I have had a newly bought cheapo Toncon inverter DC tig welder sitting around unused for around a year and have decided to get it up and running. All power outlets in my shed run through an old fashioned isolating transformer via a portable distribution box for the leads. The user manual appears to recommend earthing the body of the welder separate from whatever the power cord provides, and has an external stud on the body for this purpose. The plug on the machine's lead has the earth prong marked as such.
My question is: should I bypass the transformer, and do I need the external earthing? If so, what is the best way to achieve that?
I am not referring to the earth for the welding clamp.
johotech,
Oct 8, 3:59pm
1. Your transformer is unlikely to be big enough to run the welder. 2. Get your shed wired properly by an electrician. 3. Get the electrician to test the earthing on the welder.
Thanks for your reply. The shed has been wired properly by an electrician. I had the transformer for years, so ran my leads through it. The welder was bought here on Trademe, but no actual documentation came with it. I will check the continuity between the earth stub and the earth pin on the 16amp plug.
gpg58,
Oct 8, 5:01pm
as jono said, transformer is unlikely to handle a welder, unless it is huge. even 1kw ones were big and heavy, a 3kw would be massive, any smaller you will blow its fuse (or burn it out real quick if none in it). I would upgrade shed to earth leakage, or at a minimum install a separate welder circuit via a earth leakage breaker.
budgel,
Oct 8, 5:16pm
I only had the transformer because as a chippie I stopped using it on site years ago and thought it would be useful as a backup in my shed. I went to using RCDs on site. Should I use one of those for the welder?
I posted the same questions on the motoring forum and a welder guy said the external stub is mainly for removing HF interference.
johotech,
Oct 8, 5:18pm
How long ago was the shed "properly wired"? If it was any time in the last 10 years or so, it should already have RCDs.
gpg58,
Oct 8, 5:20pm
Probably Still a good backup for small stuff, but RCD is best option definitely, as not limited to small stuff. (have not seen a tranny anywhere in many years now though).
budgel,
Oct 8, 5:50pm
No, I've lived here for over 20years. I will get the shed upgraded. Re the earth on the welder: The external stub has continuity to the body of the welder. The earth pin on the plug does not. Strange I thought, so took the outside cover off and the earth on the plug is connected to the large aluminium heat sink inside the welder, and not the body/case of the machine. I am wondering if this is legal. It is brand new and I have never plugged it in.
johotech,
Oct 8, 6:09pm
It depends. Does it have the double insulated symbol on the label?
But, on the other hand, why would they suggest connecting that extra point to earth, but not do it through the power lead.
As I said, a welder should have a Supplier Declaration of Conformity document which states that it was tested for sale in NZ.
budgel,
Oct 8, 7:34pm
No it doesnt have the symbol, I looked for the double insulated symbol as soon as I tested that connection, but I have never seen a double insulated symbol on anything with a steel case.
it has been suggested to me that a seperate earth is desirable to limit HF feedback noise from the welder.
tweake,
Oct 8, 7:58pm
has it got HF ? (assuming its even an AC welder).
johotech,
Oct 8, 8:08pm
Just goes to show how much notice people take. There are plenty of electrical equipment that have metal parts which aren't earthed, and they don't need to be earthed.
Your skillsaw or drill, will have metal parts but they won't be earthed and don't need to be earthed.
They will be either double insulated, or they will be marked as "Class II". Does it say Class II?
Class II equipment may be provided with an earth connection for purposes other than safety, this earth connection is referred to as a functional earth (FE). Functionally earthed parts are double insulated from live parts.
I would still be asking the supplier to give you the Supplier Declaration of Conformity for the product.
budgel,
Mar 10, 9:58pm
I will do that.
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