32amp wiring question

[johnna]

Hi everybody, first post!
I've used the search function and have gathered a fair bit of info, which leaves me looking for a little confirmation before I engage someone to do the job.
I have recently bought a powerful Arc welder form Germany. I have removed the Schuko plug and have replaced it with a 13amp fuse three pin item. The Welder fires up and will weld, but blows fuses and trips the fusebox for fun!
I use the welder in my garage (built into the house) and the existing sockets in there are upon the downstairs ring. Even when the welder is turned right down, it trips the protectors out.
Next to the red trip switch for the downstairs ring is a 'Spare' red trip switch upon my fuse board. All of this section is RCB protected. The house is only 12 years old by the way...
Also, the wall the fuse box is upon backs onto the garage wall.

So, is it feasible to have an electrician install a 32amp socket within the garage, with a short length of thick meaty supply cabling running through the wall to this spare 32amp trip switch in the fuse box?
I'd be keen on doing a lot of prep myself, such as drilling the hole through for the wiring and even feeding the cable through it, so the electrician need only wire it up, inspect the job and record his satisfaction.

Are my plans workable?

Thanks in advance.

 

[JohnD]

You have not said what are the power requirements of your equipment.

Read the maker's documentation and tell us.

 

[ban-all-sheds]

Schuko plugs are rated at 16A.

16A will not blow a 13A BS1362 fuse or trip a 32A breaker - are you sure you've not got some other problem?

 

[Adam_151]

If the manufacturer has supplied the welder with a schuko plug, then that would seem to indicate that it requires no more than 16A (unless the machine was second hand and a previous guy bodged a plug onto it?)

While bad practice, 16A shouldn't blow a 13A fuse!

In a german house, I'm lead to belive that shuko outlets would be installed on radial circuit protected by 16A BSEN 60898 C type MCBS


EDIT: Grr, too slow!

 

[johnna]

Thanks for the replies chaps!
This is the item I have bought, brand new:

http://cgi.ebay.co.uk/ws/eBayISAPI....m=370031526048&ssPageName=STRK:MEWN:IT&ih=024

"Model Electric welder BESG250
Mains supply 230 ~ 50 Hz
Protection class IP21
Input capacity 3.7 kW
Fuse 16 A
Welding current (90- 250 ) A
Diameter of electrode (2.5- 4) mm"


All of the power requirements should be stated there. The hand book is in German only.

I have read that the electricity supplied in Germany is non-polarised. Initially when I wired in the plug, it tripped out the fuses as soon as the welder was switched on. So I stripped the plug and reversed the two feed wires. The wires in the plug are Beige/Brown and Terracotta/Brown. The Earth is Green/ Yellow.

I have also read elsewhere that welding equipment of this type often trips the power supply unless uprated. But then again, you do read a lot of tripe from some sources!

I have a 230~110v transformer pack (for site use) and when the welder is wired to this it does not blow any fuses, but it also won't create enough of an arc to melt the rod.

 

[JohnD]

The thing that trips, is it the 32A MCB? Or the RCD?

What other loads are on the circuit you are trying to use?

 

[johnna]

I think initially it was the big RCD- but my wife reset it!!! (When the plug seemed miswired).
Since then, it has been the 13A fuses in the plug and in the heavy duty short extension lead I have as well as the MCB for the 32amp downstairs ring.

The short extension lead has been sturdy enough to run my mig welder.

 

[Space cat]

I think initially it was the big RCD- but my wife reset it!!! (When the plug seemed miswired).

If it really was the RCD, this points to earth leakage somewhere inside the welder. By reversing the wires in the plug you moved the leakage point closer to the neutral end and thus reduced the leakage current. This does not alter the fact that it's faulty.

Putting it on its own 32 amp breaker might not help. Does it trip the existing breaker when there are no other significant loads on the circuit? If it does then it will also trip the spare one - and it shouldn't!

 

[ban-all-sheds]

By reversing the wires in the plug you moved the leakage point closer to the neutral end and thus reduced the leakage current.

I'd be interested to see a more detailed explanation of this, complete with diagrams showing fault path impedances and current flows...

 

[SeanT]

Bearing in mind that the welder is basically a transformer, I'd say that's possible....

 

[ban-all-sheds]

If you linked the N&E pins in a plug, that would be the equivalent of moving the leakage point all the way to the neutral end. Are you saying that a plug with N&E linked wouldn't trip the RCD?

 

[BS3036]

Yeah, but that is a zero ohm fault. The original premise might work with, say, a 6500 Ohm fault to cpc. If it's near the phase end it will trip the RCD, if it's near the neutral it won't.

 

[Space cat]

I'd be interested to see a more detailed explanation of this, complete with diagrams showing fault path impedances and current flows...

I don't think I can upload diagrams from here so I'll try a written explanation.

Consider a simple resistive load, like a heating element, connected from live to neutral in the usual way. Now add a leakage path from some point on the load to earth. The leakage current will be equal to the potential difference between the leakage point and earth divided by the leakage resistance.

If the leakage point is near to the live end, the PD will be big and the leakage current may trip an RCD. Now reverse the live and neutral connections to the load. The leakage point is now near to the neutral end so the PD across the leak is much smaller. The leakage current is also smaller, maybe so small that the RCD doesn't trip.

I don't know anything about welding except that the arc voltage ia lower than the mains voltage - and so there's probably a transformer involved. A leakage path may exist between the innermost layer of the windings and the (earthed) core.

 

[johnna]

So the welder is faulty then?

I am experienced and handy enough to chase down an earthing fault in an electrical appliance, but with this being out of the box I never anticipated that I may need to.

 

[plugwash]

If you linked the N&E pins in a plug, that would be the equivalent of moving the leakage point all the way to the neutral end. Are you saying that a plug with N&E linked wouldn't trip the RCD?

It will probablly trip it because the fault path has such low resistance so even a very low voltage can drive enough current to trip a RCD.

On the other hand if you put say a 5K resistance between live and earth it should trip the rcd. If you put that same 5K resistance between neutral and earth it probablly won't.