Being a Mobile Marine Mechanic means that you live at the end of an extension cord. Besides a gas generator, my work truck carries over 500ft of 120v extension cord. Unfortunately, they are often hooked end to end. I carry 200ft. of 10ga., and the rest is 12ga. but as you can tell by the chart below, this is well below the load carrying capacity to run two or more major power tools at one time. And you should never try to pop over an air-conditioning system on a boat at that length.
   Grounded tools require a three wire extension cord. Double insulated tools can use either a two or three wire extension c
ord. (but the three wire  is preferred, for without it you don't have ground fault protection)

Note:  Never go near the water without three wire extension with built in ground fault or remote ground fault. There are still a lot of marinas on the water who don't utilize ground fault at the dock.

  As the distance from the supply outlet increases, you must use a heavier gauge extension cord. Using extension cords with inadequately sized wire causes a serious drop in voltage, resulting in loss of power and possible tool damage. Refer to the table below to determine the required minimum size wire.
Note: Do Not use this table for continuous under-load shore power cords. And never use a standard extension cord as a shore power cord.

  Recommended Minimum Wire Gauge for Extension Cords*
                 Extension Cord Length
25' 50' 75' 100' 150' 200'
0-5 16 16 16 14 12 12
5.1-8 16 16 14 12 10
8.1 - 12 14 14 12 10
12.1-15 12 12 10 10
15.1 - 20 10 10 10

*Based on limiting the line voltage drop to five volts at 150" of the rated amperes.

  The smaller the gauge number of the wire, the greater the capacity of the cord. For example, a 14 gauge cord can carry a higher current than a 16 gauge cord. When using more than one extension on cord to make up the total length, be sure each cord contains at least the minimum wire size required. If you are using one extension cord for more than one tool, add the nameplate amperes and use the sum to determine the required minimum wire size.


Guidelines for Using Extension Cords

  If you are using an extension cord outdoors, be sure it is marked with the suffix "W-A" ("W" in Canada) to indicate that it is acceptable for outdoor use.

  Be sure your extension cord is properly wired and in good electrical condition. Always replace a damaged extension cord or have it repaired by a qualified person before using it.

  Protect your extension cords from sharp objects, excessive heat, and damp or wet areas.


(Grounded Tools: Tools with Three Prong Plugs )

  Tools marked "Grounding Required' have a three wire cord and three prong grounding plug. The plug must be connected to a properly grounded outlet. (see Figure A) If the tool should electrically malfunction or breakdown, grounding provides a low resistance path to carry electricity away from the user, reducing the risk of electric shock.

  The grounding prong in the plug is connected through the green wire inside the cord to the grounding system in the tool. The green wire in the cord must be the only wire connected to the tool's grounding system and must never be attached to an electrically 'live' terminal.

  Your tool must be plugged into an appropriate outlet, properly installed and grounded in accordance with all codes and ordinances. The plug and outlet should look like those in Figure A.

  Figure B illustrates a temporary adapter available for connecting grounded plugs (Figure A) to two prong outlets. The green rigid ear or lug extending from the adapter must be connected to a permanent ground such as a properly grounded outlet box or receptacle. Simply remove the center screw from the outlet, insert the adapter and reattach the screw through the green grounding ear to the outlet if in doubt of proper grounding, call a qualified electrician. A temporary adapter should only be used until a properly grounded outlet can be installed by a qualified electrician. The Canadian Electrical Code prohibits the use of temporary adapters.

WARNING! Improperly connecting the grounding wire can result in the risk of electric shock. Check with a qualified electrician if you are in doubt as to whether the outlet is properly grounded. Do not modify the plug provided with the tool. Never remove the grounding prong from the plug. Do not use the tool if the cord or plug is damaged. If damaged, have it repaired by a service facility before use. If the plug will not fit the outlet, have a proper outlet installed by a qualified electrician.



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