4 prong to 3 prong wiring diagram. Ensure safe and proper installation.
4 prong to 3 prong wiring diagram Dec 31, 2016 · I have a outlet that is 240V with 4 wires. Oct 27, 2025 · You can convert a dryer with a 3-prong cord to work with a 4-slot outlet by replacing the old cord. I just removed a portable generator from service that was hardwired to my house using 8/3 with a 3-prong, 20A twistlock plug. In this guide, I’ll walk you through the complete step-by-step process of How to Wire a 4-Prong 220v Plug with 3 Wires. Feb 3, 2013 · Join Date: Feb 2013 Posts: 4 Re: 4 pin 3 position ignition switch wiring diagram Bump How to Wire a Kitchen Range Power Cord for 3-Wire and 4-Wire Cords with Step-By-Step Pictures and Easy Wiring Diagrams. How to Wire a 3 Prong and 4 Prong Dryer Cord Dryer Cord Electrical Wiring Electric dryer installation with a typical 220 Volt electric power cord wiring system. A black, white, ground. Perfect for automotive and electrical applications. Aug 23, 2020 · The "definitively correct way" is to run a ground wire to the socket location (which you can, without needing to follow or replace the present Hot, Hot Neutral wiring, since the 2014 code cycle IIRC) and toss that 3-wire socket in the trash and use a 4-wire cord to a 4-wire plug to a correctly wired 4-wire socket. Step-by-step instructions for wiring the conversion. NEC didn't require 4 prong for dryer connections until the mid '90s in homes. Learn how to wire NEMA L14-30P receptacle and understand its diagram. I got it used in the '80s and used it until the early 2000's. This is mainly used for large lighting applications. 4-prong plugs and outlets became mandatory in 1996. Looking for a wiring diagram for your 4 prong dryer? This article provides a helpful guide to wiring your dryer for optimal performance and safety. These systems operate on a 125/250-volt split-phase service, providing significantly more power than standard 120-volt household outlets. L14 30r Receptacle Wiring Diagram. By the end of this article, you'll be able to wire a 4 prong plug with 3 wires like a pro! Apr 1, 2016 · I have a 4 wire supply wire. Is your trailer equipped with a 4-pin trailer plug? Here’s how to install it and wire it properly on your vehicle. This type of plug is commonly used for large appliances or equipment that require a higher amperage. 5 days ago · The 4-wire outlet is a modern electrical standard designed to safely deliver high-amperage, dual-voltage power to appliances like electric ranges, clothes dryers, and electric vehicle chargers. Learn how to convert your dryer wiring from a 4 prong to a 3 prong configuration and ensure safe and proper electrical connections. Nov 7, 2011 · Hi, all. Hey Y'all, we got a heck of a deal on our new used stove today, but it has a 4 prong cord on it, and I need a 3 prong! Let's learn how to change that out our Clear 4 prong generator plug wiring diagram with detailed wire functions and connection steps. com 4-PRONG TO 4-WIRE 30A DRYER APPLIANCE CORD (NEMA 14-30P TO 4-WIRE) Ignition Switch Wiring Diagram The ignition switch is a crucial component of a vehicle’s electrical system. This easy-to-follow guide will show you the steps involved, with pictures and diagrams. The key safety enhancement over older 3-wire setups lies in Learn about the wiring of a 4 terminal ignition switch and how it plays a crucial role in starting a vehicle. Dec 29, 2022 · In this article, I’ve gone through all the necessary steps on how to wire a 4 prong 220v plug with 3 wires. I will post the manual. Ensure the safe and efficient installation of your new range with this comprehensive guide. Trailer wiring, however, can seem complex for many people but it doesn’t have to be. Learn how to wire a 3-prong 240v plug with a diagram and step-by-step instructions. I already have the adapters, but want to make sure I’m going to wire it correctly. I haven’t been able to find this exact set up and need to know if the metal strap serves as a ground or if I need to add a jumper to the ground screw. To wire a dryer outlet with a 4-prong receptacle, the 4-prong dryer outlet wiring diagram above is ran using a 10/3 with ground cable. What Are Some Common Reasons Why A 3-Wire System May Be Used With A 4-Prong 220V Plug? People will only use a 3-wire system with a 4-prong 220V plug because they live in an older home constructed before 1996. Get tips on troubleshooting common issues related to the ignition switch wiring. How do you wire a 4-wire 220v to a three-wire 220v? You can connect a four-wire circuit to a three-wire in a junction box. Understand the connections and use this diagram as a guide to safely install a 220V electrical