Info on a dedicated circuit for a welding machine required.

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That statement was an error regarding the use of an RCD in the garage and part of that statement was implying the question of what size circuit breaker is required for the feed to the garage (to protect the cable, but I shouldn't have to explain that really just to show how much knowledge I have about RCD's and circuit breakers) In the following replies I covered that I recognised this error. This error by me was purely because I had it in my head that every CCU requires an RCD purely because I know that the regs say that all wiring in walls needs one, I had forgotten that there was no need for another one because there is one in the CCU that feeds the garage CCU.
I hope that this puts a line under this thread now and we can all put it down to one big misunderstanding.
DIY or DIE, Peace out.
 
bernardgreen said:
So out of interest can you tell us what the qualified electrician told you was necessary fopr a safe and compliant installation ? After all we might learn something that we need to know.
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I'll post the solution later, got to go.
 
Isol8or said:
I know that the regs say that all wiring in walls needs one
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That's not quite what they say. Even where buried less than 50mm deep there are means of avoiding RCD protection if desirable. It is likely to cost more to do it this way though.
 
bernardgreen said:
Most DNOs seem to consider 1kW or above as a large load when discussing welders and motors due to the large inrush currents and the effect they can have on the network.

Read more: http://www.diynot.com/diy/threads/wiring-diagram.467863/#ixzz4N2cCUcpV
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I note it is an inverter welder so the in rush does not really happen. This was the big advantage with the small inverter welder you could use it with 13A plug with 16A B type MCB, OK yours is bigger but same applies the in rush is so small you can forget about it.

The inverter welder also has other advantages it feels like DC even when it's an AC output so smooth, it does have problems with wave form distortion like many other inverter devices but not in rush.
 
ericmark said:
I note it is an inverter welder so the in rush does not really happen. This was the big advantage with the small inverter welder you could use it with 13A plug with 16A B type MCB, OK yours is bigger but same applies the in rush is so small you can forget about it.

The inverter welder also has other advantages it feels like DC even when it's an AC output so smooth, it does have problems with wave form distortion like many other inverter devices but not in rush.
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Thanks for your input, I had a hunch that the inverter manages this in some clever way. So do you think I'll be ok with a 16A commando socket and a 16A MCB type B then?
 
bernardgreen said:
In which case the give away dips in neighbour's lights are unlikely to happen so the DNO will probably not become aware
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Again interesting info but why would that happen when the supply to the house is much larger than the in-rush of current being drawn?
 
Isol8or said:
supply to the house is much larger than the in-rush of current being drawn?
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It isn't. With transformers and motors the inrush current can be several times the rating of the fuse in the supply to the house, ( hint, use of a slow to act MCB ).
For transformers this overload lasts for less than one cycle of the mains ( 20 milliseconds ).
For motors this overload exists while the motor is accelerating up to normal running speed, it reduces as speed increases.
Welders using transformers ( as opposed to invertors ) will produce a peak overload current every time the arc is struck and also when the arc splutters.
The effect of a welder with an invertor is dependent on the type of invertor.

The in-rush current causes a voltage drop along the cable from the substation to your house, that voltage drop will affect all the houses supplied by that cable. Those close to the substation will have only a small drop, those further away and closer to the point of over load will have larger drops.

An example . Newly installed 1.5 kW table saw in a domestic garage about 3/4 mile from the substation, when the saw started the voltage drop at the neighbours was about 10 volts. It took about one second for the voltage to return to normal. Neighbours reported the fault of dippling lights to the DNO. The DNO investigated suspecting a cable fault. The saw could be heard starting when the lights dipped. The owner of the saw was immediately "requested" by the DNO not to use it. He ignored the request. DNO increased the pressure. possible threat of disconnection and eventually he converted the motor to a soft start system
 
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