![]() Voltage DropĪccording to the National Electrical Code (NEC) guidelines mentioned in 210.19(A) (1), the recommended voltage drop shouldn’t exceed 3%. The things to consider include the following: 1. ![]() Factors to Consider for Wire Size SelectionĪside from the elements already mentioned, think about other important factors that can affect your wire selection for a 400-amp panel. Meanwhile, if it’s -140☏ underground, you will need a 1250 kcm aluminum wires instead. ![]() How many phases? (singel, parallel or three?)įor instance, if you want a suitable 400 amp 3 phase wire size for your house, opt for 600 kcm copper wires or 1000 kcm alumnium wires.Should you use copper or aluminum wire?.Determine the correct cable to use by asking yourself the following questions: Requirements to Choose the Right Wire Size for 400-Amp ServiceĪpart from the wire type, reflect upon other requirements in choosing the correct wire for a 400-amp electrical panel. However, it usually has thicker insulation than THHN models. An XHHW cable generally has a single conductor. Cross-Linked Polyethylene High-Heat and Water-Resistant Wire (XHHW)Ī type of wire size for commercial and industrial use.It usually has non-metallic sheathing used for branch wiring. With THWN, you can take advantage of high water resistance, allowing the wire to resist temperatures of up to 167 degrees Fahrenheit (75 degrees Celsius) when wet.Ĭommonly known by its trade name Romex, a residential service will generally use this type of wire for a 400-amp electrical panel. The THWN wire has similar traits as a THHN cable, except for the focused resistance. Thermoplastic High-Water-Resistance Nylon-Coated (THWN).As its name implies, its high heat and oil resistance can make it a suitable choice in a diagram with various appliances and types of machinery. Thermoplastic High-Heat-Resistant Nylon-Coated (THHN)Ī single conductor wire is commonly used in different buildings.The four kinds of cable sizes for 400 amps to watch out for are the following: Each classification has its unique pros and cons. Wire types typically fall under four categories. Doing so helps reduce the risks of issues for the panel, the circuit, and the connected devices. Understanding the different wire types available for a 400a service is vital. Factors to Consider for Wire Size Selection.Requirements to Choose the Right Wire Size for 400-Amp Service Last edited by Matt Marsh 10-02-2014 at 3:37 PM. If you run a #6 bare copper GEC, you can run it exposed on the surface unless it is subject to severe physical damage (250.64(B). ![]() Although the minimum size grounding electrode conductor is typically #8 copper for a 100 amp service (it's actually determined by feeder size, not amperage), the NEC requires that conductors smaller than #6 be physically protected (usually conduit). It is almost always easier and more cost effective to satisfy the NEC requirement by supplementing one ground rod with an additional one (250.53(a)(2). The measurement must be performed with a dedicated ground resistance meter, something that very few contractors have. The only way that you can get by with a single one, is if you can prove by measurement that the ground resistance is 25 ohms or less. If you are using rod type electrodes, you really need to drive two of them, at a minimum of 6' apart. The only exception is if the separate building is fed with just a single branch circuit (2014 NEC 250.32a). Jason, A separate building always requires a grounding electrode system in addition to the equipment grounding conductor that you mention.
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