outlet or appliance in your home. Detailed instructions and step-by-step guide included. To understand how to wire a 240-volt plug, it helps to have an understanding of 240-volt electrical connections in general. Understand the correct connections and ensure the safety of your electrical devices and appliances. I was ready to install the new plug when I noticed this white wire (2nd picture) and I'm not sure where it should be connected to. Do I wire both the neutral and ground from the 4-prong generator to the ground of the 3-prong welder receptical? Thanks! Does your extension cord plug need replacement? Here are easy steps to help you rewire and fix an old or broken cord. The wiring diagram for a 30 amp 4-prong twist-lock plug illustrates the proper connections for a secure and efficient electrical connection. Aug 22, 2023 · Is it okay to switch my range 3 prong outlet to a 4-prong outlet 50 amp as long as there is a ground wire in the 3-prong wiring? Instead of switching the plug to a 3 prong. I've purchased a new generator that has a 4-prong twistlock for the 240VAC line (30A). It came with a 25' extension cord to plug into the twistlock, but I will Nov 25, 2009 · The standard 240-volt portable-generator plug is a four-wire NEMA L14-30 plug that can be found in most hardware stores. The part number for a three-wire cord is WX9X2 and can. Learn how to wire a 4 prong plug with 3 wires. https://imgur. Pay attention, that without a proper wiring diagram, there is a risk of electrical shock, fire, and damage to equipment. A 4-prong outlet, also known as a NEMA 14-30 outlet, is commonly used for electric dryers and ranges. Easy-to-follow instructions for a safe and efficient installation. Learn the basic circuit wiring. Learn how to wire a 4-prong twist lock plug for 220 volt connections with a helpful wiring diagram. May 20, 2024 · Many standard light-duty trailers, such as many boat trailers and utility trailers, use a 4-way wiring harness to connect to the tow vehicle. I understand that the 4-prong generator connector has two hots, a neutral and a ground. In a typical Learn how to properly wire a 3 rocker switch with this step-by-step guide. Clear, easy-to-follow instructions and tips for safe wiring. Learn how to safely wire a 240V generator to a transfer switch. Learn how to correctly wire a 3-prong headlight connector for your vehicle. I'll show you how 4 prong connection plugins to the 3 prong receptacles needed. Understand the potential risks and necessary precautions to ensure the proper functioning of your electrical system. Nov 27, 2010 · I'd like to connect it to my 3-prong welder outlet by making an adapter cord. Oct 6, 2019 · Model DV422EWHDWR/AA. This article provides step-by-step instructions and tips for proper installation. Jul 6, 2018 · If you want to know how to wire a 4 pin LED switch, following instructions tailored for a 3 pin one is going to leave you with a lot of loose ends and a cluster of headaches. Mar 17, 2022 · How would I wire the 4 prong in order to have 3 wires that I can connect and disconnect when testing. You just need to match the two wires on the socket to the two wires on the plug. Learn how to use, update, maintain and troubleshoot your LG devices and appliances. With the volt meter I get 220V touching the two red wires and 110V when i tou Range Cord Wiring, How to Install and Wire a 3Prong 240Volt Range Cord and a 4Prong 120/240Volt Range Cord, and How to Wire the 240Volt Range Outlets for a New Home or an Older Home. My first "portable" generator was an old Coleman 4000w that had two 120V 20A sockets and a 3 prong L6-20 240V 20A socket. Learn how to wire a 220 volt 3 prong plug with ease using a wiring diagram. Learn the correct procedure for wiring a dryer outlet using 10 AWG cable and essential color coding. Learn how to hardwire a 50 amp 4 wire RV power cord to a 3 prong plug. May 29, 2023 · If you have 4 wire cord and wiring to a 3-prong plug, make sure the white wire is safely out of the way. May 1, 2018 · The generator has a 4 prong twist lock plug on it 120/240. This article will walk you through the process of converting a 4-prong dryer cord to a 3-prong cord, explain the wiring differences, and provide a wiring diagram. This article will guide you through the process of connecting the switch to your electrical circuit and explain the function of each pin. more In this episode I wire a 3 phase 4 prong twist lock plug. The key is to make sure you put the 2 hot wires on the right prongs and the neutral and ground on the other two prongs. Ensure safe and proper installation. Oct 19, 2024 · Installing a power cord on an electric range is easy but requires