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

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

water heater

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

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.

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

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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Yup, as this 10mA is for WH circuit only.

Whole house one still return to neutral common link so no issue for the whole house RCD.

Prev owner contractors did funny things for connecting the WH. I pulled new dedicated cables for the WH and all good

Your new electrician should be able to handle?
Since new wiring (new set of LNE cables) being pulled it may make sense to procure the material yourself and ask him to come to install as labour only if agreeable and also it will save some cost lah.

Ideally, following ST guidelines, core scope of work will be
Pull a new set of 2.5mm² LNE cables for each AC unit
Pull a new set of 4.0mm² LNE for each WH unit
Add in C20 MCB for all the above circuits
Add in 10mA RCD to the DB box, one RCD for each WH circuit
Add in 20A double pole WH switch for each WH circuit outside bathroom
Add in 20A double pole switch for each aircon

Additional nice to haves:
Whether to conceal (need extensive hacking) or just run surface mounted PVC conduit (no need extensive hacking, minor hacking required) will be a price+aesthetic consideration.

Replace whole hse main incomer from switch fuse and old 100mA RCD - to new whole hse RCD 30mA + new whole house MCB (40/63A depending on existing cable size)

This post has been edited by ceo684: Apr 20 2021, 06:36 PM

roughly circa 2100 for the electricals; and the rest will be the hacking work.
Sounds about right.

You need to plan out how to reposition it. When there is limitation of wire length, this becomes tricky.
I've done replacement of DB for such hangmen tight wires that it may require some creative placement (to ensure everything can be connected).
For the wiring that came with the house.. that one no comment la can't do much; but for new wiring enough slack inside the DB box is important so you can configure accordingly.

Not sure how the NEW DB (current condition) look like but from the OLD BOX you can isolate the whole house off by disabling the fuse marked with Danger High Voltage (pull out the fuse and put it safely away on a table).
The incomer will be a problem to shut off but if you can shut off the whole house using the fuse (pull out) then you can work on the downstream components AFTER it.

Your new RCCB (30mA) can replace the existing one (i.e. second module) of the OLD BOX pic AFTER you have isolated the power.

Ref OLDBOX2 pic:
Busbar and 16mm² mega kabel pigtailsin the correct RED/BLACK colours can be purchased as loose cut (by meter).. LINK (Loose cut 16mm)

This post has been edited by ceo684: Jun 9 2021, 08:43 PM


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Whoever did this should be banned from working with electricity.
The original (OLD FUSE) is 40A (sized for 10mmsq cable). Cannot suka suka replace with 63A breaker without changing ALL the wire to 16mmsq.
Should be fitted with C40 (NOT C63). 🔥🔥🔥🔥🔥 risk - cable all burn but the master MCB will not trip.."haven't overload >63A mah!"



You can park the new RCD at the far right and just extend with new pigtails.


I see the new one also 100mA Should return it and request to change it to a 30mA RCD instead as 100mA whole house is NOT up to code.
A single phase 40A 30mA RCD is not expensive. It make a world of difference between a 30mA or 100mA if there is a fault situation passing thru a human.


For further reading can see BEAMA (UK/BS standards) on RCDs.  BEAMA_RCD_Handbook__Dec_2010_.pdf ( 4.78mb ) Number of downloads: 51


Only in Msia lives are cheap- we still sell 100mA and 300mA openly






Unmodified file rotated for easier viewing


This post has been edited by ceo684: Jun 10 2021, 12:14 AM

Personally 30mA whole house will be fine since total amps IN = total amps OUT regardless how it is looped after that.

I run 30mA whole house myself no issue.
My parent's place also had this same problem where the WH circuit was shared with other things and its NOT dedicated. 10mA always trip. Resolved by running dedicated LNE circuit to the WH.
The difference is that the SINGLE circuit 10mA RCD had "unexplainable and unaccounted for amps from other devices" that the 10mA cannot account for = trip first talk later, save life more important.
Whereas for WHOLE HOUSE 30mA.. as long as total amps IN = total amps OUT (since there's only one IN and one OUT cable back to TNB meter) it will be fine, even high sensitivity 30mA also OK.

Anyway, congrats for putting in the 10mA RCDs for better electrical safety.

The difference is in 10mA WH circuit:
Even in cases where the WH circuit is actually shared neutral and trips the 10mA (because the neutral also contain other appliances' return so its imbalance with the incoming amp), this will not affect the whole house RCD.


This one can be solved by (a) correct way i.e. running a dedicated LNE circuit to that WH itself, as per code, without looping or
(b) use dirty trick (not so code compliant but likely to work without extensive hacking all over) is to install RCD as a spur i.e. AFTER the 20A switch (load side) and BEFORE the WH, so only that particular line going to the WH is balanced amps between incoming and outgoing.

Regarding the 63A MCB used on 10mm wire..
Changing the 10mm to 16mm will be expensive. In this situation, since your 63A will never trip before the 10mm cable is overloaded, the TNB cutout fuse will be your Plan Z overcurrent protection (between TNB meter to DB box) since that should still be on original 40A fuse.
The difference with MCB vs fuse, one can be reset in case of overload (just flip the MCB back on) whereas a fuse once blow already it need someone to buy a replacement, and that replacement fuse will not be available fast if the electrical supply store is closed.

Regarding 2.5mm cable used for WH circuits;
Should be OK-lah with 2.5mm for WH if its just 15-16A load, within spec of the cable, as long as its all 3kW class heater (3xxx W). You cannot install those highlands model with 4800W using 2.5mm cable.
2.5mm can withstand 21A safely.

That uncle cannot explain why these happened leh.. nobody is laughing



This post has been edited by ceo684: Jun 11 2021, 01:33 AM

Normally, a fuse is sacrificial i.e. rated lower than the cable to protect the cable from burning up.
The other way, cable will burn up first to protect a higher rated fuse from blowing.

The TNB to main DB (incomer) is 10mm also?

Having four water heaters on at the same time is 16Ax4, without adding on anything else. Upsizing fuse need the cable to be upsized accordingly as well.

The main switch need to be C40 MCB for it to trip on OVERCURRENT FAULT exceeding 40A.
Note: Just plain switch (isolator) without OVERCURRENT protection (ie No MCB function) does nothing to protect for OVERCURRENT.

When will MCB Slow Trip
In this case 51A > 40A its a sustained overload (MINOR OVERCURRENT FAULT) and it should "slow trip" using thermal trip within few mins.



I'm assuming you got a hager C40 P/N MU240A installed.
According to datasheet, https://www.hager-me.com/products/energy-di...u240a/30368.htm
min/maxi threshold value of the AC thermal operation 1,13/1,45 In (meaning between 1.13x40A and 1.45x40A)
for the 51A (divided by 40A rating) is around 1.27 In
this means a time to trip about 500 seconds based on Hager MU datasheet

‐-----
When will MCB Fast/instant Trip
(It will do a "fast trip" on the magnetic trip only if there is a SHORT CIRCUIT/MAJOR OVERCURRENT FAULT).

-----
RCD working principle is DIFF from MCB

For the 0.03A RCD yes this will be instant trip for CURRENT IMBALANCE (LEAKAGE PROTECTION).
The 40A on this unit is an indicator on how much total current can be safely monitored..but this RCD does NOT & will NOT trip in case of OVERCURRENT (which is MCB job).

RCD only measure "I-in = I-out + (tolerance of loss x up to 0.03A)". If the loss x higher than 0.03 (eg 0.032A) it will trip because "something is missing somewhere".

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

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).

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

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.

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

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