Hello All,

I had already run the cable when I picked up the heater.

The instructions say to use 4mm cable on a 20Amp breaker.

I had guessed using Crossy's guide that 2.5 would be ok.

No fault directed at Crossy. I think he has done a sterling job.

Anyway some advice from the experts would be nice.

Do I really need to rip it all out and put the 4mm in?

Cheerio

Blair

I wouldn't rip it out, 2.5mm should take over 5kw/20+ amps (nearer 7KW absolute max) However, you will be lucky if your mains supply will will deliver that anyway as the electric here is shit at the best of times.

I would ensure you are well grounded, you have regularly tested the breakers, and don't have anything conductive in the shower, you will then be about 300% more safe than the average Thai...besides, can you actually GET 4mm here? Copper I mean, not their aluminium or "plated" crap? I think that the safety side with breakers etc. would be a wiser move than to rip out your existing wiring.

Pretty much agree with Bill^^^, yes you can get real copper here.

3500W @ 220V = 16A, well within the capabilities of 2.5mm2 on a 20A breaker. Use what you've installed with no problem, your only issue could be on a long run (25m+) with volt drop reducing the power available, certainly no hazard though.

That said I would have run 4mm2 for a water heater anyway, in case the water wasn't hot enough. But hindsight is always 20:20

Yes I would have thought so.

Well that is good I will just finish the install and leave it at that.

Thanks again.

What is the distance between the heater and main breaker or power source?

With 2.5mm you can go up to 50M without more than a 5% voltage drop.

Your pushing it painless but I think you will be fine. 20 amp breaker - yes.