I will be installing a standby generator located about 50 ft. from the
grounding rod for my house. If I ground the generator only in main panel,
then there is a possibility that the generator frame will be at a slightly
different potential than the adjacent earth on which someone touching the
generator may be standing. If I install a ground rod at the generator
location, then I will be introducing a ground loop with its associated
problems.

How, according to the NEC, should the generator be grounded? Please
provide a code reference (or quote) if you can.

Many thanks for any help.

On Sep 7, 1:35*pm, wrote:
I will be installing a standby generator located about 50 ft. from the
grounding rod for my house. *If I ground the generator only in main panel,
then there is a possibility that the generator frame will be at a slightly
different potential than the adjacent earth on which someone touching the
generator may be standing. *If I install a ground rod at the generator
location, then I will be introducing a ground loop with its associated
problems.

How, according to the NEC, should the generator be grounded? *Please
provide a code reference (or quote) if you can.

Many thanks for any help.

Ground the frame where it is installed

wrote in message
...
I will be installing a standby generator located about 50 ft. from the
grounding rod for my house. If I ground the generator only in main panel,
then there is a possibility that the generator frame will be at a slightly
different potential than the adjacent earth on which someone touching the
generator may be standing. If I install a ground rod at the generator
location, then I will be introducing a ground loop with its associated
problems.

How, according to the NEC, should the generator be grounded? Please
provide a code reference (or quote) if you can.

Many thanks for any help.


There should be grounding requirements in the installation instructions.
Generally there is an external ground lug on the frame or housing of the
generator. This would get connected to your grounding electrode conductor
for lightning protection. There should also be an equipment grounding
conductor that is run with generator conductors to the transfer switch or
panel that you will be supplying the generator power to.

John Grabowski wrote:


There should be grounding requirements in the installation
instructions. Generally there is an external ground lug on the frame
or housing of the generator. This would get connected to your
grounding electrode conductor for lightning protection. There should
also be an equipment grounding conductor that is run with generator
conductors to the transfer switch or panel that you will be supplying
the generator power to.

Lightning protection? You got wire that'll handle 7,000 Amps?

"HeyBub" wrote in message
m...
John Grabowski wrote:


There should be grounding requirements in the installation
instructions. Generally there is an external ground lug on the frame
or housing of the generator. This would get connected to your
grounding electrode conductor for lightning protection. There should
also be an equipment grounding conductor that is run with generator
conductors to the transfer switch or panel that you will be supplying
the generator power to.

Lightning protection? You got wire that'll handle 7,000 Amps?


LOL. What do you think ground rods are for? For a generator a #10 may only
be required. For a house a #6 or #4 will suffice.

On Sep 7, 4:08*pm, "John Grabowski" wrote:
wrote in message

...

I will be installing a standby generator located about 50 ft. from the
grounding rod for my house. *If I ground the generator only in main panel,
then there is a possibility that the generator frame will be at a slightly
different potential than the adjacent earth on which someone touching the
generator may be standing. *If I install a ground rod at the generator
location, then I will be introducing a ground loop with its associated
problems.

How, according to the NEC, should the generator be grounded? *Please
provide a code reference (or quote) if you can.

Many thanks for any help.

There should be grounding requirements in the installation instructions.
Generally there is an external ground lug on the frame or housing of the
generator. *This would get connected to your grounding electrode conductor
for lightning protection. *There should also be an equipment grounding
conductor that is run with generator conductors to the transfer switch or
panel that you will be supplying the generator power to.

The gen only needs small wire attached to even a long nail driven into
the ground, a lightning rod is overkill

Lightning protection? You got wire that'll handle 7,000 Amps?


Actually up to a record 200,000 amps has been measured, however it lasts
for only about a millisecond so the wire will not heat appreciably during
that short time.

Most commonly, the lightning current ceases in about a millisecond for a
given stroke, but sometimes there is a continuing current on the order of
100 amps following one or more of the strokes. This is called "hot
lightning" and it is the cause of lightning fires. The continuing current
only lasts for only 0.2 seconds and so a typical ground wire is sufficient.

