Normally, a 6 AWG copper or 4 AWG aluminum will do for this amp rating, but you can’t take voltage drop out of the equation, especially if it’s a sub panel that’s situated a bit far (100 feet or more) from the service panel. This is especially true when we don’t account for distance and possible voltage drop. It only determines its insulation and thickness, so it doesn’t matter whether it’s 110V or 240V when figuring out the correct wire size. What Size Wire Do I Need for 50 Amp at 110-240v? You can use the same formula for the other wire size recommendations made here if you want to confirm. keep voltage drop low) by upgrading to the next size! But if we use a 4-gauge copper wire instead, which has 0.253 ohms of resistance per 1,000 feet, then we arrive at:Īlready too close for comfort, huh? Hence, we play it safe (i.e.Maximum Allowable Resistance = 5% x 110 = 5.5 5.5 / 50A = 0.11 ohms We first need to get the maximum allowable resistance with regard to the panel’s voltage rating, amp rating, and voltage drop. Let’s take the 110V/120V sub panel as an example. If you’re wondering how these recommendations are made, you can get technical by calculating for resistance per 1,000 feet of each wire. The sizes for 100 ft will be 4 AWG copper and 3 AWG aluminum. On the off-chance that your panels are rated at 110V/120V, the right wire size for 50 amp sub panel should be bumped up to 2 AWG copper or 1/0 AWG aluminum for 200 ft.If the sub panel needs to power appliances and power tools 200 feet away from the service panel, it’s also advisable to use 4 AWG copper or 3 AWG aluminum.If the sub panel needs to be located at 150 feet distance from the main panel, then the most suitable 50 amp sub panel wire size would be 4 AWG copper or 3 AWG aluminum, but a 6 AWG copper wire size for 50 amps may still work.The golden rule is: once a significant voltage drop enters the picture, adjustments are necessary.īelow are the recommendations for 50 amp service wire sizes, with a focus on 50 amp 240 volt panels, as they are more common than 120V models. Theoretically, yes, you can still consider a 6 AWG copper or 4 AWG aluminum as the right size for 50 amp sub panel 100 feet away, as long as you confirm that your voltage drop doesn’t exceed 5%. Unless you’re installing the sub panel relatively close to the service panel (i.e just 50 feet away or at 75 feet), we’ll likely have to account for that drop. This requirement usually applies if your run exceeds 100 feet, given that this length results in a significant drop that will require you to increase the amp rating of the wire by 20%. Some electricians don’t even go past 2% voltage drop on the feeder and 3% on branch circuits because these percentages are considered beneficial for performance.Īnything over 5% may need bigger wires, which can reduce voltage drop. The NEC considers a 5% voltage drop as the maximum safety limit. However, these answers assume that there’s no voltage drop to consider. For aluminum, it should at least be 4 AWG. The Correct Wire Sizes for a 50A Sub PanelĪccording to the size chart recommendations from the 2002 edition of the NEC, the minimum wire for 50 amps should be 6 AWG for copper. What Wire Do I Use for a 50 Amp Sub Panel?.What Size Wire Do I Need for 50 Amp at 110-240v?.Calculating With Voltage Drop Considered.The Correct Wire Sizes for a 50A Sub Panel.

Nec wire size chart