Shower Water Heater

[Oscar2]

Thank you gentlemen.

[electau]

Strange there is no grounding point in the heater - never seen that before.

I notice that the incoming black wire is connected to the N - I know TIT and anything can happen but I always assumed the black to be the L wire.

And whats that smaller gray wire coming from the N to the small circuit board with the led?

The green wire needs an earth ground coming in on the opposite side of the white terminal block. The metal harness strap on the empty side of the t-block is the indication that a branch circuit will enter there.

The MCB that electau talks about is probably a MCCB (molded case circuit breaker). They are slow and even unreliable at times. They protect the wire from overload and ground fault and are resettable. That's about it. Fuses are much safer, trip quicker, only the leg with a fault trips, and fuses protect against arc flash. Use fuses for selective coordination instead of breakers.

The internal wiring -sensing/control- isn't my deal.

MCB minature circuit breaker with fixed overcurrent non adjustable setting, may be DIN rail type must trip in less than 0.4secs on an earth fault with a compliant earthing system.

[electau]

The test button provides an out of balance between the L and N so the RCBO will trip. It is not a short circuit. The 15mA is the range setting for earth leakage, ie residual current in mA.

The 32A is the normal current rating for the device ( RCBO) and will trip on a short circuit ( L to N ) and trip on a sustained overload.

Heater must be earthed with a compliant earthing system.

The earth fault resistance for a 30mA RCD is 230/0,030A=7666 ohms. This figure is impracticable compared to the resistance for voltage drop, but it shows that RCDs are acceptable when the fault loop resistance is high. If an MCB/RCD (RCBO) is fitted then the automatic disconnection requirement will be satisfied.

Automatic disconnection must occur if the touch voltage exceeds 50VAC in normal conditions and 25VAC for damp areas. Touch voltage only occurs under earth fault conditions.

[mistabent]

I'm late to this party, but I can confirm that the Hi-Tek unit first referenced in Post # 22 is a legitimate RCBO and the price was the correct price. It varies slightly by store, but most places I've seen in Ubon have the 30A 15mA model at 212B. After talking to an experienced Thai sparky friend, I ended up buying a very similar 32A RCBO made by Haco for 370B. I was told that this brand was sturdier and longer lasting and I agree that in the store it appeared to be tougher, made from higher quality plastics, and with a sturdier switch, but only time will tell with both brands. I've also seen the same thing made by Safe-T-Cut 32A 15 mA priced at 390B (a small RCBO just like the one pictured above, not to be confused with their much larger and more expensive whole house models).