"ransley" wrote in message
...
On Sep 7, 4:08 pm, "John Grabowski" wrote:
wrote in message

...

I will be installing a standby generator located about 50 ft. from the
grounding rod for my house. If I ground the generator only in main
panel,
then there is a possibility that the generator frame will be at a
slightly
different potential than the adjacent earth on which someone touching
the
generator may be standing. If I install a ground rod at the generator
location, then I will be introducing a ground loop with its associated
problems.

How, according to the NEC, should the generator be grounded? Please
provide a code reference (or quote) if you can.

Many thanks for any help.

There should be grounding requirements in the installation instructions.
Generally there is an external ground lug on the frame or housing of the
generator. This would get connected to your grounding electrode conductor
for lightning protection. There should also be an equipment grounding
conductor that is run with generator conductors to the transfer switch or
panel that you will be supplying the generator power to.

The gen only needs small wire attached to even a long nail driven into
the ground, a lightning rod is overkill



LOL. You guys are making me laugh tonight. Thanks. This reminds of the
person a few years back who posted about sticking a wire from her computer
out the window to a coat hanger in the ground because her house was not a
grounded system.

Maybe on the next job I'll connect a ground wire good for 7000 amps to a
long nail and show the inspector this thread. LOL

I really do appreciate all you folks who took the time to reply. However,
the subject began "code question" amd so far none of the replies have tried
to answer the question based on code. Also the question asked was "How,
according to the NEC, should the generator be grounded?" Does anyone have
an answer based upon their knowledge of the NEC?

As to the long nail suggestion you may be very certain that the nail will
not be connected well to the ground when it is new and much less so after
it begins to rust. That is why long ground rods are used and why two are
sometimes required. That is also why they are made of copper. Yes the
outside of the copper will corrode but the copper oxide, unlike rust, is
conductive.

On Sep 7, 11:35*am, wrote:
I will be installing a standby generator located about 50 ft. from the
grounding rod for my house. *If I ground the generator only in main panel,
then there is a possibility that the generator frame will be at a slightly
different potential than the adjacent earth on which someone touching the
generator may be standing. *If I install a ground rod at the generator
location, then I will be introducing a ground loop with its associated
problems.

How, according to the NEC, should the generator be grounded? *Please
provide a code reference (or quote) if you can.

Many thanks for any help

Grounding and bonding depend on whether or not is a seperatley derived
system or not. I assume you are permanantly mounting the generator
and it is not a portable unit. I also assume you are installing a
transfer switch. Is this correct? NEC 2005 Article 250 is where to
look.

John Grabowski wrote:
"HeyBub" wrote in message
m...
John Grabowski wrote:


There should be grounding requirements in the installation
instructions. Generally there is an external ground lug on the frame
or housing of the generator. This would get connected to your
grounding electrode conductor for lightning protection. There
should also be an equipment grounding conductor that is run with
generator conductors to the transfer switch or panel that you will
be supplying the generator power to.

Lightning protection? You got wire that'll handle 7,000 Amps?


LOL. What do you think ground rods are for? For a generator a #10
may only be required. For a house a #6 or #4 will suffice.

Well, they sure as hell ain't for lightning protection!

wrote:
I will be installing a standby generator located about 50 ft. from the
grounding rod for my house. If I ground the generator only in main panel,
then there is a possibility that the generator frame will be at a slightly
different potential than the adjacent earth on which someone touching the
generator may be standing. If I install a ground rod at the generator
location, then I will be introducing a ground loop with its associated
problems.

How, according to the NEC, should the generator be grounded? Please
provide a code reference (or quote) if you can.

Many thanks for any help.
I wrestled with this about a decade ago and at that time couldn't find a
clear reference in the NEC. The intent of the NEC seemed to too
establish a good single point ground at the entrance panel/meter base.
I did this with two ground rods (10 ft as I recall) at the mater
base. The run to the entrance panel is about 15 ft further inside my
basement. I have six subpanels, and none of these are grounded...all
neutrals tie back to the entrance panel.