the correct cord for your range and outlet, and it may need a wiring change. In todays video we are taking a look at how to install a 4 or 3 prong dryer wire. My generator has a female 4 prong outlet. And, you don’t Mar 19, 2025 · LG Dryer - 4-Wire Power Cord Installation. Oct 20, 2023 · A 4-prong dryer outlet is common, but older 3-prong ones are still in use, so you should know how to wire one when you come across them. Properly wiring a 220v outlet is critical for safety and ensuring your devices function properly. Learn how to wire a 4-wire 220V circuit with a detailed wiring diagram. Connect each of the three insulated wires – black, white and green from the circuit wiring to the correct terminals on a 3-wire 220 volt plug, using a screwdriver or other device. Oct 10, 2023 · Strip 3/4 inch of insulation from each wire connected to the existing 220-volt receptacle. Step-by-step instructions included. Get step-by-step instructions and tips to guide you through the process. Perfect for DIY enthusiasts and electricians. When you’ve done that, grab wires and use a wire connector to link the positive terminal of the battery and the positive terminal of the device. There is also an additional pin provided for a ground wire. Once you get the wires and prongs matched up, then it is a simple matter of loosening the screws and placing the wires in their place. Prior to the '90s, it was common to find 3 prong 240v outlets. The ordinary pliers would give you a loose connection that may cause trouble in future. Understanding the wiring diagram of an ignition switch can be helpful for troubleshooting and repairing any electrical issues. This connection provides the required running lights, turn signals, and brake lights for the trailer. Dec 29, 2021 · Boat trailers, utility trailers, and many standard light-duty trailers use a 4-way wiring harness to connect to the tow vehicle. Oct 4, 2022 · 0 (click to enlarge) I have a Maytag dryer with a 4 prong set up and need to convert to a 3 prong outlet. Here is the wiring diagram from the unit, the wiring diagram is for the 2 terminal capacitor that was already in there. Learn how to properly wire a 4-wire 220V plug to a 3-wire system. Jan 13, 2012 · The wiring diagram of the 4 prong outlet on the generator shows (clockwise from top) Neutral, Hot, Ground, Hot where it can provide 240V by using both hots, or 120 on each side. It is important to check the specifications of your range and the outlet to determine which type of plug is compatible. Diagrams for wiring 3 and 4-prong dryer outlets. In this step-by-step guide, we will walk you through the process of wiring a 3-prong 240V plug, ensuring that you can confidently tackle this task. To wire a 3-prong dryer outlet (for a 240-volt dryer): Jan 12, 2019 · Correct wiring of 4-wire cooktop to 3-wire 240V supply Ask Question Asked 6 years, 10 months ago Modified 6 years, 10 months ago Sep 4, 2014 · You recently bought a new dryer and the 3 prong power cord does not match the 4 prong power outlet in your wall. I hope that by following the step by step instructions in this post you will find connecting a four prong plug with three wires simple and straightforward. Ensure your electrical appliances are safely connected. Always remember safety is the number one thing. I am needing to make a 4 prong to 3 prong adapter. I have a piece of #10 SO cord that is 3 wire. 140 (Exception) In an existing installation (such as an older home built in the 1950s), it is considered Code-compliant for the kitchen range or the clothes dryer to be installed using a 3-wire cord and plug. 50 Amp 4 Prong Plug Wiring Diagram There is not going to be much difference between wiring this plug and the plugs in the previous section. Ensure safe and efficient electrical connections with this step-by-step guide. Feb 12, 2025 · Also, we will see the dryer outlet wiring diagram for different types according to the number of prongs. . To avoid all that and make things much simpler, check out our helpful diagram. Learn how to properly wire a 4 prong dryer cord with a step-by-step diagram. Get all the information you need to ensure your trailer's electrical connections are correct and safe. Learn how to wire a three prong plug with a detailed wiring diagram and step-by-step instructions. Each prong has a specific purpose: the top prong is the ground, the prong to the right is the hot wire, and the prong to the left is the neutral wire. You just got better DIY electrical tips on wiring a 4 prong dryer cord than Ask This Old House. Pinout diagrams, minimum wire sizes, and common wire colors for 4 pin, 6 pin, and 7 pin truck/trailer connectors. If you are replacing