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  1. #1
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    Default Why you shouldn't modify cables on welding machines

    We had a similar thread HERE //metalworkforums.com/f309/t202810-15-amp-plug, which sparked some interesting, yet poorly thought out discussion on changing 15A to 10A plugs on some machinery. I do a bit of this day-to-day, and can add some further value here to help educate as to the reasons why not to mess with your electrical equipment.

    Below is some details of, and further reading on why you should NOT modify electrical cables for plant and equipment- in this instance, I've modelled this reply off a welding machine example- which many of us may be able to relate to.


    Your welder has a data plate on it, and a few key bits of info- iMAX is the 'max current' the machine can draw when you give it the beans- a180A welder might top out at say, 25A current draw for a short peroid of time following arc initiation.
    Another important value on the machine's data plat is the iEFF or 'effective current' the machine draws. Consider this the average current at max machine output that it will draw, after the current 'spike' has settled. This is calculated by electrical engineers using a formula as long as your arm.

    In layman's terms, the machine draws current from the wall, the power point doesn't give it. A welder is just a gearbox for power - feed it 240V at 15A, and it will convert it into 'welding power' say, 12V, 170A for Stick welding, or 19V and 160A for MIG welding... or thereabouts- Ohm's law applies, but that's a whole different topic.
    This above information dictates which power plug and subsequent circuit the machine needs to be used on. Small welders may use a 10A plug and circuit, but are usually only food to 130A. Larger machines, up to about 180A can run a 15A plug. Bigger machines again, a 32A plug, then we move into 3 pahse power etc.


    So... On top of this all fits a whole raft of 'external' factors to the welder.
    1) There is an Australian Standard that electricians use to dictate wiring practices in home, workshops and other places. Things like calculated draw on a 10A circuit, what circuit protection is used (circuit breakers in the meter box), cable cross sectional area (conductor CSA) etc etc. This includes the 'single 15A GPO on a 15A circuit' rule. Circuit protection can and does fail under higher loads than they are designed for. Ask any sparky for some pics of burnt our CB's and be prepared to be shocked.
    2) Machine manufacturers need to abide by rules for the design of their machines- as designers they can be legally liable for faults in design which cause injury or death- this is the work health and safety piece, Graeme can probably give more info in this... As a result, point 3 applies:
    3) Machine certification by manufacturers needs to account for a proper input cable size (ie the conductor CSA) and a 'suitable plug' fitted to the machine to meet it's iEFF current draw under maximum output (read 'worst case scenario') conditions. This is a stipulation of certification for the machine as a compliant to AS 60974, and for the Regulatory compliance mark (RCM) certification you should be looking for in a machine when purchasing.
    As a result of this information, you'll start to see a number of machines in the 200+ amp range now be fitted with the big orange single phase (3-pin) 32A plugs...
    4) Workplaces using machines like this will also go thru a testing and tagging program, which amongst other things, checks that the plug and circuit is up to the task of the appliance. not doing so is bad news for a PCBU (person undertaking a business or undertaking) if there is an injury or death, and the law and precedence of cases will certainly see you dragged thru a court or worse.

    The whole idea of this is that the machine is engineered SAFE, meets standard, and the fitted plug is capable of safely working on the circuit which it is plugged into.

    ...with all this in mind, you could be a goose and run a non standard plug to make it work... but you'd also be tempting fate with multiple levels of engineering controlls being bypassed which are all there for your safety. Doing anything other than fitting it to a correct circuit is meddling with your safety and should not be done.




    So, standards and other boring stuff aside, the extreme, but not-too-improbable scenario could go something like this:

    An aspiring welder, Mr Richard Cranium, buys a nice new MIG welder, but blows all his coin on the machine, and is too cheap to get a proper power circuit installed for his 250A machine.
    Being a bit creative, Richard removes the 32A plug fitted to the machine, thus voiding his warranty with the manufacturer, and fits a 10A plug so he can use in the the garage alongside his beer fridge. The fridge is an old kelvinator from the 50's and has given the circuit a bloody hard time over the past 35 years of use, keeping the beer cold at 1 degree inside the shed that routinely reaches 45 degrees plus ambient during a hot summer (all the while Richard makes use of said fridge every half hour thru most of the weekend). As a result the wiring is old, and the insulation is heat damaged within the walls. The circuit board, installed with the house in the 1940's, uses ceramic circuit breakers and fuse wire, and unbeknownst to Richard, the previous owner of the building purchased and installed the wrong fuse wire for the shed circuit, a fuse which was well higher than what the wiring can handle.
    Keen to test out his new welder, Richard plugs his 250A welder into his 10A circuit, but not before moving it into his welding area with a 15m extension cord. 'Perfect' thinks Richard, as he reaches for some 12mm plate steel and unpacks his new spool of 1.2mm wire for his first test weld. 'I'll give her the beans!' he says as he turns the dial to 11 and proceeds his first weld... as his fridge compressor is busily working hard on the same circuit.
    With this, the conductors (wires) in the wall melt, and ignite- the circuit protection has not done its job, as it was a 50A wire installed by mistake. Richard now has an electrical fire on his hands, in the walls of his shed, and unable to be extinguished.
    The insurance assessors review the ashes of his house, and deny his claim. The manufacturer, who has all the certification for the machine in order, denies any liability or responsibility for the damages as a result of using the machine, as it was improperly modified.
    Richard then continues to live the rest of his days on skid row, needing to pimp himself out for small change to stay alive, with no house, job or immediate prospects. "If only I didn't burn the house down" he mumbles to himself.


