These types of insulation are designed for use in high-temperature and wet environments. Additionally, use THHN or XHHW insulation.While copper wire is more expensive, it is also more durable and has a higher ampacity than aluminum wire. It is recommended to use copper wire over aluminum wire.The National Electrical Code (NEC) provides guidelines for wire sizes and ampacities for copper and aluminum conductors. The wire size is typically determined by the ampacity (current-carrying capacity) and the voltage drop.In the case of a basic 120V panel and load circuits, change the value from 240V to 120V and find the wire size in AWG. The calculation is based on a 240V main panel or subpanel installation at a mean temperature of 75☌ (167☏).Net total of general lighting and small appliances = 3 kVA + 7.35 kVA = 10.35 kVA Suppose the total required load for a load center, main panel (or sub-panel), is 24kVA designed for general lighting, and we need to identify the wire size for that service while considering the demand factor (diversity factor).Īccording to NEC Table 220.42 and (220.45), the first 3 kVA is rated at 100%, while the remaining load can be rated at a demand factor of 35%, in the case of general lighting load. 10kW x 80% = 8kW and do the calculation based on it. In that case, if the rating of required load is 10kW, we will use 80% of the load i.e. water heater, ranges etc.), the demand for 1 unit in Column B of Table 220.55 is 80% of nameplate. NEC 220.14 permits 220.55 and Table 220.55 to be used for calculating branch circuit loads for ranges. Similarly, electric iron, stove, hair dryer, light bulbs, washing machine, and TV, etc., are not running at the same time. We all know that almost all loads can’t be operated at once for example, only the air conditioner operates in the summer (while the heater is OFF), and vice versa in the winter. Wire Size for 100A Subpanel with Demand Factor Related Post: What is the Right Wire Size for a 4.8kW, 240V Range: #10 or #12?.For aluminum wires, a #3/0 AWG wire is typically used for a 100-amp subpanel having a distance of 100ft.Īs the finalized size of the wire is based on calculated values and general rules of thumb, it’s always recommended to consult with a licensed electrician for electrical installations.This wire size can handle up to 120 amps (80% of 130A), which is more than the 100A breaker rating. For copper wires, a #0 AWG wire with a 150 amp median capacity is most appropriate.The wire size should be selected such that it can carry 80% of the rated current of the breaker, which in this case is 100 amps.It means, an the wire having ampacity of 150A is sufficient to deliver 100A to the the load circuit located 100 ft away.įor a 100-amp subpanel that is 80-100ft away from the main panel, you would need to consider both the current capacity and the voltage drop due to the distance. Required Wire Size: #0AWG (1/0 AWG) Cupper (#3/0 for Aluminum)īased on the above calculation and AWG chart and tables based on NEC, the right size wire for 100 amp circuit at a distance of 100 feet from the main panel to subpanel is 1/0 AWG (AKA #0 AWG). To address this, we will perform a more detailed calculation based on NEC and related tables to determine the correct wire size for a 100 Amp circuit over a distance of 100 feet. However, this may not be a suitable approach when considering distance, as it can lead to high voltage drops. In the US, a 25kVA, 7200V/240V distribution transformer provides electric power at 100 amps as follows:īased on this calculation, the ideal wire size for a 100 Amp breaker is #1 AWG for copper and #1/0 AWG for aluminum, according to the AWG Size chart and NEC Table 310-15B (formerly 310-16) Article 310.60 (given below). How to Wire a Subpanel? Main Lug Installation for 120V/240V.
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