Thread: 15amp welders on 10amp circuits

Every joint in a conductor increases resistance and is another chance for a dodgy connection, which could cause excessive heat many GPOs away from the one you are over loading, maybe under the bed in anoter room.

The 'go/nogo' testing criteria for a multiple 10 amp GPO circuit vs. a single 15 amp GPO circuit are identical.

There is no different testing regime used due to the type or number of GPOs connected to a circuit, as in the end, a circuit with a 10 amp heater, a 4 amp plasma TV and a 1 amp laptop is going to be pulling just the same amount of power through any dodgy connections as a 15 amp welder.

As long as the circuit is correctly wired, has less than 0.5 ohm earth resistance, greater than 1 megaohm insulation resistance, and (optionally) a maximum fault loop impedance of less than 3.59 ohms for a type B 16 amp circuit breaker, it passes.


Any alteration to the fixed wiring has to be done by a licensed trades man by law.

We've already assumed that this regulation (which is unique to Australia, I should add) is being ignored by our price sensitive individual, as it is ignored by all those Australians who purchase powerpoints, lights, conduit and T&E from hardware stores like Bunnings. (be honest here, you don't seriously believe that sparkies are walking into bunnies in droves and paying $15 each for powerpoints, $14 for circuit breakers or $320 for a roll of 6mm T&E, do you?)


Sticking or tying up the circuit breaker will only hold up the toggle, the innards will still trip and break the circuit.

Sigh. That's an example only - replace with your choice of 'self tapping screw rammed through the workings' or 'old coathanger wire as a shunt'.

Hi silentC,
You are quiet correct and I am horrified at his attitude. We are wasting our time trying to point out the error of his ways and just hope the innocents who read this thread take our concerns on board.
Some of the figures he has been throwing around in his bull dust baffles a brains justifications are not all that out the rating for a 2.5 circuit is 16 amps when protected by a fuse and 20 amps when protected by a circuit breaker but that gets de-rated to 16 amp when the cable is covered by insulation that is why they change your breaker when you have wall cavity insulation installed and was also one of the problems with the disastrous insulation scheme.
Just to take away some of the anonymity I had 47 years in the electrical trade in 4 countries before retiring and still hold a current ACT licence.
Regards

Originally Posted by A Duke

Just to take away some of the anonymity I had 47 years in the electrical trade in 4 countries before retiring and still hold a current ACT licence.
Regards

So Hugh, you would then be one of those who actually knows what he is taking about, as opposed to those who only think they do.

Originally Posted by A Duke

Hi silentC,
You are quiet correct and I am horrified at his attitude. We are wasting our time trying to point out the error of his ways and just hope the innocents who read this thread take our concerns on board.

Let's be clear - nobody is encouraging anyone to do anything. It's already been made amply clear what the rules and regulations are, and many warnings of possible consequences have been provided.

However, rules and laws aside, there is also the reality of what many people do, and it is useful to discuss and recognise the *real* risks posed.

As it stands, one can easily (and legally) apply a load in excess of 10A to a dual 10A socket by plugging in 2 loads. Now that socket that may have many looped sockets between it and the breaker, yet we don't seem to fear our walls or roof space bursting into flames.

So what's the difference with plugging in a single 15A load into the same socket?

Replying to woodworkforums.com/f160/15amp-welders-10amp-circuits-126819/index4.html#post1235703


There are plenty of people here....

And there are plenty of people here who don't have the space or spare cash to be able to purchase a 3hp tablesaw, let alone get it installed, so they make do with what they can scrape by on.

I mean - does your saw have a Saw Stop doodad to stop you chopping a finger off, or a power feed to prevent kickback injuries - or was that a little too much to pay to prevent such accidents and you did a price/safety tradeoff? But surely those features would be part of doing it properly, no?

One person's $350 'do it right' install cost might be competing with someone else's brake pads for the car, braces for the kids, or other non-leisure activity needs.


The other thing about your suggestion is that, firstly it's illegal (in NSW, Vic and ACT that I know of).

It's illegal in all states and territories of Australia. Yes, this does go so far as to include "undoing the screws a bit" - that's just as illegal as taking the whole point off the wall or undoing the terminal screws - it's all "interfering with fixed electrical assets", etc etc etc. (Interestingly, Australia is the only first world country where homeowners are not allowed to do their own electrical work in some way. Australia also has the highest electrical fatality rate.)


