I have been setting up my new chinese tig welder tonight and am a little confused about the casing earth connection on the back of the machine ( i assume others have this too??).

The instructions say to connect it to ground with 6mm cable. Is this really necessary and if so how have you done it?

Cheers

Check if the plug has an earth. IT may just be an extraneous earth, which i wouldnt be overly worried about if you have an earth in the plug, though i think i would take the covers off and make sure the thing is earthed properly.

If its anything like most of the Chinese crap that comes over here it will probably be a death trap. They get thier CE stickers off eBay.

Steve

Well, my piece of 'Chinese crap' has lasted at least 3 years now in a fairly nasty climate, with some fairly heavy abuse. You won't be buying any 'cheap' inverter based welder unit these days that's not been made in China. 'Made in UK', or made anywhere else for that matter, stickers are pence by the hundred!


The extra earth lead is supposed to stop any RF, or transmitted interference. You'll find that the website for the big blue machines and the other big name makes recommend the same earth lead for the welder frame.

Cheers,
Nev.

I'm sure Mr.Whippy, Interestedparty, Britishtrident et al will now come along with a totally opposite view and explanation.

[Edited on 19/2/11 by Neville Jones]

Nowt wrong with my group buy one and it's done a lot of work some of it at max power as well.

Does the earth need to go to the same earth as the plug or should it go to another earth or does it not matter?

(used to be a roadie when i was little and can't tell you why but everything was earthed at the same point to stop 'earth hum'.

Your earth will go to your work bench from the case to stop HF interference, although they are not always needed. Sometimes you see a spark jump from the tungsten before the button is pressed on mine.

Thanks for the responses! I have had a good go over the weekend and am very happy with the welder! Going to cut a pile of bits this week to have a really good practice on.

I did check earth continuity between case and plug pin, all is fine.
I haven't grounded the work piece yet, is it common practice to ground the workpiece to the welder earth or should it be separate?

Hi, I only joined the Forum recently and just noticed the post. I repair Chinese TIG Welders and Plasma Cutters and hope I can give you some technical information which might help.

The earth stud on the back of the machine is directly connected to mains earth in the plug and to the case of the machine.
The mains power connection to the front panel terminals is through high frequency transformers so there is no direct contact between the two circuits. Due to the transformer construction only the high frequency inverter power will couple through these devices, the 50Hz mains supply would just get shorted out by them.
The two output terminals which have the welding potentional between them normally both 'float' either to a positive or negative value of the welding voltage with respect to mains earth.

It would be possible under an extreem and unusual fault condition (like an internal fire) for the two output terminals to connect to mains live potential taking the welding electrode and earth clamp to the same voltage without blowing the primary fuse or RCD. With a fault of this nature it could happen without the torch switch activeated.

If the parent materials (components being welded) are connected to the stud on the back of the machine it ensures that under this type of fault condition the external safety devices will operate to protect the operator. The cable needs to be the same cross section as the mains supply connection to the machine.

I would point out this is applicable to almost all inverter based welding and cutting machines, not just those of Chinese origin.

Of more concern; I have repaired a number of Chinese Welders and Plasma Cutters that only have a two core mains supply lead, no mains earth connection has been provided. This would present a much greater potential hazard than not using the earth stud connection. If you have one of these it is essential for your safety that it is fitted with a proper mains cable with an earth connection. Replace the mains cable with a length of appropriate 3 core lead and connect the earth wire firmly to a clean part of the chassis. I will post detailed instructions of a modification if there are a number of people with the issue and need more help. It is not difficult to source the components and install and should be within the capabilities of most technical able Forum readers.

Hope it helps,

Mike