Ahh no wonder.



Urmm lets say now my current usage now is 50A and then there is a leakage of 0.1A somewhere, will this 40A 0.03A RCCB trip?

For RCD it will trip.
Main RCD max current rating (40A part of that 40A 0.03) should match or exceed the main MCB rating (40A).

Please help me to check if my house wiring is correct.

My 3600W water heater shares a 16A MCB with the lights/fan in the kitchen, bathroom and 3rd bedroom. From what I understand light points use 1.5mm wires, so are the wires being overloaded now?
So far no problem. The heater was fixed 5 years ago by the shop people.

Another thing, all my light points use 16A MCB, while sockets use 20A. Should I change the 16A MCBs to something lower or it doesn't matter?

Lights should be C6 (6A) for safety. I don't think the installer would ever use 2.5mm for light circuits.

MCB must be rated lower than the cable safe load.
I suspect the WH is running on 1.5mm if its tapping into the light circuit if the WH circuit was not originally built in (wrong).

Shop ppl wont care.."not my house syndrome"

This post has been edited by ceo684: Oct 17 2021, 10:23 PM

This confirms my doubts. I wanted to DIY replace the heater but saw all these mistakes.

One more thing. I have another water heater, this one has its own circuit and is using a 16A MCB. Everytime the heater is used there's a buzz coming from the MCB. This has been going on for over 7 years. 2 years ago I changed the water heater to a new one and the buzz still happens. The installer said it's normal. Is this really normal? I suppose I can get the MCB replaced as the next troubleshooting step but keen to hear your experience on this.

Weird sounds are indicative of overload (close to redline) or loose connection.

What MCB brand are you using? It'll be good to check your cable sizing whether 1.5mm or 2.5mm...the former looks very thin. You can off the whole DB to check safely. The cable going out from MCB controlling WH should look like the sockets one..NOT like light circuits.

MCB brand is UMS.
Wires are 2.5mm and the screws are tight.

I think I'll get a wireman to pull new cables to both the heaters. Maybe install RCBO also.

Tumpang tanya
House rccb trip few times lately thunder
Notice the plastic part cracked
How much normally is the charge to replace it ah?

Depending on you're 1ph or 3ph supply, and how many amps. Take a pix and post lah.

Residential not all single phase ka?

I use 3 phase at home. The pricing of the device also depend on rated current. Hence if you're talking about single phase RCD, e.g. from ABB.os its 77 for 40A 30mA and 127 for 63A 30mA materials only

This post has been edited by ceo684: Nov 6 2021, 12:13 AM

Maybe ur house bungalow lo
Mine just normal terrace house
Add labour around 100?

Wah landed!
I stay in highrise.
Long time ago supply only 40A per phase due to wire size small. So not very useful, hence prev owner put in 3ph so can use up to 120A.

U supply the parts yourself will be cheaper than asking the electrician to buy for you..But to get the right part w/o pic of ur existing is hard..err on the side of 63A 30mA 2P RCD. then get an electrician or wireman to wire it up should cost around there. For plug and play replacement you can shop around FB..some are pretty cheap on labour. My usual sub con costs from 200 to show up.

Ok thanks
Got it done 180 with ABB
Fair deal i guess

Hi All,
does anyone know if water pump require a RCBO protection as it also dealing with water ? my current water pump has a dedicated MCB without RCCB, it relies on main RCCB with sensitivity of 100ma.

Here in MY whilst the appliance is not in a wet floor area, it won't be covered by ST reg w.r.t water heater. But if its outdoors then should have at max 30mA RCD.

b) Regulation 36(2) of the Electricity Regulations 1994 states that for
a place where the floor is likely to be wet or where the wall or
enclosure is of low electrical resistance, protection against earth
leakage current must be provided by a residual current device of
sensitivity not exceeding 10 milliamperes;
c) Regulation 36(3) of the Electricity Regulations 1994 states that for
an installation where hand-held equipment, apparatus or
appliance is likely to be used, protection against earth leakage
current must be provided by a residual current device of
sensitivity not exceeding 30 milliamperes;


Over in UK - https://www.electricalsafetyfirst.org.uk//g.../garden-safety/ it is recommended to fit an RCD for water pump.

In your case..I would suggest to change the 100mA main RCD with a 30mA RCD in the event rainwater drip in onto the pump during thunderstorm. Then it would cover all bases including your 13A sockets.

Modern RCD from ABB, Hager come with anti nuisance trip feature, it will not nuisance trip much compared to those sold before 2000, about 97% reduction.

thanks for responding, my water pressure pump is located on ceiling and covered by roof, hence it is at dry area.

do you still see a need for a RCD for extra protection ?

many have talked and discussed that RCD is mandatory for WH, little is talking about water pump here in malaysia.

on your recommendation on changing the main RCD from 100ma to 30ma, would it be too sensitive with unnecessary trips ?

i see many electrician uses 300ma in main RCD.

What is the likelihood the roof leaks from thunderstorm/strong wind esp in older homes, and causes the pump to be flooded?

RCD has dual function to protect life, and protect against fire.
Assuming only a single unit (main RCD) is installed, 100mA you already breaking Electricity Regulations 1994 as all the 13A sockets can kill humans at 50mA.

Itu electrician qualified or not? You are not running a dodol machine at home that will trip a 30mA on normal startup.

Nobody in their right mind put 300mA in residential. In SG and UK, everybody put 30mA for residential. Maybe Malaysia got stronger human than them can sustain 230V currents lah..

I personally use all 30mA.

As mentioned, modern RCD has anti nuisance trip so it does not trip on false alarm like those made before 2000.

This post has been edited by ceo684: Jan 13 2022, 02:24 PM

chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/viewer.html?pdfurl=https%3A%2F%2Fwww.waterpump.co.uk%2Fmedia%2Fwysiwyg%2Fmanual%2F5711497234216.pdf&clen=6523985&chunk=true

saw this from grunfos scala2 spec doc, they do recommend to install RCCB with less than 30ma.

Recently upgraded to 3 phase for my house reno.
The contractor say this device the higher the better.
True?

Edit: found out mine is 300mA

This post has been edited by BL98: Mar 29 2022, 03:34 PM