the first answer was simply “add an MCB and run one point”. Then wiremen spotted DC-rated MCBs fitted on AC circuits, a lighting circuit on an oversized breaker and an old breaker range they distrust. That board needed fixing first. A three-storey terrace owner with one small DB, planning two 1.5HP units, was told to have the board upgraded before adding them. In a rental, the DB and wiring belong to the landlord, so that conversation comes before anyone drills.

Looping an aircond off the nearest socket (“jimat kos”) still gets suggested for rentals, and wiremen reject it for the reasons above.

Moving the aircond switch

A Kuala Lumpur (Pandan Indah) homeowner asked in May 2026 what it costs to move an aircond switch about 1.2m and bury the wiring. More than 200 comments followed. Offers clustered around RM150–300, with one RM200 quote including closing the old hole and skimming the wall. Outliers ran from RM100 to RM600.

Most replies talked about something else: the indoor unit was jammed against a newly built boxed-in ceiling section, so it couldn’t breathe or have its filter removed. If you’re moving a switch because of renovation work, check that the unit still has clearance above and room to service. One wireman also warned against putting the switch directly under the indoor unit, where condensate can drip on it.

What it costs (2026 quotes and ads)

For a new aircond point from the DB, including cable, switch or socket, and labour:

Concealed runs (hacking and plastering), long distances and 4mm² push prices up. The cheapest ads often assume a short run or 2.5mm² cable, so check what’s included. Quotes far below the pack usually mean thinner cable, a loop from the nearest socket or a surface run with no casing; one reply in the March thread described a RM100 point as exactly that. Adding a single MCB to a DB with a spare slot was quoted at about RM35–60. For other point rates, see our house wiring prices guide.

What you can check yourself, and what needs a wireman

You can read the nameplate’s running and maximum current, look at the DB to see whether the aircond has its own MCB and what rating it is, and feel whether a switch plate or plug is warm. Switch off at the MCB if anything is hot, browned or smells. You can also ask a quote to state the cable size, MCB rating, switch type and whether the run comes direct from the DB.

Opening switches, adding MCBs, running cable, changing the main switch or upgrading to three-phase are wireman’s work, and the TNB side (cut-out and meter) is TNB’s. Our Johor Bahru electricians guide shows where local wiremen advertise. For buying the unit itself, energy labels and installation quality, see our aircond buying and installation guide. For choosing breaker brands, see MCB and RCCB brands.