300mA better dun put la. Confirm six times killed, then only trip

The higher the better for them only because 1. Lowest price (lousy sensitivity is dirt cheap on 3phase) and 2. very hard to trip (no callbacks from owner). Which is ok for industrial use but at home, what good is human dying 6 times over ☠☠☠☠☠☠ before it decided oh ok..lets trip.🥱

All the expensive specification i.e. 63A max load, 30mA top tier sensitivity, 3phase supply and good brand like ABB/Hager using VI design (works regardless got voltage or not) will cost 290-300 bucks for RCD alone easily exclude installation.

At 300mA 🤦‍♀️, VD type (won't work if no voltage), non high end brand (Schneider and below) easily half the price but ZERO life protection. ☠☠☠☠☠☠ It only protect building for FIRE 🔥 protection. Not to mention, its illegal to use 300mA in residential...CHEAP mah! 😅

3phase and 10k reno should use ABB or Hager for the mains RCD 30mA (0.03A)
EPS boleh pakai lah..local brand.. but I personally prefer ABB. Safety item really you get what u pay for

⚠️ Also ensure you have individual 10mA (0.01A) per each water heater unit.

If MCB is EPS, can still mixed with Hager RCD? Yes

So I just tell the electrician to change the 300mA to Hager/ABB RCD 30mA? Yes 

If I got 4 toilets with water heater, then have to use 4 individual 10mA RCD? Yes 4WH = 4x 10mA RCD's is best. If DB no space issue, can use Schneider 25A 10mA RCBO

Can, I'm using single (whole house) 30mA RCD w 3ph supply to type this

no need lah, this is 2022
we are not in the business of selling RCDs
MS1979:2007 COP55 mentioned can put one single whole house RCD [at origin of installation]
[attachmentid=11127769]

the code in force is Electricity Regulations 1994
back then:
a. nobody use LED light. all use leaky fluorescent tube.
b. nobody use inverter at home for AC and fridge.
c. my Sony VCR also leak current, always kena zap from metal body. it came with 2 pin plug.
d. people use CRT TV

nowadays
appliances are made better with much lesser leakage current
meaning to say there's no actual need to use so many mains RCD's [this is in relation to some who propose one 30mA and one 100mA]
when one single whole house RCD 30mA can comply fully.
note its "maximum tolerance allowed" not "identical die-die must be exact"
[attachmentid=11127768]

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as for your suggestion it is not wrong.. actually split load design is to have half the lights and half the sockets on each mains RCD (two mains RCDs), not split by lights vs sockets. Because again, 2022 everyone using much better made items with much lesser residual leakage current.

to expand on your suggestion, 3 phase supply CAN also be protected with 3x single phase RCDs.

split load pro: so in the case one RCD trips, you still have half the things running until user figure out what's wrong
split load con: cost of extra RCD