Two Power Sources in One Machine

Every engine driven welder delivers two outputs: welding current and auxiliary AC
power. The auxiliary side runs grinders, drills, lighting, pumps and battery chargers—often while
welding. Managing both outputs correctly prevents overload, protects the machine and keeps the crew
productive.

Understanding Auxiliary Power Ratings

Auxiliary output is rated in kilowatts (kW) at a specified voltage (120/240 V). Two ratings
matter: continuous (what the machine can deliver indefinitely) and peak /
surge (short-duration for motor starts). A machine rated 10 kW continuous may deliver
12 kW peak for a few seconds—enough to start a compressor motor.

Sizing Auxiliary to Your Site Loads

  • Grinders (7 in): 1.5–2.5 kW each.
  • Mag drill: 1.0–1.8 kW.
  • LED flood lights: 0.1–0.3 kW per unit.
  • Submersible pump: 0.5–1.5 kW.
  • Air compressor (small): 2–3 kW.
  • Tool battery chargers: 0.2–0.5 kW each.

Add the loads you will run simultaneously and compare to the engine driven
welder’s continuous auxiliary rating. Leave 20% margin for surges and power factor.

Welding While Running Auxiliary Loads

Welding and auxiliary power share the engine’s total output. At full welding amperage, the
available auxiliary capacity drops. Check the machine’s combined-output derating curve—for
example, at 300 A weld output, a 10 kW machine may only deliver 5 kW auxiliary. Plan
heavy auxiliary use (compressor starts, pump operation) during welding pauses.

Load Management Tips

  • Prioritize critical loads: Run lights and safety equipment on dedicated circuits;
    switch off non-essential tools during heavy welding.
  • Stagger motor starts: Start compressors and pumps one at a time to avoid
    simultaneous surge demand.
  • Use GFCI on all 120 V outlets: Wet sites are shock hazards; GFCI protects
    the crew.
  • Distribute across phases: On 240/120 V split-phase machines, balance loads
    across both legs to avoid overloading one side.

When Auxiliary Is Not Enough

If site loads exceed the engine driven welder’s auxiliary rating, add a dedicated generator
rather than overloading the welder. Overloading causes voltage drops that destabilize the arc and
trip breakers—or worse, damage the alternator.

Conclusion

The auxiliary side of an engine driven welder is a real productivity multiplier,
but only when loads are sized and managed correctly. Calculate simultaneous demand, respect derating
during welding, and protect circuits with GFCI. Explore our engine driven welder
models with auxiliary output to match power to your site needs.

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