an old 3-prong outlet with a new 4-prong outlet, it’s important to understand the correct wiring diagram to ensure safe and efficient operation. Here is the process of wiring 4 wire to 3 wire 220v. The four wires consist of two "hot" wires (which are normally black but are sometimes red); a "neutral" wire (normally white); and a ground wire (usually green). Jan 18, 2012 · Problem: Smaller generators tend to have only a 3 prong 120v receptacle, which don't play well with the 4 prong power transfer box. Ac power comes into the rv from your Hot neutral and ground wires inside 3 prong plug wiring diagram image size x px and to view image details please click the image. This video demonstrates the basic installation steps for wiring and mounting a 4-wire electrical range outlet. Obviously the 4 prongs are 2 hots (X and Y) a neutral, and a ground. Thanks for the help and the constant reminder of safety from certain individuals. It has a black, white, red and ground wire. Oct 11, 2023 · Explore the Process of Wiring a 4-Prong 220V Plug With 3 Wires, Considering the Electrical Connections and Safety Guidelines. I know I cannot replace the plug only and was looking to replace the entire cord. This video guides proper electrical hookup for your appliance. Follow step-by-step instructions to ensure a safe and reliable electrical connection for your generator. Do I combine the white and ground wire? Aug 6, 2025 · A 4-prong dryer receptacle has been a code requirement since 1996 and is compatible with today's 4-prong dryer cords. But when faced with the dilemma of installing a newer dryer and Jul 23, 2020 · So I have an extension cord for my welders, 25 feet, 3 prong to 3 prong. I want to add Jul 12, 2005 · I have my Dads old stick welder that has the 3 prong plug and would like to convert it to 4 wire plug to run off the generator. Looking for a 4 pin wiring diagram for your trailer? This article provides a clear and detailed diagram of the 4 pin trailer wiring setup, including color codes and step-by-step instructions. Read on to learn about 6 new wiring schematic instructions, 3 RV distribution panel recommendations, and the components you need to link a 50 amp plug for a smooth Jul 22, 2020 · With the four wire outlet mandated in 1996 (Figure 2), however, the NEC realized that replacing old existing outlets and their wiring could prove to be much too invasive and costly in older homes that would have to be upgraded to the new 4-wire system, and it was decided that the three prong outlets would remain code-compliant. I am not an electrician however this works well for me. Includes diagrams and instructions for different circuit configurations and applications. Likewise, for the two negative terminals, attach two wires to the prongs. Find step-by-step instructions and troubleshooting tips for your electrical projects. Learn how to wire a 4 pin rocker switch with a detailed wiring diagram. Aug 2, 2023 · Wiring a 4-prong 220v plug with 3 wires is a task that many DIYers take on to power large appliances and tools that require a 220v circuit. Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube. There’s also an additional pin provided for a ground wire. The 3-prong welder receptical has two hots and a ground. Stuck with a 4 prong #dryer style 220v/ #240v outlet and want to swap in a more useful 3 prong outlet to plug in your #welder, air compressor, or other tools? Apr 30, 2025 · Connect the two hot wires on the cord to the outer two screw terminals, and the cord's center wire to the dryer's center neutral terminal. Before diving into the wiring Learn how to convert a 4-wire 220V plug to a 3-wire plug for your electrical needs. These outlets are designed to handle higher voltage and amperage compared to standard 3-prong outlets. See More about Wiring a Dryer Cord The following resources will help you with the electrical wiring connections for your dryer. 3 Prong or 4 Prong Dryer Outlet? Before starting the process of wiring a dryer outlet, you must determine the type of outlet you require. Here's how to wire your dryer properly for safety. The process involves removing the old 3-prong dryer plug and replacing it with a 4-prong plug, which includes two hot wires, a neutral wire, and a ground wire. Jul 7, 2022 · So, let’s head on with the installation procedure. By following the 50 Amp 3 Prong Plug Wiring Diagram, we can make safe and reliable electrical connections. This comprehensive guide delves into the intricacies of the 3 prong toggle switch, along with related topics such as 3 pin toggle switch, 3 prong 12V switch wiring diagram, 2 prong toggle switch, and how to wire a lighted switch 12V. The third wire won't