GFCI on short extension question....

[DougB]

I bought a GFCI extension cord a few months back. It's about 2-3 foot long with a triple plug on the end and the GFCI works mounted in the middle of th cord's length. Anyway, that stuff may not have anything to do with my question, at least you know what I'm talking about....

I ran a heavy duty extension cord (about 40 feet long) from a standard receptacle in my basement, through a window to the driveway and then plugged the short GFCI cord into that, and then plugged my circular saw into that. A friend who was going to be doing most of the cutting (who is also a union electrician) saw this setup and told me I needed to move the short GFCI cord so it was plugged into the house receptacle and then the heavy duty extension cord could be plugged into it, otherwise, the GFCI would not work. I told him I thought he was wrong, but since he was doing the cutting (free labor, I might add)I would hook it up any way that made him happy.

So now I am just curious, does this make sense? I know I've seen these devices hooked up on jobsites at the end of a long extension cord, just like I had it. And also, I would think if this were true, it would have a big bold warning printed on it saying so.

What do you guys think?

dbunch

[Jim Thompson]

It shouldn't make any difference where the GFCI is located... it measures asymmetrical currents.

...Jim Thompson

[Tekkie]

Jim Thompson posted for all of us....

I think your electrical guy was correct.

In this instance the GFCI is measuring the LOAD side of it's cord. Therefore if there is problem in that short distance between the GFCI & what is plugged into it will be detected, but if there is a problem between the basement outlet & the GFCI it will NOT be detected.

If you plug your GFCI cord into your basement outlet and then your extension cord into that you are effectively increasing the load side length of the GFCI.

[volts500]

It's a safety thing. By putting the GFCI at the source, the extension cord is also protected. _Never_ use a non-GFCI protected extension cord when doing construction work. You never know if the extension cord has been previously damaged or gets cut while work is in progress. If you saw it done the way you described on a jobsite, it was probably to take advantage of 3-way tap (not the GFCI feature) and the extension cord was then plugged into a GFCI protected outlet at the temporary power panel.........if not it's a serious OSHA violation, not soon to be forgotten if one has to pay the fine......or worse, if someone gets seriously injured or killed.

[DougB]

OK, so he was wrong if he was saying the GFCI would not protect him while he was working the saw. But it made sense in that if the extension cord coming through the window got ripped open, it could energize the metal window frame and not kick the GFCI further down the line (although it would probably kick the breaker at the panel).

So it does seem like a good idea to put it at the receptacle rather than at the end of the extension cord.

The use of the 3 outlet splitter is exactly why I thought to put it at the end of the extension could.

This makes me think they should not make the GFCI things with multiple plugs at the end.

Thanks for the information.

dbunch