Thread: 15amp welders on 10amp circuits

Originally Posted by RustyArc

And my point was regarding the claim that a 10A circuit with a 15A device plugged into it was being run at 150% capacity when it isn't - it's a misnomer that leads people to think the wiring in the wall is going to burst into flame due to it being "overloaded".

A 10 amp GPO circuit is "designed" to supply appliances that draw no more than 10 amps from each GPO, up to the protective capacity of the breaker, correct? Well then as such you are exceeding the design capacity of the circuit by 150% by drawing 15 amps from a single GPO.

Originally Posted by RustyArc

As for whether the circuit impedance is not the same, I would argue that a single 15A socket with a dedicated run next to a 10A socket that has looped sockets back to the board, but with a similar length of cable will have similar impedance - I don't believe the looped connections at the intermediate GPOs adds significant impedance.

Your original quote was "so there's no difference in circuit impedance" and my point was that that was highly unlikely given the total number of joins in a 10 amp circuit compared to a 15 amp. I'm glad we finally agree.

Originally Posted by Vernonv

A 10 amp GPO circuit is "designed" to supply appliances that draw no more than 10 amps from each GPO, up to the protective capacity of the breaker, correct? Well then as such you are exceeding the design capacity of the circuit by 150% by drawing 15 amps from a single GPO.

I think 'nominal rating' is being confused with 'actual capacity'. The nominal rating is basically a marketing label, a label of convenience, while the actual or design capacity is based on engineering principals.

A single GPO might be rated at 10 amps, but you'll find that there is no difference in construction (terminal size, internal connections, socket connections) between a 10 and 15 amp point, as you can see from the thread here:

http://www.renovateforum.com/f195/th...15a-gpo-73298/

Looking at the detail in that thread, the thinnest part of copper in the switch mechanism for both a 10 and 15 amp GPO works out to be 3.9mm2,or roughly 60% more copper than the 2.5mm wire connecting it. So the switch mechanism - its actual designed capacity - should be right to at least 20 amps. (actually treating it as a 'non-metalic wiring enclosure in air' gives 2.5mm a rating of 22 amps and 4mm a rating of 30 amps, so you are looking at around 29 amps...or somewhere around 39 amps if you consider the mechanism as 'spaced conductors'.)

there is no difference in construction (terminal size, internal connections, socket connections) between a 10 and 15 amp point

The 15a thing is about the number of outlets and the size of the breaker. It's nothing to do with the 15a GPO being higher spec. It's about the design of the complete circuit. I don't know whether people think that those who devise these standards just do it for a laugh or what. Plugging a 15a appliance into a 10a socket simply exceeds the design of the circuit largely because it is possible to overload it if other appliances are also plugged in. The 15a circuit, with it's limited number of points, just prevents you from overloading it.

You can sit here all day and argue whether or not a 10a circuit can handle a 15a welder. It's all a bit academic unless you go out to the site and have a look at the guy's wiring (and know what you are looking at I might add). The wiring could be 50 years old for all you know. It always amuses me the ability of people to get into remote analysis of people's electrical installations without even a photo of the distribution board to go on.

This is exactly the reason we have wiring standards and the respective legislation to control people doing it. There are just too many who think that they know all they need to know about it because they can understand how to string a few power points together.

A little off topic but what should one expect to pay for a 15A installed?

I've been quoted $360 before and thought it was a bit pricy for running a wire through the roof to the junction box, I asked him why it was so expensive and he said it would take a few hours to do We are on a single level house and the junction box is around 15 metres away from the garage, a straight run through the roof.


Am I missing something or is ~ $360 standard.

Originally Posted by Master Splinter

ILooking at the detail in that thread, the thinnest part of copper in the switch mechanism for both a 10 and 15 amp GPO works out to be 3.9mm2,or roughly 60% more copper than the 2.5mm wire connecting it. So the switch mechanism - its actual designed capacity - should be right to at least 20 amps.

So is that the case for every gpo/switch ever made? If there isn't a definitive answer to this question, then it is (as Silent said) all a bit academic.

As a general comment (not directed at anyone in particular) - it's a fine and good to argue the theoretics of the standard, but when you try and use that as justification for suggesting that someone else do things that contravenes the standard, then I believe you have crossed the line. Encouraging people to do/modify their own wiring is one thing, but to encourage them to do it contrary to the standard is another.

Originally Posted by silentC

The 15a thing is about the number of outlets and the size of the breaker. It's nothing to do with the 15a GPO being higher spec.

Which is covered in this post:

woodworkforums.com/f160/15amp-welders-10amp-circuits-126819/index2.html#post1235262

Originally Posted by Ch4iS

We are on a single level house and the junction box is around 15 metres away from the garage, a straight run through the roof.

By junction box, do you mean the switchboard? It would have to be run to the switchboard and a new circuit added.

It probably would take a couple of hours - install new breaker, outlet, run cable, test, etc. Add parts and you are probably up for about that.

Originally Posted by Vernonv

By junction box, do you mean the switchboard? It would have to be run to the switchboard and a new circuit added.