My generator is located at the other end of my house, about 150 ft away.
I have a 10 ft ground rod at the generator to which the generator is
connected and a single #4 stranded copper wire, perhaps 200 ft long,
buried along the perimeter of the basement that bonds this ground rod to
the two ground rods at the meter base. At the time I did this I felt
that I was in compliance with the NEC (although today I can't cite a
specific reference.)

On Sun, 7 Sep 2008 18:34:22 -0700 (PDT), wrote:

Grounding and bonding depend on whether or not is a seperatley derived
system or not. I assume you are permanantly mounting the generator
and it is not a portable unit. I also assume you are installing a
transfer switch. Is this correct? NEC 2005 Article 250 is where to
look.

It is a permanent installation. I will not be using a transfer switch. I
will be backfeeding the panel through one of the breakers. That breaker
has a mechanical interlock which prevents both it and the main breaker
being on at the same time. (It is impossible to turn on the backfeed
breaker on unless the main is off, and impossible to turn the main breaker
on unless the backfeed breaker is off.)

Thanks for the code reference.

"HeyBub" wrote in message
m...
John Grabowski wrote:
"HeyBub" wrote in message
m...
John Grabowski wrote:


There should be grounding requirements in the installation
instructions. Generally there is an external ground lug on the frame
or housing of the generator. This would get connected to your
grounding electrode conductor for lightning protection. There
should also be an equipment grounding conductor that is run with
generator conductors to the transfer switch or panel that you will
be supplying the generator power to.

Lightning protection? You got wire that'll handle 7,000 Amps?


LOL. What do you think ground rods are for? For a generator a #10
may only be required. For a house a #6 or #4 will suffice.

Well, they sure as hell ain't for lightning protection!



LOL. I printed this thread to show some of my fellow electricians. They
will get a good laugh like I did. Thanks for making my week.

On Sun, 07 Sep 2008 22:05:03 -0400, wrote Re Code
question on generator grounding:

That breaker
has a mechanical interlock which prevents both it and the main breaker
being on at the same time. (It is impossible to turn on the backfeed
breaker on unless the main is off, and impossible to turn the main breaker
on unless the backfeed breaker is off.)

Where do you get such an interlock? Do you have a product name &
manufacturer? Even better, do you have a link?

Thanks

Caesar Romano wrote:
On Sun, 07 Sep 2008 22:05:03 -0400, wrote Re Code
question on generator grounding:

That breaker
has a mechanical interlock which prevents both it and the main
breaker being on at the same time. (It is impossible to turn on the
backfeed breaker on unless the main is off, and impossible to turn
the main breaker on unless the backfeed breaker is off.)

Where do you get such an interlock? Do you have a product name &
manufacturer? Even better, do you have a link?


They differ by panel model within manufacturer and are all hideously
expensive. Here's what I did on a Square D panel.

The connection to the generator goes to a double circuit breaker located in
the upper right column. For normal, non-emergency, operation, this breaker
is OFF.

It's possible to fashion a metal or plexiglass plate that nudges against
both the main circuit switch and this odd circuit breaker. This plate is
bolted to the panel cover via elongated holes in the plate that allow the
plate to slide, making contact with the two switch handles. The trick is to
match the sliding with the positions of the main switch and the odd breaker.
The breaker can't be turned ON unless the main switch is OFF. The main
switch can't be turned ON unless the breaker is OFF.

On a Square D, main switch ON is to the right and circuit breaker OFF is to
the right. If you have a block plate between the levers, it's obvious the
circuit breaker can't be moved to the left (ON) unless the main is first
moved to the left (OFF) and the blocking plate moved likewise. Similarily,
the main can't be moved right (ON) unless the circuit breaker is first moved
right (OFF) and the blocking plate scooted over with it.

Get the model and make of your panel and do a search on "{make} {model}
interlock" The results will give you an idea of how the manufacturer of your
panel wants the thing to work. You can then either find the best price on
the "approved" device or, as I did, fashion your own.

Some of the panel makers make them. Square D makes them for their Q0
panels and I think they now have them for their Homeline panels. Others
also have them.

