Choosing the Right Engine-Driven Welding Machine

No matter the task at hand, it’s always important to have the right tool for the job. The same principle applies to engine-driven welding machines. However, with so much equipment available on the market, the process of choosing the proper engine-driven welding machine for your application can be overwhelming. Without the appropriate knowledge, it’s easy to choose the incorrect machine for a given application. It could be undersized and unable to meet the needs of the job, or it could be too large, which means you probably overspent. These judgment errors are made every day when buying or renting engine-driven welding equipment, requiring time, effort and money to correct.

You can avoid these pitfalls when buying or renting your next engine-driven welding machine by keeping five considerations in mind, as follows:

1. Fuel type

2. Welding output/duty cycle

3. Auxiliary power output

4. Engine manufacturer

5. Additional functionality


The first issue to consider is fuel type. The three primary fuel options are gasoline, diesel and liquefied petroleum gas (LPG).


Gasoline-powered, engine-driven welding machines are generally smaller in size and have more limited output capabilities. The typical gas welding unit will produce 300A or less of welding output. These are generally available at a lower up-front cost than a diesel machine, but they use more fuel and are prohibited on some jobsites due to the low flashpoint of gasoline. Further, the higher RPM gas engines require more frequent service.


Diesel welding machines are typically in the 300A class and above. They have a higher up-front cost than gas engines, but they are jobsite workhorses with more welding and auxiliary output than their gas counterparts. Diesel engines are also up to 35% more fuel-efficient and typically have a longer life than gas engines. In addition, some jobsites require diesel engines for safety reasons.


LPG engines are similar to gasoline engines, but they burn clean fuel. The LPG engine-driven welding machine is an ideal choice for environments where gasoline and diesel emissions are not acceptable

Welding output/duty cycle

After determining the best fuel option, it’s important to choose a welding machine/generator appropriately sized to your application. The most important thing to determine is how much output you need to run your welding process. Too often, customers ask for a 400A unit without knowing what that means or what they need. Consider what’s listed below when determining your needed output.

Shielded metal arc welding (SMAW)

When SMAW with electrodes up to 5/32, a 200A machine is usually sufficient. Larger electrodes require higher amperage, and a higher amperage will require a larger machine.

Gas tungsten arc welding (GTAW)

Like SMAW, GTAW is a constant current process. Most GTAW applications do not require more than 200 to 300A.

Flux-cored wire

When welding outdoors, wind tends to blow shielding gas away from the weld, so a flux-cored wire is needed to shield the weld pool. The wires used in this process require a constant voltage power source that’s typically 300A or larger. It’s important to consult your welding procedures to find out how much current you’ll need prior to choosing a welding machine.

Arc gouging

Figure 1: The Dual Maverick™ 200/200X engine-driven welding machine/generator is shown working on site in Cleveland, Ohio.

Arc gouging is a process that melts metal and blows it away, removing it from the base material. This process requires a great deal of energy and puts heavy stress on smaller machines. If you plan to arc gouge, a larger machine is recommended to remove material faster. For a 1/4 in carbon, the recommended output is 300A, while the recommendation for a 3/8 in carbon is 450A.

Single- or dual-output offerings

While most machines include one set of output studs, some offer two, like the Dual Maverick™ 200/200X from Lincoln Electric (Figure 1). A machine with multiple sets of output studs can be beneficial on crowded jobsites. One less machine means more fuel savings, reduced emissions and less noise.

Once you understand your process, consider the welding output, duty cycle and horsepower of a machine to ensure that it’s appropriate for your application.

Table 1: A breakdown of amperage class and IEC duty cycle rating is featured.

The first thing to understand is the real output of the machine. This is determined by the duty cycle. The industrial standard for welding machine duty cycles is the International Electrotechnical Commission (IEC) rating. The IEC rating uses a formula to calculate the amount of time you can run a welding machine at a specific amperage and voltage (Table 1).

In the first part of this story about choosing the proper engine-driven welding machine for your application, two points — fuel type and welding output/duty cycle — were reviewed. Here’s the second part of that story, where common pitfalls as well as the final three points — auxiliary power output, engine manufacturer and additional functionality — are provided.

