What Size Breaker For Welder? The Right Size

Most often people fail to realize the importance of using a suitable sized circuit breaker. But it is the most important thing to keep your electrical appliances safe and protected. And when it comes to welding machines, it’s even more crucial because it draws a huge amount of current. Thus, it needs the right-sized breaker with substantial wiring.

So, what size breaker for welder?

It should not exceed the maximum amperage output of the machine. The safest spot for the breaker is 125% of the current flowing through the electrical appliance.

However, if you are planning to purchase a welding machine that runs on a 220V outlet you may ask, what size breaker do I need for a 220V welder? It depends on the input current requirement. In this article, I have tried to explain how to determine the size of the breaker with easy equations. Lastly, you will get a quick chart for commonly available welders.

What Is A Circuit Breaker?

Circuit breaker is an automatically operated electrical switch designed to disrupt the flow of the current when there is an overload or a short circuit. Unlike a fuse, which needs to be replaced after breaking the circuit only one time, a breaker resumes its operation again automatically after resetting. It keeps the electrical and electronics appliances safe from excess current flow or short circuits.

Why Correct Sized Circuit Breaker Needed?

Using the right size circuit breaker is a must. Otherwise, if you use an oversized circuit breaker, it might heat up the wire or the connected device. Furthermore, short circuits might occur and in the worst case, it might start a fire and burn the circuitry.

Again, using an undersized breaker can break and reset the circuit again and again. This is what you get for using a wrong-sized breaker in the welding machine.

So, for preventing mishaps and maintaining a smooth operation correct-sized breaker is required. But how to know the size needed for your welder? It’s okay if you don’t know. I have got you covered. Read the next section.

What Determines the Size of a Breaker?

Before determining what size of a circuit breaker is needed for the welding appliance, keep in mind its size must not exceed the maximum amperage rating. So, check your welder’s maximum amperage output first.

When the circuit current is less than the circuit breaker’s rating, normal operation will be continued without breaking the connection with the main supply. In case of fault occurrences like short-circuit or excessive current flow, it will trip and protect the electrical appliances from damage or burn.

To give you an example, a 50-amp breaker will break the connection with the main supply at 50 amp, doesn’t matter it is a continuous load or a non-continuous one. So, if a 100 amp circuit breaker is used for a 50 amp circuit, it will not be able to break the circuitry when the current flow exceeds over 50 amp. As a result, it defeats the purpose of setting the breaker in the first place. So, we must use the correct size of the circuit breaker according to the circuit’s current flow. For the safety of the electrical appliances, the breaker’s size must not exceed 125% of the device’s current flow.

Let’s say, for a 20 amp circuit the circuit breaker’s size will be,

20 × 1.25 = 25 amp

If you don’t know the amperage rating of the device you can determine this from the device’s power and voltage level. To solve this, I am using the equation,

I =    ; Where I indicates current in ampere, P indicates power in Watts and V is for voltage.

For example, if it’s a 2000Watt device, and runs at 120V, then the required size of the breaker will be,

I =   = 16.66 amp

Now, multiply it by 1.2 or 1.25 if that size is not available for the circuit breaker.

16.66 × 1.2 = 20 amp

This is how you determine the circuit breaker size according to the device’s power usage.

What Size Breaker for Welder

Now, coming to what size circuit breaker you need for your welding machine. If it’s rated for 120V, it can only be used for 120V. It can’t be used on 240V circuitry. However, if it’s 240V it can be used for both 240V and 120V. So, for the welders which have dual input voltage having 120V/240V capability, 240V rated breaker should be used with that.

A 240V welder having 40-50A input will need a 50A circuit breaker and 6 gauge wiring. While the welding machine running at 30-40A requires a 40A breaker and 8 gauge wiring with that. If your welder runs below 30A, then it will need a 30A circuit breaker with 10 gauge wiring. 120V welder needs 20A breaker with 12 gauge wiring.

What size breaker do I need for a 220V welder, you ask? 30 to 40A one depending on the machine’s amperage rating with 8 gauge wire will run smoothly without any issue. For the 115V welder, a 20-30V rated breaker will do.

To give you a clear and concise idea I have prepared a chart. Check it below for the welder’s circuit breaker size and how much wiring will be needed with that:

Input Voltage Input Amperage Rating Circuit Breaker Size (Ampere) Wiring
115V 20-30A 12 gauge for 20A

10 gauge for 30A

120V 20A 10 gauge
220V 30-40A 10 gauge for 30A

8 gauge for 40A

240V 30-40A 40A 8 gauge
40-50A 50A 6 gauge

The Bottom Line

Circuit breaker keeps the electrical appliances safe by breaking the connection with the main supply when needed. To maintain a smooth operation for welding, it’s crucial to use the proper size. Otherwise, it will be of no use.

In the worst case, your device might get ruined by a short circuit or excessive current flow. So, better safe than sorry. Determine what size breaker for welder you do need actually. If you already using the correct size kudos to you. And if you aren’t using the right one, stop using the welding machine. Go and get yourself the perfect size one for a smooth and healthy operation.