I know it's been covered before but I couldn't find the info I needed in the old posts. My Miller Mig is of the 3 prong type but the Dryer outlet I need to plug into at my brothers house is a 4 prong type. Can an adapter cord be made to go from 3 to 4 prong? I picked up a replacement dryer cord at Lowes with the proper 4 prong outlet. I also picked up the 3 prong female end that matches my welder. I was planning to put the two together for an adapter cord. But, now I am not sure if this can safely be done. What wire goes to what and what about the extra wire? if anyone has done this before please help. Thanks for any help in advance rustfarmer
On a single phase 4-wire outlet, the four wires are: Hot usually black Hot usually red (180 degrees out of phase of the other hot lead) Neutral usually white Ground usually green Between the red and ground or neutral, you get 110V AC Between the black and ground or neutral, you get 110V AC Between the black and the red, you get 220V AC On the dryer, they need the neutral wire so they can get 110V for the timer and certain other things, while the heater elements probably need the 220V. On a welder, you get the 220V between the two hot leads, and don't need 110V for anything, so the neutral lead isn't needed. So for the welder all you need to connect is the two hot leads and the ground. In socket assemblies, the ground screw is often plated green. Make sure you cap off the unused neutral wire somehow so that it doesn't make contact with any of the other wires. So if you want to make an adapter cord, hook the red to red (hot), black to black (another hot out of phase with the first hot) and the green to green (ground), and you should be all set. The current rating of the socket and cord needs to be the same rating as the outlet and breaker. It's probably not considered a legal setup, but as long as you're doing this strictly for your own use and you disconnect it from the wall when you're done, you should be okay. Edit: I thought I should add that the ground wire is only for safety in the event that a hot lead shorts out to the case of the equipment to keep you from getting shocked. It is not legal to run current through a ground wire. That is why the 4-wire cord has a separate "neutral" wire which is used for carrying current when something needs 110V. Back at the panel the neutral lead is connected to the ground bus bar. If you wire up an adapter, you want to cap off the unused white "neutral" wire, and make sure the green wire gets connected to ground. The green wire is the one that could save your life if something inside your welder shorts out to the case of the welder.
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