Secondly, fitting a 15a point to an existing 10a circuit..

Let's dispel the idea that the power point has an influence on the circuit rating. Circuit rating is determined by the size of the breaker, which in turn is dependant on the size, insulation and installation of the wire used.

The minimum nominal cross sectional area of wire for a socket-outlet circuit is 2.5mm, and when you have 2.5mm T&E, your protective device (circuit breaker) rating is 25 amps (wire in air), 20 amps (wire partially surrounded by thermal insulation), or 16 amps (completely surrounded by thermal insulation). (Table C5 AS/NZS 3000:2007. Yes, I do have a copy. Also 3008, 4417, 4836, 2225, 3012, 3018 and others).

In the case of replacing a standard 10 amp GPO with a 15 amp one, you are replacing a GPO that can have one (or two or four or five) 10 amp socket outlets (potentially 50 amps concurrent load) with a single outlet that will be connected to a 15 amp load.

At this point you can say "ah, but people should know not to plug in more than 10 amps at a time on one of those multi-powerpointed GPOs", to which I would reply "Yer. Good luck with that".

Taking the case of a double power point in a kitchen: it would be quite possible to plug in two appliances such as kettle and a toaster and be drawing 17 amps or more through that double GPO connection.

Tripping (or at least, instant tripping) only occurs at 4 times the rated current for a type B circuit breaker, so you'd probably be able to use this kettle/toaster circuit frequently without any tripping as the cycle time of boiling a kettle could be shorter than the time required to trip the breaker at (say) 120% of capacity - which might take as much as 5 minutes.

So it's not like your 15 amp point it is unduly stressing the circuit or overloading it in a never before imagined way.


I don't think there's any justification for advising someone to do it, even if it seems logical to do so to an anonymous layperson on the internet.

If you read what I have written, I don't think you'll find I've said "Go and do this" - I've just provided options to help people clarify the issues so that they can make an informed choice.

If the alternative is that they go off and use even less-safe approaches (going from a connection that involves "wire protected by circuit breaker/lead designed for the appliance load" to "wire protected by circuit breaker/something of lesser capacity and unprotected/lead designed for appliance load") what would you suggest?

Silence? That's worked real well for the fatality rate compared to the rest of the world (not).

Ok - my official, this is what you should do, advice for this thread is: "Work harder, get a job earning $500,000 or more per annum and just hire someone to do your woodworking/metalworking for you. You'll save money by not buying tools and not needing garage space for said tools, you won't have to waste time learning how to use them, and the only safety concerns you'll have is putting your back out when you pick up your wallet."



I think you'll find that is not typically the case. The one my table saw is on has a 20a breaker for example.

A more thoughtful breaker selection includes consideration of load type as well as the other factors, which are not covered in Table C5 (which is basically the "Dummies Guide"). There's a good dozen pages on load groups, maximum final demand, circuit length, thermal derating and so on.

I'd say $360 is not a great deal of money. Suck it up cheapskates.

I don't know what is wrong with a bloke who will spend $40000 plus on a new car for his missus and kids to turn into a mobile rubbish tip, spends only $300 on a welder for himself and then wants to file down an earth pin on a 15 amp plug.

Some reprioritisation is needed.

In other words, grow some nuts.

If she is going to leave you because you want a new 15 amp circuit for your welder, she will eventually find another excuse anyway. You'd be better off finding out now.

Geoff,
I hope I do.


Rusty,
You want me to commit myself to what I would do?
As a stop gap or if I was only borrowing a 15 amp device I would make up a short converter lead.
Why because every time it was plugged in anyone would know they were doing a naughty. Changing the socket on the existing circuit Never. Filing the pin no. Changing to a 10 amp plug don't think so but the user could read the label (as the original poster did) and know what they were doing. If I was to use it regularly I would install a dedicated 15 amp circuit but then I have an advantage over most thats why I pay the fees to keep my licence up.

