Hi all

Would like to ask, does anyone install individual RCCB outside the bathroom on each of their water heater?

There is a central RCCB at the DB box in the living room, but I've read somewhere for water heater it's best to install RCCB nearest to it possible. Was thinking of installing individual RCCB and ELCB as well, but have read that if you have RCCB you don't need ELCB, and some recommend MCB + RCCB.

Already install MCB for each of the AC outlets and the oven.

Your advice is highly appreciated.

Maybe talk to these guys as shown here.

Your intention is correct...layering electrocution protection
MCB 100ma electrical fire protection
Water heater circuit 30mA RCBO residual current breaker and overload protection (layman calls it rccb but technically it's rc+o breaker)
Heater appliance ELCB built in. Newer ones also have 10ma RCD.

Some may add 10mA at the heater master switch also for added protection due for hook on contact when electrocution caused spasms that the user is unable to let go of the energized device.

The reasonable protection principle is redundancy....in case even the protection circuitry fails over time, there is another along the circuit to back it up. Just don't overdo.

The other is to engage a qualified electrician to check the integrity of the circuit at water heater after installation. Or a renovation that touched the bathroom and may have perhaps involved the water heater. A checker auditing an installers work. Usually the head electrician will do that. You never know...and don't want to find out the shocking way.

Also look up isolator barriers which are now mandated for storage water heater installations. The company that produces them is called showertec. And also non metal type shower hoses.

This post has been edited by halcyon27: Apr 8 2020, 10:51 PM

From ST guidelines ..

The recommended 4mm2 wire for 20A mcb to Aircon & water heater..

I suppose if you install new might as well use the recommended sizes.

i used 2.5mm2 for water heater and aircon when i renovated yrs ago so better confirm with your wireman if you want the 4mm2..

Agree ..

The RCBO combines both mcb and rcd in one device..

For water heaters better use a 10mA RCD or 10mA RCBO per ST guide.

RCCB (residual current circuit breaker) & RCD (residual current device) is the same thing and operates via trip relay current difference in mA betw live/neutral. No need earth wire to operate. Installed in DB..

ELCB (earth leakage circuit breaker) operates via voltage difference and needs an earth connection to operate..which is factory installed in instant water heaters cause cannot let the leakage current electrocution risk. So a low Impedance earth connection is important.

old houses sometimes have them (big black fuse switch with a yellow button) but regulations now is RCD's ..

WHOLE HOUSE
Recommend 30mA as little use to put an insensitive RCD unless you run huge motors (industrial) use.
According to Hager, shock exceeding 50mA is lethal.

Refer page 2 -  Technical_Handbook_10x15cm_English.pdf ( 3.41mb ) Number of downloads: 324


WH 10mA RCD
RCD 10ma need to be combined with the MCB 16A or 20A depending on your load amps of water heater.
There is no requirement to position the RCD outside WH. In DB box also same protection as the RCD work on differential L-N. If 13.000A incoming on L, at least 12.990A must return otherwise it will trip (current loss = fault somewhere).

You can choose either to add on RCD 10ma + combine with MCB,
or
RCBO (all in one) device - RCD+MCB in one slot (eg Schneider)

They cost about the same..
EU made ABB or Hager RCD 17x-19x bucks
CN made SE RCD is about 105
CN made SE RCBO 175

Recommend match back the brand you have in your DB box unless its some local made/CN stuff that doesn't get international certification.

Do note 2P RCD 10ma usually take up 2 more slot in DB box. Whereas for the RCBO you can just replace MCB with it directly.

Also need to identify which is the neutral wire dedicated for WH circuit.
In my new place built 2018 no problem they actually put in some china brand RCD but it is combined 40A 10ma for two WH circuits (which even ABB, Hager unable to produce such model). I replace with ABB 10ma RCD and split to two circuits/two RCD 10ma (i.e. dedicated RCD to one circuit) as they should be.

For my old place built 1995 i add in RCD 10ma keep on tripping when on WH. WH no issue with 30ma main RCD. Suspect wiring problem with original 1995 wiring so I run dedicated line to WH from the RCD 10ma in DB box then it was OK, since its MCO I only have 2.5mm cable but it works fine for temporary solution.

Aircon load 4-7A only for 1-1.5hp typical operating load.
WH is the one that heat up wires as typical load is 13.7-16A depending on power rating.

This post has been edited by ceo684: Apr 9 2020, 04:24 PM

i have RCBO just before my storage heater. But honestly, how many times you would test it in 1 year if you were to put it just before heater?

Maybe once a year should suffice if it's a good brand and not some kind of questionable CN brand..

schneider brand..
but as i recall, those in DB, need to test like once a month

What does WH means

water heater

Planning to replace replace old DB in house, currently only ELCB no RCCB.

Good idea, but it's troublesome to change to bigger DB Box and find the neutral wire dedicated for the water heater and need also separate the neutral bar for just water heater.
For simplicity i just change the socket or plug with built-in RCBO according to usage amphere. All of my water heaters and air conditioners are with RCBO either with socket or plug. Much easier

I have this 10mA but only 13A for water heater.



This post has been edited by amco: Aug 29 2020, 03:28 AM

That may work for aircon but WH at 3300W / 230V = 14.3A, 3600W = 15.6A which is a fire hazard to knowingly overload the 13A socket.

Schneider 1-DIN module RCBO is available so it is just direct replacement of the WH MCB in DB box.

This post has been edited by ceo684: Aug 29 2020, 03:48 AM

Actually, I am using China's plug & socket which is 16A for water heater with tank. That 13A is suitable for AC and tankless water heater.

What brand is that? Where to buy

Shud use sirim approved sso etc or later difficult to claim insurance if incident happen

I don't think it's suitable for water heater since normal running already exceeded 13A.


The correct one should use 30mA for whole house RCD, and 10mA RCD specific for each WH circuit as per ST guidelines.

can anyone recommend an installer for external rccb ?

This post has been edited by babybaby1988: Apr 19 2021, 11:28 PM

Well, it is supposed to be inside the DB box.
Any qualified electrician will be able to handle the installation of 10mA RCD.

Generally if theres enough space in the DB box for 2 modules ("fat RCD") then no problem to add it in, else may need to consider using slim 1 module RCBO instead. U can take a pic of the DB box and show us for better commentary. No need to open until can see wires. Just the user accesible portion will do.

There may be false tripping if your WH circuit is not dedicated circuit but running on looped (shared) neutral as the 10mA RCD is a highly sensitive device.

This post has been edited by ceo684: Apr 19 2021, 11:03 PM

attached is my current box, its messy as i requested my electrician to change all fuse mcb to trip mcb, but somehow my autogate and bell stop working and he cant seems to figure out how.

So i asked him to stop work and tmr another electrician will come.

So i told this new electrician i want RCCB outside toilet and i am not sure he understand what i want so he said he will come and see first


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Oh dear. Best to get the new electrician to do complete overhaul change all the MCBs to one brand (ABB/Hager). The MCBs around RM7-8 bucks each only at the electrical store.

As you can see, between the taller ones and the shorter ones there are physical differences. This is a very dangerous situation as it is a loose connection (can catch fire) for the top row of short Hager fuse boxes.

Judging from the age of the whole setup, it is likely that the wires has broke internally for the one that powers your autogate (internal injury of the cable).

Normally we will advise user to turn off the questionable circuit until the electrician comes - but in this case there are alot of LIVE WIRES hanging around with masking tape as insulation - so please do NOT touch it at all

This post has been edited by ceo684: Apr 19 2021, 11:49 PM


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