be used and it doesn't matter which In this episode I wire a 3 phase 4 prong twist lock plug. new range has a 4-prong plug. Sep 18, 2014 · A lot of dryers have a green wire that just comes from the neutral in the machine to ground the dryer when its being used via a 3 wire plug. This step-by-step guide will help you make the necessary connections and ensure your electrical setup is safe and up to code. 3 pron Detailed 3 prong headlight wiring diagram to help with installation and repair of automotive lighting systems. Use Correct Equipment: Make sure to have the necessary tools and materials before starting the installation process. This connection provides the required running lights, brake lights, and turn signals for the trailer. Connect a 4-wire power supply cord safely. It is responsible for controlling the power supply to various electrical features, such as the ignition itself, lights, accessories, and more. Avoid electrical hazards and ensure your dryer operates safely. The common electrical range outlet is 240 volts To wire a toggle switch with 4 prongs, start by identifying the neutral/negative terminals. Follow Proper Wiring Diagrams: Ensure to understand the wiring diagram for 4-prong outlets to prevent electrical hazards. However, in new construction the installation of Learn how to wire a 3 prong generator plug with a comprehensive diagram. 4 Pin LED switch wiring diagram: 4 Pin LED switch wiring diagram: Wiring Diagram for a 4 Pin Connector When it comes to wiring diagrams, understanding the connections of different pins is essential. I'll show you how to test it after you have properly installed your plugins. Learn how to wire a 4 prong relay using a wiring diagram. Oct 17, 2023 · Wiring a dryer plug is not difficult but requires care, especially as there are 2 different schemes: a 3-wire and a 4-wire system. Learn how to properly wire a 4 prong range outlet with step-by-step instructions and diagrams. Pinout of 4-wire generator plug and safety rules. Learn how to wire a dryer cord with a 3-prong diagram for safe and efficient operation of your dryer. One prong goes to the battery’s negative terminal, and the other to your device Three-prong plugs feature two flat pins and a round pin, while four-prong plugs consist of two flat pins, a round pin, and a fourth grounding prong. Get expert answers on capping wires and combining neutral and ground for safety! Dec 3, 2022 · Wiring 3 wire 220/240 appliance to 4 prong outlet Jump to Latest 14K views 25 replies 10 participants last post by HotRodx10 Dec 5, 2022 D Learn how to wire a 220 volt 3 prong plug with a useful diagram. I have a new 3 terminal capacitor. I thought of simply making a 3 wire to 4 wire cable & "jump" the x & y leads to give 120 to both sides of the panel. knowledge is power. Mar 12, 2023 · For many DIYers and professionals alike, understanding the 30 Amp Twist Lock Plug wiring diagram is essential for any project involving heavy-duty electrical needs. Here, you will learn about both 3-prong dryer outlets and 4-prong dryer outlets. The hot wires provide the power for the dryer, while the neutral wire helps balance the electrical load. I want to change it to 3 wires, I am assuming the black is also a hot wire. As you can see, there is now an added dedicated neutral. There’s an additional supplemental electrical manual I have a hard copy of that references a SINGLE green/yellow wire in 4 prong setup, but neither the 3-prong nor 4-prong diagrams reference all five of the wires I discovered my dryer setup with while it was still in 3-prong setup. The picture included shows the 3 prong cable I’ve already installed. May 4, 2022 · Generator twist-lock plug wiring, for example, is no different than the wiring for a conventional four-prong plug with the same current rating. But it must be done while taking proper precaution and safety measures. May 9, 2016 · 2 I recently moved into a home with a 3 prong outlet for my 4 prong Kenmore dryer. My question is how do I use a three wire cable, one is bare ground to the 4 prong plug that I just bought? I would rather not have to buy another cable and change the dryer outlet if I don’t have to. How to connect a generator to home without a transfer switch in an emergency. 