Water heater RCBO or RCCB in Malaysia: 10mA, the right amp rating and cable size

If you’re installing or checking a shower water heater in Malaysia, the short version is this: the heater needs its own circuit from the DB, protected by an RCD that trips at 10mA or less, with an overcurrent rating that matches the heater’s power and 4mm² cable for ordinary home heaters. An RCBO does both jobs in one unit; an RCCB plus an MCB does the same thing in two. A 30mA RCCB covering the whole house, an MCB on its own, or the little leakage switch built into the heater doesn’t meet the rule.

That’s not a wireman’s preference. It comes from the Energy Commission (Suruhanjaya Tenaga, ST), and it’s also where experienced electricians in Malaysian wiring groups land almost every time the question comes up — which is often. Homeowners post photos of RCBOs, contractors’ quotes and tripping breakers asking the same handful of questions, and the confident answers aren’t always right: long replies claiming “30mA is still allowed” get plenty of likes before other members point out they contradict the regulation.

What the rules say

Regulation 36 of the Electricity Regulations 1994 sets earth-leakage protection by location. Where the floor is likely to be wet, or walls and enclosures have low resistance, circuits must be protected by a residual current device rated not more than 10mA. Circuits for hand-held appliances (in practice, socket circuits) get 30mA, and everything else 100mA. A bathroom with a shower heater is the textbook wet location.

ST’s water heater guideline (GP/ST/No.6/2016) spells out the circuit:

• a dedicated circuit from the distribution board, used for nothing else;
• an MCB and an RCD in series, with the RCD at 10mA or less — and it says outright that MCB–RCD combinations such as RCBOs are acceptable;
• a two-pole RCD on single-phase supply, so it disconnects both live and neutral, plus a two-pole isolator or switch near the heater; the earth conductor is never switched;
• a fixed connection: no 13A or 15A plug and socket, and an IPX5 connection box if the joint is inside the shower cubicle or below the ceiling;
• a non-metallic hose (not metal or chrome) to the shower head;
• a voltage-drop check, and thicker cable if needed, when the circuit runs more than 50 metres from the DB.

The domestic wiring guide, Garis Panduan Pendawaian Elektrik Pepasangan Domestik, repeats the 10mA requirement for heater circuits and adds that any RCCB or RCBO you use must be ST-approved and carry the ST-SIRIM label. Old voltage-operated ELCBs aren’t allowed at all. Storage heaters also need a working pressure relief valve.

The reason for the strictness is grim. A 2015 safety briefing hosted by ST lists seven reported electrocution deaths involving water heaters between 2009 and 2015, from a SIRIM working-group record. In most of them the house’s main RCCB wasn’t working, one involved undersized cables that had melted, and in every case the victim was still holding a metal shower head — which is why the non-metallic hose rule exists.

Reading the label: 10mA, 0.1s and 20A are different things

A lot of confusion in the groups is just label-reading. On a typical RCBO marked C20, 10mA (0.01A), t ≤ 0.1s:

• 10mA or 0.01A is the sensitivity — how much current leaking to earth it takes to trip. This is the number the rule cares about. 0.01A and 10mA are the same value.
• t ≤ 0.1s is a trip-time marking, not a sensitivity. A 10mA device marked 0.1s is still a 10mA device. Don’t mistake it for 0.1A, which would be 100mA.
• C20 works like an ordinary MCB marking: 20 is the rated current (the overload setting) and C is the trip curve, which sets how much short-circuit current trips it instantly. A “10A” in a quote or message is often a mix-up for 10mA.

If you want the general background on sensitivity, types and poles, our RCCB guide covers it; the MCB guide explains curves and ratings.

Matching the amp rating and cable to your heater

The overcurrent rating should follow the heater’s power. ST’s guideline gives a minimum device rating and cable size for each band at 230V:

So a typical 3.5kW unit needs at least a 20A device and a 4kW-ish heater at least 25A. Going below the minimum just causes overload trips. Going above it is allowed as long as the cable can carry it — the domestic guide itself mentions 20A or 32A protection for heater circuits — and the hard limit is that the breaker must never be rated above what the cable can safely carry. In practice, electricians in the groups prefer to match the heater: C20 or C25 for most home units, with C32 for higher-power heaters. When someone posts a C32 RCBO bought for a small heater, the usual reply is that it’s bigger than it needs to be.

Notice the cable column. Even the smallest heaters start at 4mm². Plenty of older and cheaper installations use 2.5mm², and you’ll still find wiremen defending it — “it’s worked for decades” or “Mega 2.5mm has thick copper”. Others insist 4mm² is compulsory. On paper the guideline settles it. If an existing 2.5mm² run works, it’s still below the current spec, and it’s worth knowing that before you accept a new installation.

“It keeps tripping, so I’ll use 30mA”

This is the other recurring argument, and the experienced answer is consistent: a 10mA device that trips regularly is telling you something is leaking. Common culprits are a failing heater element, water getting into a connection, or a neutral that’s shared or looped with another circuit. Electricians suggest having a competent electrician do an insulation-resistance test, connecting the heater’s neutral directly to the RCD’s own outgoing terminal (not a shared neutral bar), and checking the heater itself. Swapping to 30mA to stop the trips removes the protection you were trying to get.

The same goes for heaters with a built-in leakage switch. Many units have one, and some newer DC instant heaters advertise electronic earth-leakage sensing. It protects from the heater onward. It doesn’t protect the cable from your DB, and it doesn’t replace the 10mA device at the board.

RCBO or RCCB + MCB?

