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  1. #1

    Default 110v Power on a Welding Table?

    I've got a welding table that I want to "electrify" so I have 110v power to serve my grinders, etc.

    Has anyone had any bad experience grounding the 110v supply to the table? I got to thinking that having a 110v ground wire connected to the table may "zap" my welder when it's ground wire is connected to the table.
    MTBob
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  2. #2
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    There can be a lot of issues here and it gets complicated. One of the best alternatives is to feed this table with 2 wire from a gfci outlet. This eliminates the possibility of using the electric ground as an alternate path for the work ground on the welding machine.

  3. #3
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    Some of this depends on other factors, is this a single bench in a shop, what type of construction, is there any possibility of this bench becoming energized from other circuits, is it interconnected with other benches and where does the welding machine sit? Most metal in a shop should be grounded to the electric service.
    Here is example of a potential problem. Say your machine is sitting on a metal cart, work ground laying on it or hooked to it and a grounded power supply 120V or even grounded tool laying on the table, you forget the work lead, strike an arc and the electric ground wire from the 120 becomes the work lead for the welding circuit.
    Mine are interconnected and in a steel building. I fed with 2 wire gfci but have a heavy ground lead connecting them and to the building, I did not use ground conductor in the supply circuit.
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  4. #4
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    (for purpose of this discussion) Any metal with the potential to become energized needs to be grounded and the grounding conductor must be in the same cable, pipe, wire or raceway as the power conductors. (the building frame is not to be used as a ground conductor) The exception to this rule is power supplied from a ground fault protected circuit.

  5. #5
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    For replacement of non-grounding-type receptacles with grounding-type receptacles and for branch-circuit extensions only in existing installations that do not have an equipment grounding conductor in the branch circuit, connections shall be permitted as indicated in 250.130(C). C) Nongrounding Receptacle Replacement or Branch Circuit Extensions. The equipment grounding conductor of a grounding-type receptacle or a branch-circuit extension shall be permitted to be connected to any of the following: (1) Any accessible point on the grounding electrode system as described in 250.50 (2) Any accessible point on the grounding electrode conductor (3) The equipment grounding terminal bar within the enclosure where the branch circuit for the receptacle or branch circuit originates (4) For grounded systems, the grounded service conductor within the service equipment enclosure (5) For ungrounded systems, the grounding terminal bar within the service equipment enclosure If you use the water pipe, the connection must be within 5 feet of where the pipe enters the building.
    You are permitted to replace a two-wire nongrounding type receptacle with a GFCI under the following in section 406.3 (3) Nongrounding-Type Receptacles. Where grounding means does not exist in the receptacle enclosure, the installation shall comply with (a), (b), or (c). (a) A nongrounding-type receptacle(s) shall be permitted to be replaced with another nongrounding-type receptacle(s). (b) A nongrounding-type receptacle(s) shall be permitted to be replaced with a ground-fault circuit interrupter-type of receptacle(s). These receptacles shall be marked "No Equipment Ground." An equipment grounding conductor shall not be connected from the ground-fault circuit-interrupter-type receptacle to any outlet supplied from the ground-fault circuit-interrupter receptacle. (c) A nongrounding-type receptacle(s) shall be permitted to be replaced with a grounding-type receptacle(s) where supplied through a ground-fault circuit interrupter. Grounding-type receptacles supplied through the ground-fault circuit interrupter shall be marked "GFCI Protected" and "No Equipment Ground." An equipment grounding conductor shall not be connected between the grounding-type receptacles. When you make this change be very, very careful that you get the hot "black" wire on the right side of the outlet.


    (B) With Circuit Conductors. By an equipment grounding conductor contained within the same raceway, cable, or otherwise run with the circuit conductors.
    NEC HANDBOOK COMMENTARY;
    One of the functions of an equipment grounding conductor is to provide a low-impedance ground-fault path between a ground fault and the electrical source. This path allows the overcurrent protective device to actuate, interrupting the current. To keep the impedance at a minimum, it is necessary to run the equipment grounding conductor within the same raceway or cable as the circuit conductor(s). This practice allows the magnetic field developed by the circuit conductor and the equipment grounding conductor to cancel, reducing their impedance.
    Magnetic flux strength is inversely proportional to the square of the distance between the two conductors. By placing an equipment grounding conductor away from the conductor delivering the fault current, the magnetic flux cancellation decreases. This increases the impedance of the fault path and delays operation of the protective device.

  6. #6
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    I copy that from ET forum, its a bit lengthy but worth getting your mind around. Describes proper grounding to some extent.

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