It probably would take a couple of hours - install new breaker, outlet, run cable, test, etc. Add parts and you are probably up for about that.

Yea switchboard

Thanks.

Originally Posted by Vernonv

...... use that as justification for suggesting that someone else do things that contravenes the standard, then I believe you have crossed the line. Encouraging people to do/modify their own wiring is one thing, but to encourage them to do it contrary to the standard is another.

I am more concerned with people understanding what they are doing so they can make the safest possible decision.

This way, if they aren't going to do it the proper way (ie if you have someone saying "$360 for one single new power point - that's daylight robbery and I can tell you it ain't gunna happen"), I invite you to tell me what happens next.

Is it:

a) "Oh well, best I sell my brand new welder, then",
b) "I had better find a sparky who needs some welding done to see if I can get mate's rates",
c) "I'll just whack a 15 amp socket onto that point in the garage",
d) "I'll file the earth pin so it fits in a standard socket",
e) "I'll make up a 10 to 15 amp adaptor cord and plug it in when needed".

I suspect the chances of (a) happening are pretty much way off in statistical outlier land and would be closely related to the occurrence of porcine flight.

Out of the rest, (b) will be highly dependant on personal networks and timing, while (c), (d) and (e) seem to be the most likely outcomes.

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, as the only negative outcome is more frequent tripping of the breaker, but I would be happy to hear reasons why the other two possibilities may be better.

That's easy. Option c is illegal. Option d voids your warranty (imagine taking the welder back after it sh#ts itself and trying to explain the modification to the earth pin). Option e probably voids your warranty too, although that would be difficult for them to discover. However you are wilfully bypassing a system that was put in place by the manufacturer. So none of them should be given as responsible advice. If the person is too tight to pay $360 for a new point, they should consider a different hobby because $360 is SFA in the scheme of things.

Your community spirit in trying to educate people in the correct way to break the law or void their warranty is admirable, but I wonder where your personal liability would lie if someone follows your advice and has a problem. "Oh sorry mate, I'm not an electrician but I thought that would be OK"

Option 'C' would be criminally irisposable as the next person coming along would understandably asume it was a proper 15 amp circuit.

C and D are in my opinion irresponsible (and yes, possibly criminally irresponsible) as it will likely have a impact on other people.

$300-odd may be small in the scheme of things, but you are assuming that people make rational decisions. (any marketing professional will happily confirm that that's not the case).

When they've just paid $300 for a welder, plus another $60 for a helmet and gloves and rods, and maybe $150 for metal for that garden gate project, stumping up another $300+ and waiting an unspecified time till they can use their new toy seems unlikely to me. (especially if 'er indoors wants that gate up sharpish to stop the dogs tramping all over 'er loverly geraniums).

My rationale for thinking that a 15 amp socket on an existing circuit would be safer than the alternatives is as follows:

Aside from the number of connected GPOs, there is no difference between a 16 amp circuit which is feeding multiple 10 amp outlets or a single 15 amp outlet.

Both use the same circuit protection (16 amps), have the same insulation/isolation/resistance/impedance requirements, and use the same wire (2.5mm).

A 15 amp draw is happily within the 'yea, I can take this all day, even in 40 degree heat, and dude, I'm like totally surrounded by thermal insulation' capacity of the wire.

In use, the only difference an unsophisticated end user would notice is that when they are welding, and the kettle is put on, they pop the breaker fairly quickly and they've got to reset the clock on the microwave yet again. There is no 'detrimental' action to the circuit.

Of course, there's nothing stopping people using gaffer tape and fence wire to hold the breaker in the 'on' position, but these are probably the same sort of people who would solve the problem in the first place by inserting nails into the socket and wrapping bare wire from the lead around the nails, and insulating it with an old thong (hopefully of a footwear type).

For a person installing a 15 amp socket it means they actually have to take the GPO off the wall (you know, like half the population of Australia does illegally when it paints a room) and screw on the new GPO.

At the very least with this approach there is the opportunity to inspect the condition of the wiring and worry a little if it is oozing green goo or crumbling away when touched or is actually speaker wire with an earth that looks like it was salvaged from phone cord.

For the other possibilities (such as filing the earth pin/replacing the plug/adaptor cord) you create a high draw appliance that can now be plugged into any socket outlet in existence, from a standard 10 amp GPO connected to 50's rubber and paper insulation, a GPO mounted at ceiling height and meant for less than 200 watts draw, a $2.50 4-outlet power board made of 'geniwin frameproof prastik', or that tightly coiled 15 meter light-duty 7.5 amp extension cord.

I reiterate my statement in response #42.
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 another room.
Any alteration to the fixed wiring has to be done by a licensed trades man by law.
As for being able to plug it in a SPO (special perpouse outlet) meant for 200w, that should have a round earth but in any case be on a lighting circuit with 8 or 10 amp protection.
Sticking or tying up the circuit breaker will only hold up the toggle, the innards will still trip and break the circuit.

The correct answer was given by watson in answer #6