Common pitfall #1: Comparing welding machines based solely on their model names

Some manufacturers sidestep the International Electrotechnical Commission (IEC) formula and give a name to their equipment based on an unrealistic amperage. This can steer customers into making misguided decisions, which will negatively affect their ability to perform the job. When shopping for a welding machine, what really matters is the true welding output and horsepower. Make sure to look beyond the product name and compare the specifications of competing machines that can be found in product literature or owner’s manuals.

It’s best to compare the IEC rating of each machine. Sometimes the current ratings of two machines will match, but the voltage or duty cycles will differ. Higher voltages, duty cycles and horsepower mean more output.

Lincoln Electric helps to eliminate this confusion by naming its Vantage® machines according to the IEC amperage class and horsepower. This gives the customers a clearer sense of what they are getting. Further, the company’s Vantage® engine-driven welding machine includes a nameplate that lists the duty cycle of the machine.

Auxiliary output

It’s also important to consider your auxiliary power needs. Engine-driven welding machines generate auxiliary (AC) power that can be used to run lights, pumps, power tools and other devices. As with welding output, it is important to review machine specifications closely to ensure a true comparison. The two ratings often used for auxiliary power are peak power and continuous power.

Common pitfall #2: Not comparing auxiliary power correctly

Peak, continuous, three phase, single phase — with so many different types and ways to rate the auxiliary (AC) output of your machine, it can get confusing. Here are a few things to remember that will help you get the amount of power you need.

Peak power vs. continuous power

The peak power will always be higher than continuous power, but can only be sustained for a short time (about 30 seconds or less). Peak power is needed for certain applications, such as starting pumps or other inductive loads, which can require a large in-rush current to get running. After that initial surge, it settles into the lower, continuous power rating. Continuous power is the power available at a 100% duty cycle.

Always be sure you are comparing peak ratings to peak ratings and continuous ratings to continuous ratings.

Single-phase vs. three-phase capabilities

Single- and three-phase auxiliary power are fundamentally different due to the design of the AC circuit. As a result, these two types of output cannot be directly compared. More importantly, jobsite tools may require one over the other. For example, most hand-held tools are single-phase, while many pumps, welding machines and plasma cutting devices require three-phase power. Furthermore, the available three-phase power will be higher than the available single-phase power.

Once again, be certain to compare available three phase with three phase and single phase with single phase.

Simultaneous welding and auxiliary power

Just like the weld output ratings, the auxiliary power ratings are the maximum output the machine can give you. These machines are designed to provide both auxiliary and weld output at the same time, but there is some give and take (Table 2).

Table 2: Example of auxiliary and weld output with various amps and watts.

As you can see, when you increase the weld output, the available auxiliary power decreases and vice versa. It is important to understand the needs of your jobsite (Figure 2) and application before you buy or rent.

Finally, depending on the machine’s available auxiliary output, it is possible to run a second operator by plugging in an inverter-style welding machine to provide two arcs simultaneously. For example, a diesel-driven Vantage® 549X can power a Flextec® 350X PowerConnect inverter welding machine.


Engine manufacturer

Figure 2: Pictured is the Hudson Yards construction site.

There are multiple engines available in the same amperage class. This is another important consideration in the buying process. Engine service networks can vary by location, so for maintenance reasons, you’ll want to consider an engine manufacturer that has a presence in your area. Also, you can streamline your maintenance operations by having the same engine manufacturer throughout your fleet for welding machines, lifts, tow motors and so forth.

Additional functionality

While all machines offer welding and auxiliary output, some machines offer additional functionality to maximize their versatility on the job site. Lincoln Electric offers engine-driven welding machines with integrated air compressors, hydraulic pumps and battery jump-start terminals. This can save space on your truck or job site, by combining multiple functions into one piece of equipment. Another benefit is you will not have to run cranes or tools off your truck engine, saving fuel and reducing wear and tear on the truck engine. It is especially useful in areas where vehicle engine idling is restricted.


With so many engine-driven welding machines available on the market, it is easy to get overwhelmed. Remember to keep the process simple by focusing on the five primary considerations outlined — fuel type, welding output/duty cycle, auxiliary power output, the engine manufacturer and additional functionality. Do not be confused by product names that can sometimes be intentionally misleading. All the information you need can be found on the product specification sheet or owner’s manual. Just look over the documentation and buy what you need.



Choosing the right engine-driven welding machine: Part 1 | Presented by AWS | 

Choosing the right engine-driven welding machine: Part 2 | Presented by AWS |

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