Read this in conjunction with the forum disclaimer. and consider it includes me

Originally Posted by A Duke

Some of the figures he has been throwing around in his bull dust baffles a brains justifications are not all that out the rating for a 2.5 circuit is 16 amps when protected by a fuse and 20 amps when protected by a circuit breaker but that gets de-rated to 16 amp when the cable is covered by insulation that is why they change your breaker when you have wall cavity insulation installed and was also one of the problems with the disastrous insulation scheme.
Regards

If I could just clarify what is meant by the above statement I could probably rebut it:

Does "Some of the figures he has been throwing around in his bull dust baffles a brains justifications are not all that out the rating..." mean:

1) Some of the figures....are not all that out (meaning the figures are largely correct).
2) Information sourced from AS/NZS3000 is largely correct/incorrect?
3) His repeated reference to a 16 amp circuit capacity indicates that he is correctly using AS/NZS3000 to provide a simple 'worst case' scenario in assuming that a 2.5mm T&E power circuit is likely to be fully enclosed in thermal insulation for its entire length.

Now, I'll happily say "doing your own electrical work is illegal".

Drink driving is also illegal, and causes a few orders of magnitude more deaths than electrical accidents and is much more visible, yet people still do it.

Why would you assume that the people who are going to do their own electrical work will be stopped by a lack of Australian-relevant information?

If lucky, they will refer to a New Zealand D-I-Y guide, such as the one published by the NZ electrical regulator (you know, the NZ part of the AS/NZS electrical standards) where the differences are very, very minor. They may also use some of the English DIY guides, or, if really unlucky, some of the American ones.

But still, I'd be really interested how a 15 amp plug for a welder presents such an incredible escalation of danger compared to a double power point with a 10 amp kettle in one socket and a 10 amp fan heater in the other.

If I am having a massive brain-fart in my conceptual model, I'd love to be corrected.

Actually, I've just thought of a sneaky - and possibly vaguely legal - way of doing it!

Get two lengths of 10 amp flex, a 15 amp GPO, two 10 amp plugs and a large junction box. Mount the GPO on the junction box, connect a plug to each length of flex, and connect the other ends of the flex together at the terminals of the GPO. Plug the two plugs into a standard double outlet, plug the welder into the 15 amp socket....and....mwahahahahahah! Frankencable is born! (note. not serious. but interesting)

Originally Posted by A Duke

Why because every time it was plugged in anyone would know they were doing a naughty.

That's the point. They wouldn't. To 'them' it's just a short extension lead, and they'd probably think you were silly for not just changing what was obviously 'the wrong plug' on the appliance lead.

Remember:

• These are the same people who press on the "Click here to install our viewer software that lets you see the naughty nudie pictures for free!" button and get a PC full of bots and viruses. Twice.
• These are the people who top the oil up in their car all the way to the top of the overhead cam, then ask if its normal for a car to need four of those 5-litre containers of oil for a top up.
• These are the people who wipe the dust off the elements and controls of an electric heater with a very wet cloth, while the heater is still plugged in and live.
• These are the people who jam their aluminium ladder against the aerial mains connection point because 'it looks nice and sturdy'.
• These are the people who don't push the trailer coupling down till it locks because 'I thought that was what the safety chain was for'.
• These are the people who don't get an electrician in to fix the badly broken GPO (complete with copper showing) because 'it still works'.

(all from personal experience)

I mean - does your saw have a Saw Stop doodad to stop you chopping a finger off, or a power feed to prevent kickback injuries - or was that a little too much to pay to prevent such accidents and you did a price/safety tradeoff? But surely those features would be part of doing it properly, no?

No, but suggesting it is would be part of clutching at straws to justify your argument. It's certainly not illegal to operate a table saw without a power feed or a saw stop. Doing your own wiring is.

Yes, this does go so far as to include "undoing the screws a bit" - that's just as illegal as taking the whole point off the wall or undoing the terminal screws

Can you point to the section of the Electricity (Consumer Safety) Act (the relevant act in NSW) where it makes undoing the screws fastening a power point to the wall illegal? Even if it was, it does not strengthen your argument one iota. Me being wrong about that does not make you right about suggesting a home owner put a 15A point on a 10A circuit.

In the case of replacing a standard 10 amp GPO with a 15 amp one, you are replacing a GPO that can have one (or two or four or five) 10 amp socket outlets (potentially 50 amps concurrent load) with a single outlet that will be connected to a 15 amp load.

Your arguments are getting a little bit hard to follow but are you saying that the home owner should remove all of the existing 10A points on the circuit before fitting the 15A one? Or just that they should also unplug everything that's on that circuit?

