I spotted this Mig Welder round at a mate's place on the weekend. It is a you-beaut inverter type with a maximum welding current of 220A. It comes with a 32A D-Curve MCB as a main switch. To cap it off, it comes with what appears to be a factory-fitted 15A cord and plug. Out of curiousity, we put the clamp meter onto the supply conductor and my friend did some practice welds. Wound up close to maximum, it laid down a nice thick run of weld with the clamp meter reading just over 30A. Since this was connected to a circuit breakered at 20A, I was expecting it to trip after a little of this treatment, and was not disappointed, it took just over 2 minutes of this treatment. Does anyone know the Australian/New Zealand regs well enough to tell me if this is legal? I am assuming that the maths goes something like 30A at 50% duty cycle equals a 15A cord, but I would like to know if the regs support this. Seems like an accident waiting to happen to me.
Hey Mark!, What brand of welder is this and where is it made?
I take it that this is a commercial welder being used in a domestic workshop?
Welders themselves are only designed to run at a given duty cycle to prevent the internals over-heating, even with fan-forced cooling.
Running a welder at "full noise" for two minutes straight is just asking for trouble.
If this welder had a 15A plug on it, how did you connect it to a supply when the earth pin on a 15A plug is larger than a 10A type?
I find it very strange that something with a cord on it has a 32A D-Curve MCB in it and would guess that it is only there to protect the internal componentry of the welder, not the supply cord.
Usually, welders have an information sticker on the inside of the cover (where the wire spool lives) that should tell you everything you need about supply requirements, wire sizes, current and wire speed settings. Then again, if it is an "out of town" welder, the supply data could be very misleading.
If this welder is going to be used a lot, I'd suggest that a dedicated circuit be installed for it, with a higher rated plug/socket arrangement, I've replaced I don't know how many 10 and 15A plugs on MIG welders, the pins just can't handle the current and usually start to melt the plastic plug body.
Of all the things I took note of, the brand was not one of them. I will find out tonight. It was a name-brand welder and not some home-made lash-up. Commercial welder in a domestic workshop, yes. Rated at 60% duty cycle at full output current. My friend welded up a box from pieces of 6mm plate. Not a completely continuous run, but 8 x ~150mm welds in quick succession. He is going to be adding extra steel beams into a large trailer of the sort usually pulled by a big-rig type truck, and he was quite adamant that the test weld was fairly typical of what would be needed on this job. The socket outlet in question was a 15A, in keeping with the 15A plug on the welder. The MCB is built in to the cabinet of the welder, and serves as a main switch. Presumably it also offers some protection to the welder if it suffers a fault internally.
I wonder if the distortion of the mains waveform by the switchmode inverter is causing my clamp meter to give a reading higher than the true value. The fact remains, though, that the welder does draw more current when welding than the rating of the plug and cord, and only gets a rest between welds. Safe? Probably, given good upstream protection. Legal? I have doubts.
Welder is a Kumai FR200A. Spec sheet is FR200A Spec Sheet I have checked with other electricians, and with my dad (a retired inspector), the commonly-held opinion is that the people who sell these welders are cowboys. Replacing 15A sockets and plugs that have been fried by a welder has been quite a common call for decades, and nuisance-tripping circuit-breakers are a well-known issue. Most people put up with it because it is too costly to install a 32A feed and socket outlet. The fun starts when someone re-wires a fuse with 2 x 15A wire to stop it blowing...
The fun starts when someone re-wires a fuse with 2 x 15A wire to stop it blowing...
Used to be done on building sites. The person doing the welding would bring along his own Federal fuse wedge, suitably uprated fuse wire, and temporarily replace the one in the fuse box with it for the duration of the welding. I must confess my own welder has a 10A plug on it for convenience; funnily enough the person doing the testing and tagging at the place from where it came didn't see the notice on the side to the effect that it must be fitted with a 15A plug. Melting plastic plugs are best replaced with bakelite ones, though haven't seen any new ones for a while; the HPM 99 is particularly good.
Mark, If I were going to buy a welder of that sort of capacity, the cost of the circuit to run the thing would probably be the last thing on my mind. I hope the guy has started saving up for his next power bill.
That welder should be at the very least (with an input rating as stated) 1Ø 400V probably even 3Ø.
But no, this is just rediculous, importing non-compliant gear like this gives everyone in the importing business a bad name that most simply just don't deserve.
Digging a little further into this, it is not just one brand of welder that is guilty of overloading supply cords and outlets, it would seem to be endemic. This, from the sales brochure for the SteadyMig 206, sold by one of NZ's biggest welding supply current : "Input Rating @ 230V Single Phase : 3.5KVA @ 95A 18.8V, 15A Primary Draw". Since this welder is good for "60% @ 125A, 20% @ 200A", it seems a safe bet that at 125A the primary draw is nearly 20A and at 200A just over 30A. This welder is supplied with a factory-fitted 15A plug and cord. Even the 206's little brother, the 165, will draw a calculated 22A at full output. I do not think that these are isolated cases, it looks like the formula that is being applied in the welding industry is that the primary draw x duty cycle must be no greater than the rating of the plug and socket. I am going to inquire about this with the Energy Safety Service. I will post their response when I get it.
BTW, Mark I hope your mate has NZS 4711 in the work he is looking to do. NZS 4711, pertains to the certification of welding work when done manually. This is normally called upon when structural welding in Stick, MIG and (to a lesser degree) TIG welding occurs.
I sat 4711 back in 1993, it cost a lot of money, you can only sit it in different welding types and "positions"
I sat the exams in Stick welding in Vertical up-hand, down-hand, Overhead and rotary drum, Low Hydrogen, Hard Facing, Horizontal down-hand.
I also sat in MIG with up-hand, down-hand and Fissure welding.
I still hold 4711, it has cost me a LOT of money over the years to hold that certification.