I'm here visiting a country in Southeast Asia, and in the house I am staying the water heater socket is broken/corroded (working intermittently, with visible corrosion on the live connection). I started replacing the broken socket for the water heater (Panasonic DH-4HS1P), but then I noticed that the heater has been installed without any earth connection. From the wall there's just a live and neutral (brown and blue) going into a circuit breaker (2P, 20 A; just to protect the wire, not an RCD/GFCI) then into the water heater. The water heater earth wire (ground, PE?) is not connected to anything.
In the instruction manual for the heater (found here
https://www.panasonic.com/content/dam/Panasonic/ph/en/PDF/productPDF/2023/Operating-Instructions-DH-4HS1.pdf) it says "
The Unit must be earthed."
Is it safe to just fix the connection and wire it back as it was? What do people think? Apparently it's been used like this for years. What are the real and relevant safety issues?
Could the corrosion itself be a result of missing PE? Leakage currents mixed with the humidity causing electrolysis or arcing?
Any advice on how to proceed?