MIG Welder- is a Seperate Supply Circuit Needed?

CAWORK · 27 May 2009

HI

My father has just bought a combination as/no gas MIG welder and am a bit confused about the supply.

The instruction book in the begining says Model pcmig135/09 circuit breaker 30A.

For Welding currents up to 65Amp (lower settings) a 13amp plug may be used and for above (higher settings) that a 32amp plug and socket on a seperate 30amp fused circuit is needed.

It has power settings from 0-6.

What would be the best way to go about this? even though it may be used from a 13a plug i have seen some badly dameged ones from welders before (on this site I think?)

Also ring is RCD 30ma protected and other circuits 100ma protected, will this be a problem?

Cheers

bogbasher · 27 May 2009

The best way would be to use a 32 amp plug on a 30 amp fused circuit.

CAWORK · 27 May 2009

OK

But would this actually be protected by a fuse or would a 32 amp mcb possibly type C, D etc be ok? (to install a seperate switchfuse, next to the CU, for the industrial type socket mentioned is not an option due to lack of space)

Also is RCD tripping possible since I have heard welders have a reputation for doing this?

cheers

flameport · 27 May 2009

CAWORK said:
For Welding currents up to 65Amp (lower settings) a 13amp plug may be used and for above (higher settings) that a 32amp plug and socket on a seperate 30amp fused circuit is needed.

If the manual states that, it is dangerous and irresponsible. If the appliance requires a 30A circuit, then that is what it must have.

Putting a 13A plug on and only using the lower settings is the same as connecting a high powered electric hob to a 13A plug and only using 1 ring at a time. Fine until someone forgets or doesn't know about the restriction, and uses all of them, melting the plug, socket and whatever else was in the vicinity.

The RCD shouldn't be an issue - unless the welder is faulty.
This welder won't be going on the ring anyway.

If you also have a 100mA RCD, this suggests a TT supply, so you have to have the RCD regardless of what is connected.

RF Lighting · 27 May 2009

Yeah an MCB would be fine.

It would be best to be either type C or type D, but you need to ENSURE the earth fault loop impedence is low enough for these devices.

Both of them are required to have a circuit Zs lower than the permitted incomming Ze for a TN-S supply.

The RCD shouldn't be a problem unless the welder is faulty, but I couldn't say for sure with such a big inductive load and EMF etc...

CAWORK · 27 May 2009

If the manual states that, it is dangerous and irresponsible. If the appliance requires a 30A circuit, then that is what it must have.

This is exactly what I was thinking. I'm also not sure if it actually says which setting is the maximum for a standard plug settings 1-6. The machine is marked 30-135 amps i presume the output/
welding current?

Powrcraft combination gas/no gas MIG welder purchased from Aldi.

Yes I was a bit wary of connecting it to a 13 amp plug.

TT supply all sockets 30mA, lights, cooker and immersion 100mA T/D

Any other advice or suggestions?

Cheers

RF Lighting · 27 May 2009

As it is a TT supply, you HAVE to have the socket protected by an RCD.

It would be better off IMO protected by the 100mA TD RCD.

It will be OK to protect this socket with a type C / D MCB, as the RCD will take care of any faults to earth.

ban-all-sheds · 27 May 2009

flameport said:
Fine until someone forgets or doesn't know about the restriction, and uses all of them, melting the plug, socket and whatever else was in the vicinity.

Should it be possible to draw enough current through a 13A fuse for enough time to do damage like that?

RF Lighting · 27 May 2009

I reckon if you had a sustained current draw of say 15A, it's going to take a while for the fuse to pop, whilst everything gets toasty warm.

bogbasher · 27 May 2009

From experience I can say it is easily possible to use them for long enough to cause a fault on a circuit not rated for it.

CAWORK · 27 May 2009

Cheers everyone

The language used in the instructions doesn't seem good either since in some places it says 'live' an 'neutral' and others 'positive' and 'negative' (yes, referring to the mains supply conductors!).

Despite it been ok on smaller loads, like I said I have seen some pictures of a 13 amp plug and socket charred terribly after been used to supply a welder.

ban-all-sheds · 27 May 2009

RF Lighting said:
I reckon if you had a sustained current draw of say 15A, it's going to take a while for the fuse to pop, whilst everything gets toasty warm.

Warm yes, but according to BS 1363 not warm enough to suffer any damage after 14A for 8h...

ericmark · 28 May 2009

I did look at the Aldi Advert and these

welders have very little to say what they are. I would not expect it is a switch mode inverter at that price just a transformer and rectifier.

But I do see it comes fitted with a 13A Plug and I would think if there was a problem with this arrangement the Aldi would have a major problem.

Most welders have an output voltage of 25 volt plus 1 volt for every 25A so at 130A output volts around 30 volt. So 17A is likely draw at 230V this is not much over the 13A and one tends not to weld for long stretches so would likely work OK with 13A supply.

Since we tend to jump 13A, 16A, 32A, 63A in plug sizes I can see why it would recommend a 30/32 amp supply. However many of these welders used to have a 16A plug with a converter to 13A and because over the 3500W (I think that was old limit) they could be used on building sites with 230v.
However with 17th Edition the rules changed. 704.410.3.10 now states up to and including 32A so it seems there 16A plug with converter will no longer exempt them from 110v rule on building sites. So now no longer supplied in that way.
But I would think that very likely a 16A plug would work OK with a D16 MCB protecting it. Not sure how it would effect any guarantee though once you cut the plug off it?

ColJack · 28 May 2009

exactly how do you have a Metal Inert GAS welder without gas?????

CAWORK · 28 May 2009

But I do see it comes fitted with a 13A Plug

Mine didn't!

It just had the flex end stripped with copper crimped over the bare ends like appliance manufacturers often do when fitting plugs.

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MIG Welder- is a Seperate Supply Circuit Needed?

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