right size circuit breaker
Fuse

The wiring for any device needs to accommodate its current requirements, and as you know welders draw huge amounts of current and need substantial wiring.

Thus, you will need to understand the right size of the circuit breaker for the welder as well as the amount of amperage needed in order to operate a MIG welder.

What size breaker do I need for a 220v welder?

Circuit breaker sizes are usually determined by the amount of current that the devices need. For instance, a device which needs 27 amps would need 30 amps circuit breaker.

Meanwhile, the wire gauge used in order to wire a circuit also needs to accommodate the specific current that is allowed by the circuit breaker. A circuit with 20 amps circuit breaker will need a 12-gauge wire at a minimum.

Thus, for 220v welders you will need to go with 30 – 40 amp breaker, meanwhile, for smaller 115v a 20 – 30 amp breaker should be enough. For 3 phase, you will need up to 50 amp breaker depending on its voltage.  

For the type of outlets you need, a smaller 115v welder allows a normal home 3 prong outlet. Running on a 220v or 30 amp welder plug, you will need a 4 prong or a 3 prong heavy duty outlet.

Conductor Sizes and Welder Circuits

Various conductor sizes with insulation also support various amounts of current. For instance, an 8-gauge wire can handle at least 40 amps of current, while 50 amps will need a 6-gauge wire.

In addition, it is always best to size the wiring and welder circuits based on the input current requirements of your welder. 

For instance, a 240 volt, 40 – 50 input amp welder will need a 50 amp circuit breaker plus 6-gauge wiring. Meanwhile, welders operating at 30 – 40 input amps will need an 8-gauge wire and at least a 40-amp breaker. Smaller welders operating below 30 amps can go with a 30-amp circuit breaker and 10-gauge wire.

How Many Amps Do You need For An MIG Welder?

This depends on your MIG welder and what you are planning to weld with it. Here are a few basic questions to determine how many amps you need for a MIG welder.

  1. Material thickness to weld

If you are planning to weld on thicker materials of around ½ inches, then you will need a 220v welder since it can help you burn hotter and penetrate the material.

Meanwhile, if you are only going to weld ¼ inches thick materials or less, then a small 110v welder should be enough.

  • Welder Application

If you are planning to run production for a small business or run the welder around the farm, then you can go with bigger 220v welders.

But, if you want to use the welder for more efficient, high-end production, then a 3 phase welder that should give you anywhere 300 – 600 amps of power or more should be your bet, which is unlikely.

Take note that you’ll need a 3 phase power in order to run a 3 phase welder. Most homes can only run a 200 amp welder. So, you will need converted wiring in order to run this kind of welder.

However, if you only plan to use the welder on small projects around your small shop or home, then a 110v welder requiring 30 amps and producing up to 140 should do just fine.

  • Power

The last thing that you will need to think about is power. If you are welding in your garage with access to 115 volts, then this may limit you in what you can get.

For smaller shops or farms, you will have the option of 220v welders that allows you to get a higher amperage machine. Lastly, if you are running a small to medium-size business, then you will need to have access to 3 phase power in order to run bigger welders.

Another Important Consideration: Duty Cycle

The duty cycle is referred to as the amount of time that a welder can operate at a specific amp. In general, the duty cycle is shown as a percentage.

If a welder has 30 percent at 90 amps duty cycle, this means that it can weld continuously for at least 3 minutes and requires a 7-minute rest before you can start welding again.

If the welder has a duty cycle of 20 percent at 90 amps, then you can weld continuously for 2 minutes then let it cool for 8 minutes.

In simpler terms:

Every 10 percent of duty cycle = 1 minute of welding time

Now, what’s the problem with the duty cycle?

It is when you need to weld for longer periods of time in a row. For most people, this might not be a problem, but for those working with complicated materials on huge projects, then the long duty cycle comes in to play.

Another problem with the duty cycle is that the more amps you use, the lower is the duty cycle. For instance, a smaller 110-volt welder running on 140 amps should only be able to do a 30 percent duty cycle at 90 amps.

The good news is, there are welders that can operate at a 100 percent duty cycle. But, these are the bigger welders that typically run on 3 phase power. For the average welder, this is not an option.

Welders that run at higher amps work better for material welding since you can cut back on the amps and take a higher duty cycle.

For instance, a welder with a 40 percent duty cycle at 250 amps can get a higher duty cycle if you cut the amps at 200. Then the duty cycle is probably at 100%, so you do not need to run at the highest amps at all times.

The Advantages Of Higher Amperage Welders

High amperage welders offer you more advantages. Some of them include:

  • WELD THICKER MATERIALS: With a higher amperage welder, you get to weld thicker materials without any problems.
  • DEEPER PENETRATION: In terms of welding, penetration is always the name of the game. The deeper the weld can penetrate, the more likely it will hold.
  • CLEANER AND CONSISTENT WELDS: Welders with higher amperage offer a consistent and clean weld look, giving a professional-looking finish on your projects.
  • MORE OPTIONS: In the end, a welder with higher amperage just provides you with more options when it comes to power settings.

Conclusion

To sum it up, for a small 110-volt welder I would use at least 30 amps circuit breaker. For bigger 220 volt welders I would use a breaker that is at least 40 amps, possibly even bigger if possible. The bigger fuse for your workshop wiring is even more important if you are planning to run multiple tools at the same time. For example, weld, grind and maybe use an air compressor as well. To do all the task simultaneously, you will need more current, thus a bigger circuit breaker.