Posted by John T on June 12, 2016 at 12:10:00 from (216.249.76.23):
In Reply to: GFCI on generator posted by Russ from MN on June 12, 2016 at 08:59:55:
Sorry gents, this is all too complex that there's no way I can explain it in a few sentences, especially to non electricians, but I will lay out a few facts and basics and NEC rules at least. DONT FEEL BAD if you still don't get it, it took me a lot of education and experience before it all sunk in lol
1) SOME small portable gensets use a FLOATING NEUTRAL while OTHER small portable gensets BOND NEUTRAL TO THE CASE/FRAME. That's because the way you use it in conjunction with what transfer switch (how many poles) you use makes a difference if the Neutral should be Floated or Bonded.
2) In the RV and camping and construction world when line device monitors are used that will trip out due to an open Neutral and the genny had a floating Neutral, the FIX is to wire up a plug that has Neutral tied to Ground which turns a Floating Neutral Genset over into one with a bonded Neutral, that way the monitor and protection devices will work.
3) CONTRARY TO LAY OPINION AND URBAN LEGENDS AND OLD WIVES TALES (unless NEC has changed) if you use a portable genset to operate cord and plug tools that are fed from onboard mounted receptacle THERE IS NO NEC NOR SAFETY REQUIREMENT OR REASON the genset be connected to a Grounding Electrode!!!!!!!!!!!!!! If your body gets exposed to 120 VAC Line to Neutral you die regardless if the genset was wired to a copper rod driven into mother earth. ALSO AND VERY IMPORTANT a non Neutral earth grounded genset (Floating) has ZERO NONE ZILCH NADA voltage potential with respect to mother earth, so if you touch the hot even barefooted on wet ground theres no shock but you still get shocked if you get across Line and Neutral. HOWEVER your home utility DOES HAVE NEUTRAL BONDED TO EARTH so if you touch a hot wire standing on bare ground you do get shocked.
4) If you think stickling a screwdriver down into the earth is going qualify as a proper NEC "Grounding Electrode" or serve the identical purpose or "protect you and save your life" compared to one or two 8 ft driven copper rods GOOD LUCK WITH THAT ONE LOL.
FIRST OF ALL the earth is a poor conductor subject to iron and minerals and salts and moisture etc etc which is why the 'ground" is tested to see if a second rod is required in some jurisdictions SECOND OF ALL the portable genset you think you are "grounding" (yeah right) may or may not even have a bonded Neutral, so how does it save your life by wiring the genset to a screwdriver into the earth?????????????????????????? What good do you think that does anyhow???
5) The way a GFCI works is to pass HOT and NEUTRAL through a Torroidal Coil. If ALLLLL the current flowing out the HOT is returned in the NEUTRAL no voltage is induced so no GFCI trip. HOWEVER if as little as 5 milliamps of current is NOT returned via the Neutral but your body or earth or ground or elsewhere voltage is induced so it trips to save your life. It takes something like 30 to 50 milliamps to fibrillate the heart so 5 ma is the GFCI trip current.
6) AS LONG AS the GFCI passes HOT and NEUTRAL through the torroid it will function REGARDLESS IF THERES AN EARTH GROUND AT THE GENSET (or screwdriver in ground lol) OR NOT REGARDLESS IF THERES A GROUNDING ELECTRODE CONDUCTOR (3rd wire in cord out to tool) OR NOT (still works on a 2 wire plug) HOWEVER the self test push button feature may not work
7) When using a portable genset if youre worried about being on wet earth YOURE BETTER OFF AND SAFER if theres NO VOLTAGE WITH RESPECT TO EARTH ON ANY OF THE WIRES!!!!!!!!!!!!!!!!!!! 1) It may NOT EVEN HAVE A BONDED NEUTRAL IN THE FIRST PLACE so driving a rod into earth is absolutely NO HELP. 2) If it has a bonded to earth Neutral and you're on wet ground and you touch a hot wire YOU GET SHOCKED. If you accidentally touch a wire and youre barefooted on wet ground WOULDNT YOU PREFER THERES NO VOLTAGE ON THAT WIRE RELATIVE TO EARTH GROUND??????????????????????
NUFF SAID, don't feel bad if you don't understand this, go get some books and read up and study because its still NOT rocket science (maybe to Billy Bob and Bubba lol) and makes sense once you understand the basics.
NOTE don’t get me wrong, there are situations THAT DO REQUIRE A GENSET BE BONDED AND GROUNDED (such as if its configured as a “Separately Derived Source”) , I just addressed certain limited situations above not alllllllllllllllllllll READ THE NEC
John T Long retired electrical power distribution engineer and rusty so no warranty
NOTE just because some inspectors (many NOT engineers) MAY NOT understand this, that don't mean they still don't rule, you have to do as they say just like the grouchy lady at the license branch lol
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