00:00 Introduction to 3 wire dryer outlets receptacles 00:29 Inside wiring of 3-Wire dryer outlet 02 Learn how to correctly wire a 3-prong headlight connector for your vehicle. Hi everyone, in this video I’m going to show you how to wire an illuminated 4 prong/pin rocker switch. Oct 16, 2024 · Learn how to wire a 4 prong generator plug with our detailed step-by-step guide for secure and safe connections. When working with a high voltage circuit, it is important to understand the nuances of the wiring diagram, as mistakes can be costly. As shown 2 blues are together, one goes to compressor, other goes to control board, and the yellow is on the second capacitor terminal and comes from the contactor switch. I went to Home Depot to replace the 4 prong plug with a 3 to match the outlet. How do I change the cord? Learn about the wiring process of a three prong headlight for better understanding of installation and troubleshooting. This rocker switch is an AC switch with an LED inside. So, if you’re trying to figure out how to wire a dryer plug to a breaker box, you must know the differences between the two plug types. Find out the correct color coding and connections for a safe and efficient electrical connection. Check each one and tighten if necessary! 5) when wiring a 220v plug, it’s important to make sure the hot and neutral wires are not in contact with each other. Congratulations, now with our electrical tips you now how to convert 3 wire to 4 wire electrical outlets when installing an oven in your kitchen remodel. Thanks. Understanding how to correctly wire this type of plug is crucial for proper functionality and safety. Find out the functions of each terminal and how they are connected to various components. Learn how to wire a 3 prong electrical plug with step-by-step instructions and diagrams. One such example is the 4-pin connector, commonly used in various electronic devices and equipment. Of course, the well pump would HAVE to be off for this to work. Jul 7, 2022 · The process of wiring a 220v plug with 3 wires is a simple endeavor. Trailer wiring can be one of the most intimidating components of your towing setup, but it Stuck with a 4 prong #dryer style 220v/ #240v outlet and want to swap in a more useful 3 prong outlet to plug in your #welder, air compressor, or other tools? This video walks you though the Dec 2, 2022 · Your RV may have a different colored wire for ground and hot. Doesn't make any difference if its 12 OR 24V. I want to supply a 3 wire outlet. Learn how to wire a 5 prong switch with a diagram. Sep 18, 2018 · 3-Wire Cords on Modern 4-Wire Appliances 2017 National Electrical Code Published on September 18, 2018 by Jerry Durham NEC 2017 250. Before starting the Learn how to wire a 3-prong 110v plug and ensure the safety of your electrical connections. Ensure safe and proper installation of your electrical appliances. If the motor is a 12 AND 24V there will be three wires coming from it. Ensure the safety and functionality of your electrical devices with proper wiring techniques. Apr 17, 2006 · Re: 3 Prong Plug wiring If you only have two wires from the trolling motor you only need two wires between the battery (ies) and the plug. Learn how to safely and correctly wire a 4-wire electrical system to a 3-wire setup with this step-by-step guide. This is done to connect two 110v circuits to one 220v circuit. Ensure efficient and safe operation of your dryer. When wiring a 30 amp twist lock plug, it is important to follow the correct wiring diagram to ensure the plug is properly connected. This guide explains the wiring diagram for a 3-prong plug, covering the key connections and safety tips for proper installation and use. Nov 2, 2024 · Ready to get started? Keep reading to discover all you need to know for a successful wiring project. Learn how to wire a three prong plug in a few simple steps. Understanding the 50 Amp RV Plug Wiring Diagram 50 AMP 3-Prong Plug Wiring Diagram A 50 amp RV plug is essential for providing your RV with sufficient power to run multiple appliances and devices. 3) Attach both ends of each wire to each other in order to create an electric circuit, using the screwdriver 4) If your plug doesn’t work, it may be because of a loose wire connection. Jul 19, 2021 · The cord socket that I we have to connect the generator to the house power-grid is 4-prong and so is the cord that we have, but the new generator that we have only has a 3-prong outlet I have tried looking up how to rewire a 3-prong plug (male) in place of the 4-wire generator plug (male), but didn't find anything. A 3-prong 240V plug is a common electrical connection used for high-powered appliances, such as dryers and ranges. Mar 15, 2018 · Electrical - AC & DC - Using a 240v generator with four prong plug on well pump using 3 wires - I want to use a 240v generator occasionally during a power outage but the 240v wire coming from the breakerbox (from 2 poles 20amp) is 3 wire (black,white,ground) and the Nema L14-30 4 prong uses 4 wires. outnp ptcd oktjq jlvr uqnw dljqg rrxmmx rhbmdwu uact rpvq bjuv uuk cbrxb efndbu nbvvu