Help to Interpret a Regulation ?

[Evans Electric]

Job;

Requested to install a  32A  X  400V  welding socket  , outside wall of a plant hire workshop .  Occasional use of a Mig welder on lorries  or large plant.  

Question 

Looking at Reg  411.3.3   it appears that  (ii)  applies   .(Mobile equipment with a current rating not exceeding 32A for use outdoors )

Followed by exceptions  (a) & (b)  which say  for (a)  do a risk assessment   and (b)   stick a label on it .   

I'd normally go with an RCD  but am imagining the welder tripping it out .

Any views would be welcome .

 

[Sharpend]

Could you not use one of these? 

https://m.ebay.co.uk/itm/3-phase-16A-or-32A-5-Pin-CEE-RCD-Protected-Red-Socket-Hook-Up-Distribution-board/251559291581?

at least it’s local? 

 

[Sidney]

411.3.3 Additional requirements for socket-outlets and for the supply of mobile equipment for use outdoors

In AC systems, additional protection by means of an RCD with a rated residual operating current not exceeding 30 Ma shall be provided for:

(i)                  socket-outlets with a rated current not exceeding 32A, and

(ii)                mobile equipment with a rated current not exceeding 32A  for use outdoors.

An exception to (i) is permitted where, other than for installation in a dwelling, a documented risk assessment determines that RCD protection is not necessary.

So either fit an RCD or do a risk assessment. No provision for putting a label on it now.

Removing this line: (b) for a specific labelled or otherwise suitably identified socket-outlet provided for connection of a particular item of equipment. from the book has created no end of problems in the telecoms industry.

 

[Andy™]

fitted loads of RCD sockets for welders, not had any issues

https://www.toolstation.com/industrial-rcd-socket-ip67/p25246

 

[Evans Electric]

Could you not use one of these? 

https://m.ebay.co.uk/itm/3-phase-16A-or-32A-5-Pin-CEE-RCD-Protected-Red-Socket-Hook-Up-Distribution-board/251559291581?

at least it’s local? 

Thats what I'd be using  Sharpie  , just didn't know how welders would react with RCD.

fitted loads of RCD sockets for welders, not had any issues

https://www.toolstation.com/industrial-rcd-socket-ip67/p25246

Andy's reply has convinced me  ,  an RCD  Interlocked socket it is .  

 

[Geoff1946]

This string started me thinking about how the earthing of a big welder would be arranged. 

This led to recollection of an incident a few years ago, when a friend of mine, a professional metal-worker, momentarily put down his welding rod on an adjacent guillotine machine, and immediately burned out all its wiring back to the distribution board.

 

[Andy™]

This string started me thinking about how the earthing of a big welder would be arranged. 

This led to recollection of an incident a few years ago, when a friend of mine, a professional metal-worker, momentarily put down his welding rod on an adjacent guillotine machine, and immediately burned out all its wiring back to the distribution board.

welders output is seperate to the input so shouldnt be any issue in most circumstances. what probably happened there is the return from the welder was probably connected to bonded metalwork or another machines cpc etc. the electrode then being placed on the guillotine uses its cpc back to the welder

 

[Tony S]

This string started me thinking about how the earthing of a big welder would be arranged. 

This led to recollection of an incident a few years ago, when a friend of mine, a professional metal-worker, momentarily put down his welding rod on an adjacent guillotine machine, and immediately burned out all its wiring back to the distribution board.

Seen it happen many times with SWA, the cables armouring goes up in smoke. Usual culprit, the welder couldn’t be bothered to clamp the return lead properly.

 

[revjames]

Seen it happen many times with SWA, the cables armouring goes up in smoke. Usual culprit, the welder couldn’t be bothered to clamp the return lead properly.

Always fit outlets for welders with RCD socket. Usually 32a 5 pin. We did have a situation where the welder didnt place his return in the right place on one of the access ramps fot the ferries and totally wrecked the shielded cable and transducer feeding it.

 

[Tony S]

We couldn’t use plugs and sockets for the supply, all welders had to be hard wired in SWA. What we did do was run fixed welding radials from the set to various points around the plant. The problem would come with return currents using SWA armours.

 

[Sidewinder]

Also the design of welding sets has changed in recent years, all current models are isolating transformers, and the older type which are not where the welding return and the supply earth are common are considered dangerous and unsuitable for use.

 

[Evans Electric]

and the older type which are not where the welding return and the supply earth are common are considered dangerous and unsuitable for use.

