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  1. #1
    Join Date
    Jan 2014
    Location
    Northern West Virginia
    Posts
    37

    Default Wiring a new home workshop

    I am not an electrician but I do have a little bit of experience in house wireing and a lot more experience wiring boats and automobiles. What I wanted to do here is just toss out some thoughts for guys who want to run dedicated circuits into their home shops safely.

    You know why the line to your shiny new welder has a fuse (circuit breaker) in it? It is not there to protect your welder or any other terminal device. Nope, that ain't it. The breaker is there for one purpose and one only. Its there to protect the wire - which in likelyhood is inside a wall where it can't be seen or monitored for heat build up.

    If your house is somewhat new it likely that you have a breaker panel (fuse box) that is rated at 200 amps. Right at its top it will have a main breaker of that capacity. The actual service to your home may very well be higher powered than that, ours for instance has 360 amp service going in. My point is that the entrance defines how much you have to work with in total.

    When you decide to wire an outlet for your home-shop welder it is important that you know how much power it will consume at its highest use and the build in over protection from the breaker all the way to the welder's plug. You can never be too safe when it comes to the potential for home fires.

    So, you start by determining what your maximum load will be and then you build to accommodate it. I'll give a real-life example in a moment. By build to accommodate I mean to size your breaker, wires, and outlet to the task at hand. The bigger the wire the more power it can carry safely. How big? Well, its a matter of amperes (amps). More amps demand heavier wire. Here are some simple guidelines:

    14 ga. wire is good for up to 15 amps
    12 ga. wire is good for up to 20 amps
    10 ga. wire is good for up to 30 amps
    6 ga. wire is required for up to 50 amps. (edited to change wire size)

    Now, a 'how I did it" for wiring the dedicated outlet for a small welder. The welder I bought last week (MM211) draws just under 30 amps at maximum load. It draws so close to 30 amps that a 30 amp circuit was out of the question, we built in our first level of protection by installing a 40 amp breaker, about 35% over the minimum need and not one single dime more expensive than a 30 amp breaker. We then wired it with 8 gauge wire, which for our 50-foot run from the breaker box to the outlet cost me about $25 more than the next size down. Cheap insurance that will last a lifetime. The outlet (NEMA 6-50 if I remember correctly) is already sized for its power requirement so it is what it is. Wiring of the circuit was straight forward except that the outlet is peculiar in that no neutral wire is used; just two hots and a ground. I won't go into "bonding" but somewhere back in my "Service Entry" there is a little green screw that connects the existing neutral wire to the ground plane (earth) and that allows it to work and also conform to the National Electric Code (NEC).

    What that means is that my welder, which draws 28.something amps is fed first by an outlet that is rated for 50 amps, which is fed by wires that are entirely capable of providing the 40 amps of power my 40-amp circuit breaker will allow to pass with no fear of fire.

    And that's the story, size up, don't take a chance, it too cheap to do it safely and its a lifetime investment in your own safety.

    And then there is the matter of extension cords. I would no more use a 14 or 12 ga. extension cord to power my welder than I would hit a honet's nest with a hammer. For one thing the heat that will build up in that wire is heat that is not available for welding - its just wasted. Heavy cords not only reduce wasted energy but they also prolong the life of the device they power, a somewhat expensive blue box in this case.

    And that's my story. Do not skimp when installing your power, it is false economy at best and can not only lead to home fires but also can eat into the life expectancy of your equipment. An extra $50 spend now can save you a lot more than headaches down the road.
    Last edited by 1_old_man; 02-01-2014 at 05:58 PM. Reason: Edited in response to member comments, my bad.

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