if you can do some basic "proper" wiring, certificate is not a must .. just basic amps properly needed for for certain household stuffs ..

I installed Joven EC802 (quite old model) given by my cousin, but the heat sensor was broken .. I just bought the sensor from Joven factory (Kota Kemuning) installed myself and rewire the back panel (previously I was using Panasonic heater whereby the rear case inlet differs) ..

P/S - I can now do 3 phase wiring, done few projects (I dont have any certifications)

call some Malay guys, u can find in FB's offering wiring jobs ADs .. they're actually good ..

grounding is a must, if not the heater will go offline after certain time of usage .. for shower heaters;

Live and Neutral to use 2.5mm with single max 20A (RCCB), Earthing can use 1.5mm, no problem ..

in my personal case which is Joven model EC802 (outputs 3.3kW), uses 15A so I share the 20A RCCB with kitchen LED lights which is total of 3 fluorescents

if other higher kW shower heaters may consider 25A RCCB ..

sure this is Joven? .. more like like Livinox or Panasonic

.. and wait, ure mom relative is not ure relative?

I see .. nice brand but obsolete in terms of parts, and is the current unit broken? why he asked to change to Joven?