Good day fellow forumers!

I've hired a contractor to do renovation for my parents' 2 storeys old house.
I've asked them to totally knock down everything inside the master bedroom toilet.
And I've asked them to change new wiring for the (instant) water heater shower unit too.

So, just now I went to check the progress and I found that the contractor used 2.5mm for the live wire,
but only 1.5mm for the neutral and ground wires. And they tiled it up already. Is it dangerous?
Should I ask them to knock down the new tiles and redo the neutral/ground wires with 2.5mm ones?

My parents' house is on 3 phase power. And there is a sub DB upstairs powering 3 bedrooms.
The said downsized wires are upstairs in the master bedroom toilet.

Thank you experienced sifus for your inputs!!

Thanks so much for the quick reply!!

Around RM20k+ for master bedroom toilet and garden renovation. For the water heater single point wiring is RM260.

The house is on 3 phase, this one doesn't matter right?

Yes, the wires they used is Sirim MS 2112-3 certified, not sure what brand though, I can't find the packaging. 2.5mm wire should be good enough for 3kW water heater right?

Yes, after learning from the sifus here, I've installed an EPS 10ma RCCB a few years back.


OK, I will ask them to re-pull the wiring tomorrow or worst case knock down the new wall tiles. Thanks for the advice again!

This post has been edited by ivan89: Jan 20 2024, 02:25 AM

Understood, thanks lj0000, ceo684 and Selene Yeo for the advice!! Sorry for late reply, was busy juggling work and renovation.
The contractor basically just pushed the blame on his staff. Excuse is 2.5mm finished, so his staff used 1.5mm. Quite BS la.
I warned him to be more careful and professional.


By the way, I've also decided to change completely new wiring for the common bathroom's water heater from DB too.

I bought Mega 4mm wire for the contractor to use this time.
The (instant) water heater I bought is Deka 4.5kW high power version.
For the RCBO, I bought Schneider Easy9 25A, 1P+N, 6kA, C Curve 10mA.
Schneider RCBO somehow doesn't have 20A version.

1) Should I buy EPS 20A 2P 10mA 6kA RCBO Type AC instead?
2) Why EPS RCBO has 2 poles, while Schneider RCBO only has 1 pole?
3) Is RCBO only good enough? Or should I use MCB + RCCB setup?

Thank you all again!!