I just purchased a Lincoln Power Mig welder model 140C that Lincoln advertises as follows: “Wide 30-140 amp welding output range is the highest output in 120 volt input power welder class.”
In the operator's manual the requirement for the advertised maximum output states: "In order to utilize the maximum output capability of the machine, a branch circuit capable of 25 amps at 120 volts, 60 Hertz is required". The manual also states the recommended input fuse size is a 20 amp breaker and recommended input amps are 20.
The design of the Power Mig 140C type 5-15P power cord input does not provide for 25 amps at 120 volts because no 25 amp receptacle exists where a type 5-15P power cord will plug into it. However it will plug into a 20 amp receptacle. It's not possible to obtain a 25 amp breaker or a 25 amp (or larger amperage) receptacle that matches the 5-15P power cord. Beyond 20 amps a 30 amp circuit is the next highest circuit according to industry practice.
I certainly would appreciate any suggestions or insight in how to safely and legally obtain the advertised maximum output of my new welder without modifying the welder's NEMA Type 5-15P power cord.
You would definitely need a 30A/120v circuit for this. Even that is technically non-complaint since it would violate the individual load rating of 80%.
DO they give an advice on how to obtain this 25A/120v input? Such as changing the cord set?
There is NO WAY you will be able to safely and legally obtain a 25A input with typical 15 or 20A receptacles and circuits.
I gotta ask, why didn't you just get a 240v welder???
I haven't wired many circuits for 120 V welders, and when I did, I just used a 20 A receptacle on a 20 A circuit. Speedy, do you think that since we can up size the OCP to 200% of the supply conductor ampacity that this might also translate to the dedicated receptacle for the circuit? I mean, can we put a 20 A receptacle on a 25 A breaker if we are trying to be in accordance with 630.12? I want to give a tentative "yes", but I'm just not that familiar with it.
Why not? The Code makes no distinction on whether you are dealing with a residential situation or not.
Stubbie correctly pointed out that section 630.12 allows for upsizing of overcurrent protection to the sizes specified by the manufacturer.
We are held bound by the conditions of section 110.3 regarding manufacturer's instructions and listings. This does not change when other restrictions are placed on electrical installations. Upsizing of overcurrent protection where warranted is no exception. :whistling2:
My suggestion would be to use wire able to handle the 30 amp but install a breaker and plug for the 20 amps. Easer to upgrade latter. If you have a problem then the choice would be your. I would upgrade outlet and the power cord on the unit to the units input capability. However you may not run into a issue with the 20 amp plug unless you plan to use max output for a duration.
I certainly would appreciate any suggestions or insight in how to safely and legally obtain the advertised maximum output of my new welder without modifying the welder's NEMA Type 5-15P power cord.
Yours is rated 20 amps AC volts input for 90 amps at 19.5 volts DC in order to hold 20% duty cycle.. Your duty cycle is 20% at rated output which means you can weld continuously for 2 minutes out of a 10 minute period. In other words if you strike an arc and weld continuously for 2 minutes (unlikely) your welder must cool for the next 8 minutes. There is usually duty cycle protection with a thermal overload that will shut the welder off if you exceed duty cycle. It will reset when the welder cools enough. What all this means is if I turn the output voltage knob to around 19-20 volts dc I will pull 20 input amps. Some knobs will have amps so turning to 90 amps dc output will pull 20 amps ac input. Going above 90 amps output will draw more than 20 amps input and decrease your duty cycle. The welder is designed to weld from the minimum setting up to the rated settings all metal types and thickness as advertised. The need to provide a 25 amp circuit should not be required.
In order to supply the welder with a 25 amp branch circuit and keep your present supply cord you would need to utilize NEC 630.11(A) and NEC 630.12(A) and the exception in NEC 210.21 (B). In your case if you supply the welder with 12 awg you would simply increase the breaker to 25 amps much like we do with motors. Using 630.11 you could actually supply your welder with 14 awg as for a 20% duty cycle welder you can reduce the ampacity of the conductors by a factor of 45% of the nameplate input amps which is usually the rated current in your case 20 amps. Using 210.21.(B) allows you to keep your existing power cord even though your breaker is 25 amps. This is all because of duty cycle and being only 20% your welder will not allow the wire to get to hot enough to damage it before it shuts down.
However welding at over 90 amps rated output reduces your duty cycle below 20% by some margin. So at 140 amps max. (well above rated output) your duty cycle is likely to be somewhere around 10% or less. You also have an increase in input amperage somewhere between 20 and 25 amps. So you need a 25 amp breaker in order to weld at max. settings. This allows the inrush current when you strike your arc and the welder set at max.from tripping the breaker if it were to small. Plus more input amperage flows at settings above rated output current. Much like what happens with motors during start up. The internal circuit breaker of the welder will shut the welder down based on the duty cycle your welding at as it is a thermal preset. Low duty cycle means the welder gets hotter faster so the branch circuit conductors will not have time to get hot enough to be damaged before the welder shuts down if you exceed the duty cycle.
They probably bank on the fact that a 20 amp circuit breaker will never trip with a 25 amp load that is as intermittent as a welder. Would likely take hours of continuous 25 amp load to trip a 20 amp breaker.
Gentlemen, thank you all very much for your assistance and insight. It was all very good information. I found the answer to requiring a 20 amp circuit breaker while also requiring 25 amps available to that circuit in order to obtain the full output of the welder. As others have suggested, it's in the circuit breaker design and test criteria. The following is an excerpt from a circuit breaker manufacturer that explains the current carrying capabilities of most circuit breaker:
The CSA test program as well as our inhouse test program confirms compliance with the regulatory requirements by conducting the following tests:
Initial Trip time confirmation
The breaker is "over loaded" to a value of 135% of the current rating and the breaker must trip within one hour.
The breaker is then "overloaded to a value of 200% of the current rating and the breaker must trip in typically in less than two minuets.
Temperature test
The circuit breaker is overloaded to a current value of 6 times the rating ( but not less than 150 amp.) and switched 50 times.
The circuit breaker is then placed in a 40 deg. C. ambient temperature and forced to carry 100% of the current rating until the circuit breaker reaches thermal equilibrium. Temperatures are recorded and must be below the maximum temp. limits of the requirements.
Considering the welder's duty cycle it will operate at the 140 amps advertised by Lincoln so my previous assumptions were wrong.
Is this why my wife's 1875 watt blow dryer does not trip 15 amp circuit ? On the short list to change that to a dedicated 20 amp line...
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
DIY Home Improvement Forum
3.1M posts
319.6K members
Since 2003
A forum community dedicated to Do it yourself-ers and home improvement enthusiasts. Come join the discussion about tools, projects, builds, styles, scales, reviews, accessories, classifieds, and more! Helping You to Do It Yourself!