    Be smart with your power, and stay safe. Don't be like Richard.

  2. #2
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    Sounds like you are giving legal advice to who Richard could or could not pursue in this matter. I would avoid giving legal advice unless permitted by The Legal Practitioners Act.

  3. #3
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    I don't see it as giving advise, just a laying down of what COULD happen if you changed a plug on a machine.
    Kryn
    To grow old is mandatory, growing up is optional.

  4. #4
    BobL is offline Member: Blue and white apron brigade
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    Still trying to come to grips with what the old fridge has to do with anything?

  5. #5
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    I see your point. The same situation could happen even if he had a dedicated circuit if the incorrect fuse wire was used or any number of dodgy stuff was done.

    In the other thread I mentioned to change the plug from a 15A to a 10A. This is obviously dodgy but it's no better or worse than making up a 15A to 10A adapter extension lead. OK so it's better in the sense you can change it back and cover your dodgyness but in terms of the actual act, it's still using a 15A machine on a 10A circuit which is certainly not good.

    Last week we attended a fuse box fire at a well known automotive store. A hot day with many things running in the store. Turns out the board had been "upgraded" from 3 x 50A circuits to 4 x 100A circuits with no change to the wiring or other necessary "stuff" It didn't end well!

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  6. #6
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    I don't quite understand the example in the last paragraph either - if the wiring is in a poor state due to age, and the protective fuse for the circuit has oversized wire fitted, then *any* overload condition could cause a fire, there's nothing particularly special about a welder in that respect. Plugging 2 fan heaters into GPOs on the same circuit could achieve the same result.

    As for the insurance boogey man that seems so popular in these parts, I've heard from actual insurance assesors that unless there's a death involved, there typically isn't a forensic investigation to drill down the the precise cause and who may be to blame. House burns down, they just pay the claim.

  7. #7
    BobL is offline Member: Blue and white apron brigade
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    The legalities around fires are rarely cut and dried.

    We had a small fire (~ 1 BBQ burner size) in a uni lab at work. Lost of black smoke from burning plastic when a $20k chiller caught fire at 5am in the morning and a student working overnight saw the fire through a window but couldn't get into the lab as it was locked so he called security. The security guard arrived and looked around for a fire extinguisher but he missed the sign on the door to the lab that said "in case of fire use only [water mist] extinguisher inside lab near the door" and instead grabbed a dry powder extinguished from the corridor and put out the fire. In doing so the ammonium phosphate did $1.5m worth of damage to the analytical equipment inside the lab. The fire could have been extinguished with a fire blanket - also hanging by the door.

    The Lab was out of action for 18 months while a huge legal wrangle over who was to blame took place. In the end costs for equipment and operating losses were split between the manufacturer of the chiller (fires being reported in these chiller units around the world), the supplier of the chiller (who knew the chillers had probs), the employer of the security firm, and the Uni's insurer. I heard the insurer and suppler then sued the manufacturer - I have no idea if they got their money or not.

    The silly thing was we never wanted to have the chiller inside the lab in the first place and we wanted to locate it in a weather proof box outside the building but Admin said it would spoil the (red brick and exposed concrete 60's) architecture of the buildings. What a flaming joke.

  8. #8
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    Yea, dry powder extinguishers are great at putting out Class A, B and (E) fires but they create a massive mess and can actually cause more damage and higher cleanup costs than the fire itself.

    Certainly for around the home a fire blanket are the best. I also have a vapourising liquid extinguisher which are awesome too.

    It's not unusual for people in the heat of the moment to make a situation worse not better. I think it would be harsh to blame the security guard though without knowing what training he had and seeing his induction program before he started working at the establishment. People are less likely to read signage during stressful situations.

    Luckily for me, any damage done by firefighters during firefighting operations is deemed (by act of parliament) to be fire damage!

    Having said that, we make sure that specific risks in our area are understood and we know what extinguishing media can and can't be used. It's not very professional if we attend a fire and cause $100,000 damage when the fire damage is maybe only $50,000.

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  9. #9
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    Quote Originally Posted by lamestllama View Post
    Sounds like you are giving legal advice to who Richard could or could not pursue in this matter. I would avoid giving legal advice unless permitted by The Legal Practitioners Act.
    So you have to be Geoffrey Robertson QC to pose a hypothetical around here? Dream on buster...

