O.T. Electrical Question

Guys,
what is the proper way to ground a whole house stand by generator.The NEC code Section 250.34 is very confussing.

If it has 4 wires then it's grounded though the house system if 3 wires then drive a grounding rod in beside it there should be a place on the generator to hook up the ground wire that should a number bare copper wire.
Walt

You may get some better answers here, but code enforcement varies
from state to state, county to county.
I would check with your local inspector or a licensed master electrician in your area.

The NEC Code book is confusing, no doubt. It's a legal document, not a text book. However any one of the various NEC Code HANDBOOKS is full of pictures, to clarify all this stuff, may show just what you're looking for. Go to a big bookstore, they ought to have one you could snoop through.

Depends on your local inspector but.... There should be a 10ft ground rod at the generator bonded to the chassis with #6 copper. There should also be #6 copper from the generator back to the buildings ground rods/main service ground lug.
Depending on the transfer switch being two or three pole , the generator floating or bonded, the wiring to the main panel and the local inspectors. The ground and neutral connections have to be done properly to prevent neutral current from traveling ground rod to ground rod.
Not supposed to be neutral current on the ground system.

The answer depends whether its a "seperately derived system" or not.

SIDE NOTE BEFORE WE PROCEED just in case one wonders: If a genny is used to power plug and cord connected equipment from on board mounted receptacles, the gennys Neutral to case/frame bond should remain intact and theres no requirement for an external Grounding Electrode connection BUT if local authority says otherwise then do what they say NOT anyone here lol

AND MORE IMPORTANT THE ANSWER DEPENDS UPON WHAT THE LOCAL AUTHORITY SAYS NOTTTTTTTTTT MYSELF OR ANYONE HERE (professional or lay persons) SO BEST CONSULT WITH THEM OVER ANY OF US

(In the comments below Im talking about a typical residential home service of 120/240 volt single phase three wire)

1) If you want to use ONLY a 2 pole transfer switch, i.e. YOU DO NOT SWITCH THE NEUTRAL only the two hots, the gennys Neutral to case/frame bond is severed,,,,,,,,The Gennys Neutral and Utility Neutrals are bonded together,,,,,,,,The safety equipment GroundING conductor is carried out and bonded to the gennys now floating (NOT bonded to Neutral remember) case/frame.

2) If you use a 3 pole transfer switch, i.e. the Neutral plus the 2 hots are switched, the gennys Neutral to case/frame bond remains in place and the Neutral/Case/Frame is all tied to a Grounding Electrode Conductor (like bare No 4 copper wire) which leads to a proper approved Grounding Electrode such as driven rod or rods or water pipes etc etc

My best free and worth the same (NOTHING) advice would be to consult with your local Utility Provider and any local governing authority AND AGAIN DO AS THEY SAY OVER ANYTHING ANYONE HERE, LAY OR PROFESSIONAL, MIGHT THINK. Ive been retired as an EE tooooooo longgggggggg and am rusty as an old nail on the latest NEC so NO WARRANTY on my opinions either, but its still my best faith and best remembered way to correctly earth ground a household generator, PLEASE see what the other professional electricians and engineers and technicians have to say also. For the 1,000 time (I so enjoy posting this every time lol) beware of taking advice from Billy Bob and his know it all brother in law Bubba who wired their own homes over a case of beer and everything works so they must be experts lol


Keep safe, consult with your Utility Provider and Local Authority, it may save their and/or you and your familys lives.

John T Tooooo longggggggg retired EE

According to the way the gov installers interpet it. If its a STAND ALONE system,it gets a grounding rod ,frame is bonded etc. If its a BACKUP system, in other words only starts and runs when commercial power fails,it uses the commercial power ground,generally installed at the meter base, and frame bonding straps are lifted. Thats how we do all of our systems anyway,and as I interpet it thats what the code book says. Just as a side note: Normal power on a system here would be commercial power,failing to generator power, failing to battery bank power. Normally two,three or more power supplies, sometimes two or more independant backup battery banks ,and often transfer switches that dont break before closing for use in brownout conditions. It can get very confusing,if you dont keep grounds all single point, and ground loops can kill you. We do of course use multipoint grounds on some systems but for the most part power systems use single point grounds. In other words you normally want all power generating systems grounded to the same point. Basically, it keeps multi powered systems from floating several volts above one another. A transformer for instance can be several thousand volts above a backup generators voltage if its not properly ground referenced. It can get very complicated, but if you use a single point as your ground reference,its much much less so.

According to the way the gov installers interpet it. If its a STAND ALONE system,it gets a grounding rod ,frame is bonded etc. If its a BACKUP system, in other words only starts and runs when commercial power fails,it uses the commercial power ground,generally installed at the meter base, and frame bonding straps are lifted. Thats how we do all of our systems anyway,and as I interpet it thats what the code book says. Just as a side note: Normal power on a system here would be commercial power,failing to generator power, failing to battery bank power. Normally two,three or more power supplies, sometimes two or more independant backup battery banks ,and often transfer switches that dont break before closing for use in brownout conditions. It can get very confusing,if you dont keep grounds all single point, and ground loops can kill you. We do of course use multipoint grounds on some systems but for the most part power systems use single point grounds. In other words you normally want all power generating systems grounded to the same point. Basically, it keeps multi powered systems from floating several volts above one another. A transformer for instance can be several thousand volts above a backup generators voltage if its not properly ground referenced. It can get very complicated, but if you use a single point as your ground reference,its much much less so.

Pretty much the message we have trying to preach here. The entire service on the customer side of the meter should only have one earth bond to the neutral as near as possible/onside the first service panel.
All ground rods and panel ground bars should be connected at all panels, generators sub panels , water pipes etc . To make the entire ground system a continuous network.
The neutral treated as the energized live conductor that it is and not connect to earth anywhere else,ever.

Ground and neutral terminate at the same place-ground. (line side) Dont take my word for it, read and look at the diagram. (pic) Without an eventual return to ground (somewhere) electrons will not flow-peroid. No electron flow, no current.
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as a side note, never trust an old water pipe, or support beam thats in the ground as your single source for a ground. It's good to have these things grounded, but always use an approved ground rod at your power sourse.

That source by the way is from "The Bureau of Reclamation", you know, the guys that are in charge of the Hover dam, and all of the Hydroelectric power that comes from there.

(quoted from post at 22:04:22 12/13/12) Ground and neutral terminate at the same place-ground. (line side) Dont take my word for it, read and look at the diagram. (pic) Without an eventual return to ground (somewhere) electrons will not flow-peroid. No electron flow, no current.
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ou are so wrong. Are you a tech , engineer or linesman at a utility company?
The entire system will operate just fine without any grounding system at all. Problem is he secondary side could go to 4.8 or 7.2 KV with a transformer fault.

Some folks would argue with God about how long he took to create the earth. Write the folks that produce electricity. Tell them they're diagrams,text books and codes, schools, teachers, tests, service techs, are all wrong because some guy on the internet said so. If you can't read, at least click on the link, and look at the pictures.

To answer your question: HVAC Tech and Electrician, 30 years

(quoted from post at 00:30:57 12/15/12) To answer your question: HVAC Tech and Electrician, 30 years

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Sorry, you have been wrong for 30 years