For folks who want to look for good advice, just ignore the last few posts.

Will be redoing the whole house wiring setup next year when we replace the roof with recommendations from here.

Its thai style electrics with probably 5 different local sparkys over the years having a hand in what weve got at the moment.

That main board with knife switch is the third different one since we started.

Might have to employ the no ticket no work theory but that will be hard to come by.,

Question,

If the wiring at the moment is not big enough,worst case scenario

It will just short and no power to appliance if fuse doesn't blow?

Question,

If the wiring at the moment is not big enough,worst case scenario

It will just short and no power to appliance if fuse doesn't blow?

Are you talking about the 600m span from the meter? That's maybe OK but depends on your internal demand.

If you get a breaker box (CU, DB, whatever), you could separate the shower heater from the pump and from the other electric draws - along with a 40amp RCBO main breaker (for example). Then, you should not be tripping any breaker from over-current. Your current 25a fuse is for EVERYTHING and when everything is turned on, that's over current for the fuse. Look at pinned topics for correct wire size.

Nothing should "short" under normal circumstances.

Again... if when you turn on the shower and lights dim not only in your house but the whole neighborhood, that would be PEA grid supply issue.

A rewire is absolutely in order, nobody is going to argue with that, it's really just how urgent it is.

As to existing wiring size, that rather thin looking link from the knife to the fuse is showing no signs of overheating. So long as our OP doesn't go with anything bigger than a 30A RCBO then he will be no worse off than he is already with the added bonus of shock protection and no need to buy fuses.

If, as he says, he is going to replace the existing 6kW heater with a 3.5 or 4 kW unit then the situation can only improve.

Just wanted to say thanks to all who helped contribute on this thread.

If it adds a bit more safety till i get the lot redone.

You can see what i'm up against with the shower install.

How's the water temperature from the new heater?

Lights not getting quite so dim now?

Be interesting to see what the voltage drops to when the heater is running now.

Still having the voltage drops and they vary at different times of the day.

Although the peak cold season has gone with reduced water flow the heat coming out is great.

And it sure does feel safer having that earth leakage breaker up front now.

Good/bad news is the main line maybe coming my way later or early next year.

Here come the neighbours living in straw huts with dogs and chickens.

If only i can convince them to spend the money instead on a safer better road,but the locals dont seem to mind knocking their new utes around on crappy roads.