The element on our hot water cylinder died late yesterday. While I was draining the cylinder I went out this morning and bought a new 3kw element based on the size of the cylinder. It measures up at about 135 litres. Now that I have the old element out I see that it is a 1.5 kw element.
Will the wiring be ample for a 3kw element? The house is a mid 1970's house. I see from a copy of NZECP 51:2004 that water heater wiring for up to 3kw heaters is supposed to be 1.5 mm sqr. My guess is I should be OK. The wiring is three strands of about 0.9mm diameter which I've roughly calculated to be 2 mm sqr.
One thing that has made me doubtful about the circuit capacity is the fuse label. The fuse has 5 amps embossed on the ceramic case, however it's anyone's guess what size wire is fitted. 5 amps isn't really sufficient for 1.5 kw so I'm suspicious someone in the past has used a 5 amp holder and put in heavier fuse wire.
A 3kw element will need a 15 amp fuse.
I'm prepared to go back and swap the element but the only smaller size element I can get today is 2kW which isn't a big stretch on 1.5 kw. However if the 3kw will be OK I'll stick with that.
I'd appreciate thoughts, feedback from those with expertise on this.
Like most other things about this place I suspect the previous owner just cheaped out when element was replaced last time and fitted a small element.