Circuit Breaker- How Many Amp's?

G'day guy's
Long time reader and first time poster.

So, I've decided to buy myself a MIG (Not the one with jet propulsion).
After reading through all the informative posts on welding, I've just got my tax return and thought I'd make a start.

The first thing I needed to do was to get a 15amp power point installed. I've got an electrician coming tomorrow for a quote. My question is, How many amps should the circuit breaker be? Can I use a 40 amp breaker? Should I?

I've decided to get myself a Lincoln 180C as my first welder.
A friend of mine has a Unimig 160, and he throws the circuit breaker on first turn on from cold. I don't know haw many amps his breaker is. Might be 20amps I think.

Any advice or opinions would be great, Thanks.

Hi DirtPig, welcome to the forums.
The circuit breaker is rated to protect the cable. Not what is plugged into it. Your electrician will install a suitable breaker for the cable installed.
If you are worried about tripping the breaker on startup ask your electrician about a 'D' curve breaker. They are designed to withstand higher inrush currents and will prevent nuisance trips on startup.
Be sure to post some pics of the first welded project :2tsup:

Thanks NCA,

A "D-Curve" breaker, you say.
Never heard of one of those. I'll let the Sparky know and add it to the install.
I'll also post the total cost of the install when finished to give the forum an idea of how much it is to install a 15Amp socket nowaday's.

The short answer is that in most circumstances a 15 amp powerpoint has to be a dedicated run to a single 15 amp breaker.

My strong recomendation is to fit a 20 amp powerpoint, that will of course be connected to a 20 amp breaker.

That is the biggest available standard power point and your 15 and 10 amp plugs will still fit it

The difference in cost should be minimal.

As far as neucance tripping....I run standard Hager MCB/RCD units on all mu circuits both in the shed and in the house and have no problem with nusance tripping......if the breaker is tripping there is a good reason.

I run all my heavy stuff of this outlet and never a problem.....saw benches, welders and so forth.

cheers

If you're running a new circuit, the sparky will match the breaker to the cable being run, and what it's run through. For a 15A socket a sparky would typically run 2.5mm2 cable protected with a 16A breaker if the cable is run under insulation (leading it to heat up more) or 20A otherwise. For a device with a 15A plug either scenario will be fine, even with standard C curve breakers.

If you want to have multiple 15A sockets on the new circuit, then that becomes an aggregate demand calculation and gets a little more complicated. But from the sound of it, it should be a very straightforward install.

We just finished cabling our new shed

We used a 6mm feed to a sub board then 4mm for all power points

IMO the minimal extra investment to run the thicker cable ensures you will never have any problems and power should be more stable with high usage appliances such as welders

Former Forum lurker with first post here also.

I had my new man cave wired up last year with a dedicated 15A circuit for my MIG and TIG welders. The breaker is 16A. Not that I had anything to do with it - I just told the sparky what I was going to do with the circuit and he wired it up (and takes liability for it).

I've had no problems with trips at all on that circuit. Works just fine with a 240A MIG and 200A TIG.

Cheers

Matt, You say that you haven't tripped the breaker using a 240Amp MIG.
Wouldn't a 240Amp MIG trip a 16amp breaker at full noise?

This raises another question for me.

How do you actually read the specs of a welder?
In so far as, you normally have a range and duty cycle at certain amps. How does this relate to the input amperage?

I don't know if these are silly questions, but being a complete novice, I'm trying to wrap my head around all the jargon. I've ordered the lincoln 180c and that has an input amperage of 10.7 Amps; so no worries there. But if at a later stage I want to upgrade the welder, How high an Amperage machine can one go on a 15AMP PLUG?

To work out the amount of amps an appliance draws find the compliance plate which should have all of the electrical info. It will normally have the amount of watts the appliance will use. The maths is watts divide volts ( which will be 240) equals amps. i.e. a 2400 watt appliance will draw 10 amps of power. A 15amp outlet is rated to just that - 15amps. If you go over that what should happen is you will overload the 16amp circuit breaker and it will trip. 2.5mm wire can hold up to around 22amps give or take a bit depending on climate and length of cable. The new inverter welders will run smoothly on normal 10amp outlets without too much worry. It all depends what else is using the same circuit for power. Hope that helps a bit.

Serioulsy, with most of the modern solid state welders, you won't find too many welders that will go above 15 amps in single phase.

As far as how far you can push a 15 amp circuit.

2.5mm2 cable will easily carry 20 amps continuous and there is no way you will burn cables with a legally fitted breaker, there is heaps of safety factor in the way the regs are written.

standard circuit breakers must hold at twice their rated value for a short time..how long depends on the specification, but a full minute is not unreasonable.

Both the ability of the circuit breaker to hold excess current and the ability of the cable to carry the excess current are necessary to allow for peak inrush for starting lots of things.
for example my saw bench that draws arround 20 amps free running draws well over 50 amps on start up...this is normal for motors.

The old choke style welders also pull high inrush currents on arc strike and elecrode sticking situations.

The electronic welders are far more efficient and better behaved that the old choke bassed units.

All this worrying about tripping breakers is unnecessary......if you are using reasonably modern breakers ( like less than 20 years old) and modern electronic welders, you should not be having any issues with tripping breakers on a dedicated circuit, as long as you are using a welder as specified according to the regs.
for example

properly fitted 15 amp circuit with 16 amp breaker
welder that has a legally fitted 15 amp plug and is specified as drawing less than 15 amps.

the problems we have with tripping breakers is mostly where things are not to specification...like when you fit a 10 amp plug to a 15 amp machine or file down the earth pin.....then use it on a normal 10 amp outlet, where there may be other loads on the circuit.

Run to specification and to regulation and you should never have a problem tripping breakers.

As far as how far you can go with a 15 amp circuit...a 250 amp solid state machine is about the limit.

I think you will find almost all electronic machines over 250 amps will be either 3 phase or 415volt single phase..which is a whole different game.

with the older choke style machines about all you could hope for was arround 140 amps.

any way..unless you are welding aluminium, 180 amps will do plenty big steel mate.

cheers

I stand by my recomendation to go with a 20 amp socket though for other reasons