Ideally your *fixed* Tariff 33 wiring from the MDB to the hot water will be rated 32A, 6mm sq conductors. or 20A 4mm sq.
Depending on when & where the house was built - it is more than likely not the case if the house is really old.
2.5mm sq is the minimum conductor size for 15A as others mentioned. But why bother with that for a welder?
If you can only run single phase, then put in a dedicated 20A or 32A point. It's not expensive - you just need the correct conductor size - and you may already be lucky with your hot water service.... it may be a 4mm sq - enough for a 20A or 6mm sq enough for a 32A feed. You should have your sparky check it for you if you are unsure.
If the cable is already correctly rated, then you simply install an appropriate breaker in the MDB and the correct rated outlet on the end of the cable. - but first....
Couple of other things:
1. If the MDB switch is actually 25A, there should be a breaker or a fuse rated for the Hot water matching it. The wiring should also already be 4mm sq. Check it.
Commonly it was a ceramic 20A fuse, later a 20A breaker. Not many 25A fuses or 32A breakers these days but if there is, then luck is on your side, assuming the cabling standards were/are adhered to. It's more common to see 20A breakers in MDB's - mostly for stove / fridge / power. Anything more will have a dedicated single run - in accordance with AS/NZS 3008.1.1:2009
If the existing cable is appropriately rated , a single IP66 rated outlet should be installed if outdoors. Also, it is important to not install any other outlets on the circuit.
By law, the circuit is supposed to be on earth leakage. This causes problems with a lot of welders**. It is not uncommon for arc welders to trip an ELB when starting the arc, and some older MIG equipment can do the same. So.... to ELB ot not to ELB, that is the question...
I'm not an advocate of running a circuit without ELB these days, but if the home owner were to *cough* DIY, and the welding point was sufficiently marked as not being on earth leakage - or better still, used an IP rated enclosure with round pins instead fo standard flat ones - it all helps - then so long as they are aware that there is no extra protection from ELB - again so long as no other points are wired into that circuit (very important)
suggest that if you decide to use a blade type plug - use clipsal 56P320F,
but preferably a round pin style:
20A 250V
56P320(round pins) 56P320F(flat pins) 56PA320(round angled) 56CSC320
Round 32A industrial. Orange - best choice to stop other people from attempting to use an unprotected outlet.
32A 250V
plugs:
56P332 56PA332 56CSC332
Outlets:
56C320(20A round) 56320F(20A flat to match the 56P320F plug) 56C332 (32A round)
use the clipsal catalogue as your reference, order from L&H or whoever your preferred supplier is (schneider):The hot water is likely to still be on an RF mag switch - hence separate meter & hard wired connection for hot water (QLD - tariff 33), which will need to be disconnected from the meter and RF switch and back into the main bus by a licensed electrical contractor.Code:http://updates.clipsal.com/clipsalonline/Files/Brochures/I0000116.pdf
http://www.olex.com.au/eservice/Australia-en_AU/fileLibrary/Download_540224625/Australasia/files/Industrial
Bottom line...
If you can work with live mains voltages (DANGER) in the back of the MDB, then you need to disconnect the RF & mag meter, move the circuit & breaker to the main distribution bus for the Tariff 11 meter.
Every state has different requirement specifics, so the smartest thing to do is get your sparky mate to come around, and hook up the circuit onto the main meter for you. Don't kill yourself trying to do it, let your Sparky do it for you :angel:
If you run a nice big fat 3 core 6mm sq feed from the desired location of the outlet, to the back of the meter box, your sparky will be happy and hook it up and test it for you. It will ensure you get enough juice to power a giant tesla coil, or at least more than enough for a welder. If you go to the trouble of doing that, fit a round pin socket rated to 32A, and then it prevents others from using it as a household outlet.
It's not a difficult job, but there are some dangers involved. Also, in some states it is illegal to work on a meter box without removing the pole fuse first.
Check with your sparky first, before you decide to do anything, for your own safety. You never know how good the existing wiring is until it's checked.....
I'm not affiliated in any way with any of the manufacturers mentioned above. I simply have used their products in a number of installations before and found them to be robust and reliable.
Electrical Safety should be your main concern.
