![]() This states that the voltage potential across the conductor is equal to Voltage drop is calculated using the most universal of all electrical laws: Ohm's Law. Source: NFPA 70, National Electrical Code, Chapter 9, Table 8 How to Calculate Voltage Drop Note: The results of this calculator are based on conductor temperatures of 75☌. Units for wire size are AWG or kcmil.ĭistance - Enter the one-way length of the wires in the circuit in feet. Wire Size - Choose the size wire in the circuit. To calculate ground wire size, use the Ground Wire Size Calculator. For three-phase circuits, four wires are required. Single-phase circuits, three wires are required. This is typically single-phase or three-phase. Phases - Select the number of phases in the circuit. Common conductors are copper and aluminum. To multiply the nameplate FLA by 1.25 for wire sizing.Ĭonductor - Choose the material used as a conductor in the wire. While three-phase voltages are typically 208V, 230V or 480V.Īmperes - Enter the maximum current in amps that will flow through the circuit. Single-phase voltages are usually 115V or 120V, It’s already a given that we need to adjust to 100A, so that shall be our base ampacity value when calculating.Voltage - Enter the voltage at the source of the circuit. 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.įor that, I factored in the 80% rule and the 20% amp boost guideline mentioned above. Naturally, I have to prove the figures I listed in the tables above. How to Calculate the Correct Size for 80 Amps This kind of wire has high heat resistance (up to 90 degrees Celsius), handles wet and dry conditions well, is suitable for indoor use, and is highly cost-effective. The Kind of Wire That Best Suits 80A Breaker PanelsĬopper THHN wire is favored because of its numerous unique benefits. If you’re curious, standard wires are insulated for 600V. It only determines the type and thickness of the conductor’s insulation. The answer is no, voltage doesn’t affect wire size. 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. ![]() Wire Size Adjustments Based on Distance and Voltage Drop for 80 Amps If you do want to know how to calculate, then head on over to the “How to Calculate” section below. I’ve prepared this 80 amp wire size table for you, so you won’t have to do the manual calculations yourself. You have to account for them even if you’re sizing for a smaller 70 amp or a larger 100 amp breaker. ![]() These adjustments will mainly involve boosting the total ampacity by 20% for every 100 feet. 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. However, the NEC does make it clear that wires for continuous loads must be sized at 125% of the rated load to ensure safety.īreakers’ size needs to match the wire they’re protecting, so they end up carrying only 80% of their rated current – hence, the “rule” above.Īnother big factor is voltage drops. Regarding the 80% rule, it technically doesn’t exist. Why did I use 75☌? Because wire size is typically rated at that temperature. If you have a copy of the National Electric Code, then turn to the page with the 310.16 table to confirm these recommendations. Likewise, 1 AWG is the suitable aluminum wire size for 80 amps. How to Get the Correct Wire Size for 80 Amps Every TimeĪssuming 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.
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