 Ah !  Thats what made me question the use of an RCD .   Thanks Sidey. 

 

[apprentice87]

This string started me thinking about how the earthing of a big welder would be arranged. 

This led to recollection of an incident a few years ago, when a friend of mine, a professional metal-worker, momentarily put down his welding rod on an adjacent guillotine machine, and immediately burned out all its wiring back to the distribution board.

I can tell you all about this, being a properly qualified welder...

It is exactly as sidewinder has written.. The problem was with old welding sets..

For some reason, some idiot that wrote the british standard for welding sets decided that the secondary winding be earthed to the case of the set. Why this was, is beyond me at this time of night!!

Anyway, what would happen is this; You have two leads for welding, yes?? The lead to the rod holder, and the return lead [that is the proper name for it, NOT an "earth" lead] it is the WELDING RETURN LEAD.

Now, for safety reasons, you DID have a "welding earth". This was a lead that went from a good earth, say like the frame of the factory, to the "job", the thing you were welding. This was to stop the job going up to welding voltage, [relative to the ground it was stood on etc] which was usually 80-100V in them days and also for safety in case say the lead of a drill etc got squashed.

What the problem would be is this.. Picture this.. The secondary windings are earthed to the frame of the welder.. The welder is then earthed back to the MET. The job you are welding is ALSO earthed to the frame of the building, which is also bonded to the MET.

Mr welder forgets to connect the welding return lead, sticks in his 6 SWG iron powder rod and off he goes at 400A...

Ooer.. The current path now [with the return lead missing] is from one end of the secondary winding, down the welding cable, down the rod, across the arc gap, through the workpiece, down the "welding earth" to the frame of the shed, through the bonding cable that runs from the shed frame to the MET in the DB, back down the circuit wiring CPC to the welder socket/isolator whatever, down the welders supply lead, back to the case of the welder , which some dumbo decreed be connected to the other end of the secondary..

Result?? You burn out the entire earthing arrangement for that entire circuit back to the board, AND possibly many other circuits too, AND the bonding arrangements for the entire factory...

Apparently, the use of "welding earth leads" is now discouraged.. Something to do with TNCS perhaps????

Anyway, if a welder trips an RCD there is something wrong with it, so do not worry about that, AND, if you DO come across an old welder where the secondary is bonded to the case, the thing should not be used...

john..

 

[kerching]

@apprentice87 it just goes to show you can prove anything with facts!

excellent post

10/10

V.G.  

 

[apprentice87]

Thank you!!

john..

 

[Evans Electric]

Its a 10 from me too  as I was basing my RCD query  on "old" welders  ...of which I am more familiar .  

 

[apprentice87]

Ok, here is one for all you proper electricians to ponder over..

The RCD compares what goes down the phase conductor and compares it to what is flowing in the neutral. [Given that this is the case then, God knows how three phase ones work as neutral current could vary from nothing to lots depending on phase loading..]

Anyway, say the "old" sort of welder with the earthed secondary. At a guess, i would think they would be fine with an RCD, as that is on the supply side, but if mr welder left the welding return lead off, would not the old type of VOELCB trip instantly?? I presume it would depend on the impedance of the earthing arrangements and the magnitude of the welding current that flowed down them, [before they fried!!] Ohms law and all that!!

john..

 

[Evans Electric]

Back to my original query ,  although they are asking about a "welding " Socket  ... once fitted , say without an RCD , there is no control  over what else may be plugged in .  

This is a place where we have fitted some 13A  IP 65 sockets near the powerful  jet wash area   (  Hosing returning JCBs down)  The concept of closing the lids seems to escape them as they are regularly  snapped off  and discarded. :C    

 

[binky]

stick a label on it aying 'welder only, not RCD protected, do not use for any other portable appliances outdoors'  arse covered!  And / or fit a padlock.  I'm sure it will get ignored, but that puts the onus on the supervisors / safety manager, who you should also inform in writing that this is the case, so that is up to the company to manage the safety of this socket and t's use.

 

[Andy™]

stick a label on it aying 'welder only, not RCD protected, do not use for any other portable appliances outdoors'  arse covered!  And / or fit a padlock.  I'm sure it will get ignored, but that puts the onus on the supervisors / safety manager, who you should also inform in writing that this is the case, so that is up to the company to manage the safety of this socket and t's use.

or just stick in an RCD... if tit trips its usually because its faulty