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What Size Wire for 80 Amp Breaker? – A Detailed Guide

Written by Edwin Jones / Fact checked by Andrew Wright

what size wire for 80 amp breaker

Acquiring the answer to the question, “What size wire for 80 amp breaker?” can understandably be confusing. After all, 80 amps aren’t really listed in the NEC wire size chart. There’s no better resource to get the answer from than that book.

Since that’s the case, we look at the next largest size in the 75°C column while applying the 80% NEC rule on conductor size. 80% of 100A is 80A, so we’ll use the wire size recommendation for 100 amps instead.

That means the correct wire size is at least 3 AWG copper or 1 AWG aluminum.

Read on for a detailed answer and other possible adjustments you need to make.

How to Get the Correct Wire Size for 80 Amps Every Time

wire-size-for-80-amp-breaker

Assuming your wiring run won’t reach 100 feet, to the point that it begins to cause voltage drops, then you can consider the correct 80 amp THHN wire size as 3 AWG copper. Likewise, 1 AWG is the suitable aluminum wire size for 80 amps.

If you have a copy of the National Electric Code, then turn to the page with the 310.16 table to confirm these recommendations. Why did I use 75°C? Because wire size is typically rated at that temperature.

Regarding the 80% rule, it technically doesn’t exist. However, the NEC does make it clear that wires for continuous loads must be sized at 125% of the rated load to ensure safety.

Breakers’ size needs to match the wire they’re protecting, so they end up carrying only 80% of their rated current – hence, the “rule” above.

Another big factor is voltage drops. If you’re wiring for 80 amp sub panel that’s quite far away from the main panel, and you’re certain that there will be more than a 3% voltage drop, that’s the time to start adjusting.

These adjustments will mainly involve boosting the total ampacity by 20% for every 100 feet.

You have to account for them even if you’re sizing for a smaller 70 amp or a larger 100 amp breaker.

I’ve prepared this 80 amp wire size table for you, so you won’t have to do the manual calculations yourself. If you do want to know how to calculate, then head on over to the “How to Calculate” section below.

Wire Size Adjustments Based on Distance and Voltage Drop for 80 Amps

80-amp-wire-size

Distance Correct Copper Wire Size
100 Feet 1 AWG
150 Feet 1 AWG
200 Feet 1/0 AWG
300 Feet 2/0 AWG

I’m going to make it clear here for those who are wondering whether they need to look at voltage when determining electric service wire size. The answer is no, voltage doesn’t affect wire size.

It only determines the type and thickness of the conductor’s insulation. If you’re curious, standard wires are insulated for 600V.

The Kind of Wire That Best Suits 80A Breaker Panels

Copper THHN wire is favored because of its numerous unique benefits. 80 amp breakers are no exception.

This kind of wire has high heat resistance (up to 90-degree Celsius), handles wet and dry conditions well, is suitable for indoor use, and is highly cost-effective.

How to Calculate the Correct Size for 80 Amps

Naturally, I have to prove the figures I listed in the tables above. You may be, perhaps, wondering why the 80 amp breaker wire size for both 100 feet and 150 feet runs are the same: 1 AWG copper.

For that, I factored in the 80% rule and the 20% amp boost guideline mentioned above. It’s already a given that we need to adjust to 100A, so that shall be our base ampacity value when calculating.

  • For distances at exactly 100 feet, we have the formula: 100A x 120% = 120A
  • For distances spanning 150 feet, the formula becomes: 100A x 130% = 130A

If we look at the NEC wire table again, we’ll see that 1 AWG is appropriate for exactly 130A.

It just so happens that the smaller size next to it (2 AWG) can handle 115A, so I had to upgrade the conductor size to 1 AWG to accommodate 120A.

The same goes for the longer distances. They’re fairly straightforward to calculate, since we’re using 100A as the adjusted wire size for 80 amp breaker.

  • 100A x 140% = 140A
  • 100A x 160% = 160A

Confirm the wire recommendations by referring to the Table 310.16 of the NEC.

FAQs

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What happens when you choose the wrong one?

Too small wires can get too hot, so don’t be surprised if the breaker will trip frequently or the wires will melt.

Overheating ruins wire insulation as well, leaving their internal, electrocuting parts dangerously exposed to people. Obviously, this also doesn’t bode well for home safety.

Does distance matter for 80 amps?

Yes, it will always matter because longer distances often mean higher voltage drops. We’re talking about a 3% to more than 5% drop that causes appliances to work poorly. Such setups are not without fire risks either.

Can 8 gauge wire handle 80 amps?

An 80 amp breaker box being served by 8 gauge wire is severely undersized. 8 AWG wire can only handle 50 amps at most, and we haven’t even accounted for the 80% NEC rule in that.

Conclusion

I hope I’ve dispelled all the lingering doubts you may have about what size wire for 80 amp breaker is best. As a recap, here are the points you need to remember:

  • Get a copy of Table 310.16 as a steady, credible reference.
  • Factor in the 80% rule on breaker ampacity to get the correct wire size.
  • Add 20% to the maximum rated ampacity for every 100 feet or more of the wire’s run.
  • Make sure the electrical cable size chart amps you’re looking at also takes into consideration all the necessary factors mentioned here.
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