If you read what I have written, I don't think you'll find I've said "Go and do this" - I've just provided options to help people clarify the issues so that they can make an informed choice.

Erm...

Of those three alternatives, I think that adding a 15 amp socket to a circuit that is protected by a 16 amp circuit breaker is the safer option

OK so you didn't say "go do this". You said "I think it's the safer option". Same thing? Yes I think so.

My suggestion is, as always, get an electrician to install a 15A point. And ignore people who try to give advice about whether or not YOUR wiring can handle a 15A welder on your 10A circuit without any knowledge of your installation or, as far as I can tell, qualifications to give such advice.

Can someone point out where this hypothetical situation fails here.

I have a single 10A GPO (in the kitchen for instance)
I (or my sparky) replace the single GPO with a double GPO (I assume the cabling does not need to be changed)
As a single GPO, the cabling would need to supply up to 10A
As a double GPO, the cabling would need to supply up to 20A
What's the big deal with running a 15A welder on the circuit?
Is a 15A GPO built any differently to a 10A outlet (aside from the obvious larger earth pin).
What is going to cause my house to burst into flames as some would sugest?

OK, as a professional Electrical Engineer working for 40 + years in the electricity supply industry, with a lot of my time over the past few years focused on rating of plant, my advice is :
DON'T RUN 15 AMP LOADS ON 10AMP CIRCUITS.

The reason ? The conductor for the 10 A circuit is rated at 10A, and this rating is determined by the maximum allowable temperature of the insulation on the wire carrying this current.

If you push 15 amps through this wire, the heat generated by this load is excessive to the designed heat withstand of this insulation, and may eventually melt the insulation, which in turn leads to live conductors (active and neutral) rubbing together with reduced insulation. When this happens it is usually accompanied by sparking ( ie that is the very principle on how arc welders work).
It is the sparking in a dusty environment in the ceiling that is one of the main causes of house fires. The other main cause is switchboard fires!

Switchboard fires are caused by the heating and cooling of the conductors connected to a fuse or circuit breaker. With this cycle of heating and cooling , especially when you get overheating due to excessive loads, the rear connections on the fuse or the c/b go through a cycle of expansion and contraction and eventually become loose, form a high resistance circuit, and start to heat. They can get red hot, insulation melts and peels away, arcing occurs and then a switchboard fire starts!

There is no way you would be covered by your house insurance for a fire of this nature if you deliberately overloaded the circuit. or any appliance ( like a GPO) on that circuit.

So, let me be clear in no uncertain terms:

DON'T RUN 15 AMP LOADS ON 10AMP CIRCUITS.

Can someone point out where this hypothetical situation fails here.

I think that the question itself indicates a lack of understanding of how circuits are planned for the expected load. Typically nothing you plug into a 10A point is going to draw anything like 10A. For example a fridge will draw about 3A. A microwave will draw about 3 or 4A. The electrician will estimate the demand and provide circuits and points accordingly. Typically your kitchen will have it's own dedicated circuit but bedrooms will share. The circuit breaker will typically be 16A or 20A, so you can draw up to that on each circuit before it will trip.

When a manufacturer puts a 15A plug on a welder, it is because they expect that the welder will draw more than 10A continuously. Depending on the welder, you might need a 20A or even a 30A breaker to stop it tripping at higher settings.

To work out the current draw, you divide the watts by the volts. For example a 6000 watt welder will draw 25A at full throttle.

Originally Posted by silentC

Typically nothing you plug into a 10A point is going to draw anything like 10A.

A fan heater can draw 2400watts. An oil column heater can draw 1800 to 2400 watts. A hair dryer can draw 1500 watts. Any combination of these could easily be plugged into the same double GPO.

This has nothing to do with load aggregation, rather, it's the entirely plausible worst-case scenario - after all, that's what the electrical system is designed to cope with in a safe manner.

If we push all the fear-mongering drivel aside, to me it's become patently clear that the effective function of the 15A plug is to avoid nuisance tripping, and that is the effective risk of plugging it into an outlet on a 10A circuit. I have not seen a technically-sound argument that it poses any increased risk to the internal wiring.

That said, I'm arguing about the actual risks - it certainly is *not* an encouragement to do so, becasue it is illegal to tamper with mains wiring unless you are licenced.