Both are allowed. An RCBO is one module doing overload and leakage protection; an RCCB + MCB pair uses a 2-pole 10mA RCCB (typically 25A) with a C20 or similar MCB feeding the heater. Electricians who prefer the pair say a proper two-pole 10mA RCBO is harder to find than the cheap compact ones, and that a separate RCCB tells you at a glance whether a trip was leakage or overload.

Two technical points come up whichever route you take:

• Type A versus Type AC. Type AC detects ordinary AC leakage. Type A also detects pulsating DC leakage that electronics can produce. ST’s domestic guide encourages Type A where there’s a lot of electronic equipment (and Type B or F where inverter equipment is used) but doesn’t make it compulsory for heaters. Several electricians recommend Type A for heaters with electronic controls or DC pumps. Most cheap marketplace listings “for water heaters” are Type AC, but Type A 10mA devices are in Malaysian catalogues (below); expect to pay roughly twice as much.
• Voltage dependence and poles. Several electricians warn that many compact RCBOs are voltage-dependent (VD) designs, which may not trip if the neutral is lost, and recommend a voltage-independent (VI) device instead. It’s hard to tell from the front: if the datasheet lists IEC 61009-2-2 (RCBO) or IEC 61008-2-2 (RCCB), it’s voltage-dependent; IEC 61009-2-1, IEC 61008-2-1 or an explicit “voltage independent” statement means VI; a datasheet citing only IEC 61009-1 or 61008-1 doesn’t settle it. Many 10mA RCBOs are also 1P+N (sold as “2P” or “1L+1N”), so if you need to show the 2-pole RCD the water-heater guideline asks for, ask the supplier how the neutral is switched. ST’s guidelines don’t distinguish VD from VI; electricians who say VD devices are prohibited in homes point to MS 1979, the residential wiring code those guidelines refer to.

Which 10mA devices are listed in Malaysia

From the manufacturers’ Malaysian lists and catalogues we’ve researched:

• Maxguard ML32-1 RCBO: 6–32A, B and C curve, 10mA in Type AC and Type A; its catalogue cites the voltage-dependent RCBO standard.
• Maxguard ML63-1 RCCB E25201N: 2-pole 25A 10mA Type AC, designed to the voltage-independent RCCB standard.
• Hager RCCBs: four 2-pole 10mA RCCBs — CC216B (16A) and CC225B (25A) in Type AC, CCA225B (25A) and CCA540D (40A) in Type A. Only CCA540D’s documents name the voltage-independent standard. Hager Malaysia’s current RCBO list has no 10mA model; its 10mA RCBO pages are marked spare part or obsolete.
• Schneider Easy9 RCBO: 25A and 32A, 10mA Type A, 1P+N; its datasheet cites the voltage-dependent standard.
• Schneider Easy9 RCCB and Acti9 iID: 2-pole 10mA RCCBs at 16–25A, in Type AC and (EZ9R26225, A9R20225, A9R30225) Type A; their Malaysian pages don’t state voltage dependence.
• Schneider Acti9 iDPN Vigi: voltage-independent 10mA Type A RCBOs, but only at 10A and 16A, so only for heaters under about 2.86kW.
• Schneider Vigi iC60 A9V10225 on a 2-pole iC60 MCB: Schneider’s one RCBO-type combination whose pages state 2-pole, voltage-independent and 10mA together; it’s Type AC and costs several times more.

A 25A device covers heaters up to about 4.46kW. For 4.46–5.71kW you need 32A, which on these lists means the Easy9 RCBO EZ9D16632, a 32A Maxguard ML32-1, or Hager’s 40A CCA540D RCCB with a C32 MCB.

Brands and what it costs

Brand arguments are lively but not very conclusive. Schneider, Hager and ABB get the most praise for build quality. Maxguard and EPS are widely installed budget brands, and opinion on Maxguard is split: some electricians use it without complaint, others call it a budget Type AC brand they wouldn’t choose for a home any more, although Maxguard’s own catalogue also lists Type A 10mA RCBOs. A few lesser-known names get dismissed outright. What actually matters for compliance is the rating, 10mA sensitivity and the ST-SIRIM label. If a wireman refuses a correctly rated, SIRIM-labelled RCBO only because it isn’t their preferred brand, that’s a preference, not the rule — although asking for Type A is a reasonable upgrade.

Prices in 2026 give a rough idea. A Type AC 10mA RCBO such as the Maxguard 20A sells for about RM66–103 across most Shopee and Lazada stores, and a Type A version for around RM169 (prices); group members reported paying RM50–80 at hardware shops. Check online listings carefully: members point out that some online-only brands don’t carry the ST-SIRIM label, and listings sold “for water heaters” sometimes turn out to be 30mA. One homeowner was charged RM80 extra for an RCBO instead of a plain MCB, and most electricians replying thought that was fair. One commenter quoted RM350 (EPS) or RM400 (Schneider) to fit RCBOs for two heaters. These are individual quotes rather than market rates, but they’re useful when a quote looks way off.

A quick checklist

• The heater has its own circuit from the DB, not a loop from a socket or light.
• There’s a 10mA (0.01A) RCBO, or a two-pole 10mA RCCB plus an MCB, on that circuit — and if the RCBO is 1P+N, you’ve asked how it switches the neutral.
• The device rating is at least the minimum for the heater’s wattage band above and no higher than the cable can carry.
• The cable is 4mm² (or larger for big heaters or long runs), with a fixed connection rather than a plug.
• The shower hose is non-metallic.
• The device carries the ST-SIRIM label; Type A is a worthwhile upgrade for electronic heaters.
• ST’s guideline says to press the test button on the main RCD at your board and on the heater’s built-in RCD, preferably once a month, and reset them. Testing the 10mA RCBO the same way does no harm. A protection device that no longer trips is the failure that shows up again and again in fatal cases.