    Quote Originally Posted by BobL View Post
    Still trying to come to grips with what the old fridge has to do with anything?
    Besides the Fridge being the source of the most essential workshop consumable, It is an example of what may cause a compromised circuit, also adding additional heavy load to the circuit. In actual fact it could be a number of other appliances, or in severe cases, just one appliance with a large power requirement well and truly above the capacity of the circuit.

  10. #10
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by simonl View Post
    It's not unusual for people in the heat of the moment to make a situation worse not better. I think it would be harsh to blame the security guard though without knowing what training he had and seeing his induction program before he started working at the establishment. People are less likely to read signage during stressful situations.
    I'm pretty sure he was trained and I don't think it was that stressful - It's not like the whole room was on fire.. But I don't blame him that much. If anything I want to blame the ning-nong administrator who wouldn't let us locate teh chiller outside.

  11. #11
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Commander_Keen View Post
    So you have to be Geoffrey Robertson QC to pose a hypothetical around here? Dream on buster...
    Besides the Fridge being the source of the most essential workshop consumable, It is an example of what may cause a compromised circuit, also adding additional heavy load to the circuit. In actual fact it could be a number of other appliances, or in severe cases, just one appliance with a large power requirement well and truly above the capacity of the circuit.
    The way I read it the fridge just colours and pads out the story and, "all the while Richard makes use of said fridge every half hour thru most of the weekend" implies Richterd is an alky and all round general lower life form, but IMHO it would be deemed irrelevant by most magistrates.

    A fridge is still handy equipment for my operations but not for alcohol as I rarely drink it. However, I do use it for storing certain chemicals, adhesives and dog bones/food.

  12. #12
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    Quote Originally Posted by KBs PensNmore View Post
    I don't see it as giving advise, just a laying down of what COULD happen if you changed a plug on a machine.
    Kryn
    Like the other thread I still call rubbish. The standards are not based on engineering principle. Lets say Richard Cranium instead of buying a welder has a four port 10 amp GPO outlet installed., his beer fridge is churning away, then in the same GPO he decides to cook some food, so plugs in one of those portable ovens to cook some fish and chips. Then he still has two spare ports on the same GPO, so he plugs in the kettle to boil some water. He is also a bit of a preener so decides to plug in his hair dryer and do his hair.

    He is pulling far far far more amps then if he had his welder plugged in with the adapter, but that is all fine and dandy. His shed burns down and the insurance agent see's all the items plugged in and says. Don't worry, that is acceptable under the electrical guidelines, here is your money.

    I am not saying it is fine to do it, I am saying the rules are not based on engineering principle. What the rules probably say though that all wiring must be able to handle the amperage of the fuse. My shed the single 15 amp GPO and the six ten amp GPO's both use an identical fuse, that being 20 amps.
    Gold, the colour of choice for the discerning person.

  13. #13
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    One point to further muddy the waters is that many welders come with a 15A plug attached from the factory when their actual power demand is closer to 25A. They also have a nice little sticker attached to the power cable stating that to achieve maximum output a higher capacity circuit must be used. Who reads this and abides by it for a start and secondly how will joe public know when the upper limit of the 15A supply has been reached?
    It is unlikely that anyone will put in writing the permission to use a 10A to 15A "naughty lead", however we all know there are an awful lot in service out there and you will find that the wiring used in a 15A lead is thinner than the wire used to connect the 10A GPO in most cases.
    Those wishing to use such adaptor leads will need to make their own minds up. I would also add that there are far more likely causes of an electrically caused house fire than the 10 to 15A lead.

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    Quote Originally Posted by Commander_Keen View Post
    So you have to be Geoffrey Robertson QC to pose a hypothetical around here? Dream on buster...
    The person who modified the fixed wiring design by installing incorrectly sized fuse wire is the person responsible for this fire, yet you try to apportion 100% of the liability in Richard's direction . The more likely outcome is Richard gets his insurance or most of it paid out (because he didn't create the dangerous situation in the fixed wiring of his house) and gets a house with modern wiring and at some time in the near future realises he can't be bothered with his welder tripping the circuit breaker so he gets himself a 32A outlet installed.

    A scenario as realistic as the original proposal is that he decides to emigrate to NZ where he can do his own electrical work using the same AS/NZ standards and participate in a system that kills less people per capita through electrical faults than does our highly regulated system. This would the give him the option of correctly installing his own 32A outlet and associated circuit thus avoiding reliance on substandard work done by others or the motivation to do dodgy workarounds because he isn't legally allowed to do the right thing.

  15. #15
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    Quote Originally Posted by .RC. View Post
    The standards are not based on engineering principle.
    Where did you get that info?

    Quote Originally Posted by .RC. View Post
    What the rules probably say though that all wiring must be able to handle the amperage of the fuse.
    AS3000 pretty much says that.
    Chris

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