Google "generator interlock kit" or see http://www.interlockkit.com/

On Mon, 08 Sep 2008 07:38:29 -0500, Caesar Romano wrote:

On Sun, 07 Sep 2008 22:05:03 -0400, wrote Re Code
question on generator grounding:

That breaker
has a mechanical interlock which prevents both it and the main breaker
being on at the same time. (It is impossible to turn on the backfeed
breaker on unless the main is off, and impossible to turn the main breaker
on unless the backfeed breaker is off.)

Where do you get such an interlock? Do you have a product name &
manufacturer? Even better, do you have a link?

Thanks

On Mon, 8 Sep 2008 09:54:16 -0500, "HeyBub"
wrote Re Code question on generator grounding:

Get the model and make of your panel and do a search on "{make} {model}
interlock" The results will give you an idea of how the manufacturer of your
panel wants the thing to work. You can then either find the best price on
the "approved" device or, as I did, fashion your own.

Thanks for the detailed description. I can easily visualize the
"field" modification that you made. Very creative. Nice going.

On Mon, 08 Sep 2008 11:02:09 -0400, wrote Re Code
question on generator grounding:

Some of the panel makers make them. Square D makes them for their Q0
panels and I think they now have them for their Homeline panels. Others
also have them.

Google "generator interlock kit" or see http://www.interlockkit.com/

Thanks!

It looks like it can be an interesting "home-made" project:

1) Make a template out of cardboard

2) Use the cardboard template to fabricate a working interlock from
1/8" aluminum plate.

John Grabowski wrote:


"HeyBub" wrote in message
m...
John Grabowski wrote:


There should be grounding requirements in the installation
instructions. Generally there is an external ground lug on the frame
or housing of the generator. This would get connected to your
grounding electrode conductor for lightning protection. There should
also be an equipment grounding conductor that is run with generator
conductors to the transfer switch or panel that you will be supplying
the generator power to.

Lightning protection? You got wire that'll handle 7,000 Amps?


LOL. What do you think ground rods are for? For a generator a #10 may
only
be required. For a house a #6 or #4 will suffice.


This was my question as I read this thread. The OP said something about
standing next to the generator and having different potential. But my
understanding about "grounding" in this case is that its about lightning.
I don't think there will be any current flow from the generator through a
person's feet and into the soil no matter how its wired or what he touches.
Is that correct?


CLG

I did this in my previous house before interlock kits were available. It
was not hard and worked very well. After checking the cost of the kits
(ridiculous!) I plan to do it again, esp. since I have two 200 Amp panels,
the kits would cost $300 to $400 depending on where you bought them.

In my situation, I do not want a gen large enough to power the whole house
so I won't use autostart anyway. I will manually turn off the HVAC brakers
before starting the gen. Then everything else in my house will have power
available, even if I cannot run it all at the same time.

I had a 6KW gen hooked up this way before. Had a 21 day power outage and
another 10+ day power outage and never a moment's trouble and no overloads
of tripped breakers occurred. Saved a lot of $$$ on fuel by not having a
huge generator.

On Mon, 08 Sep 2008 10:38:11 -0500, Caesar Romano wrote:

On Mon, 08 Sep 2008 11:02:09 -0400, wrote Re Code
question on generator grounding:

Some of the panel makers make them. Square D makes them for their Q0
panels and I think they now have them for their Homeline panels. Others
also have them.

Google "generator interlock kit" or see http://www.interlockkit.com/

Thanks!

It looks like it can be an interesting "home-made" project:

1) Make a template out of cardboard

2) Use the cardboard template to fabricate a working interlock from
1/8" aluminum plate.

On Mon, 08 Sep 2008 12:55:34 -0400, wrote Re Code
question on generator grounding:

I did this in my previous house before interlock kits were available. It
was not hard and worked very well. After checking the cost of the kits
(ridiculous!) I plan to do it again, esp. since I have two 200 Amp panels,
the kits would cost $300 to $400 depending on where you bought them.

You have two 200A panels in one house? Or is one of the panels in a
work shop building?


I had a 6KW gen hooked up this way before. Had a 21 day power outage and
another 10+ day power outage and never a moment's trouble and no overloads
of tripped breakers occurred. Saved a lot of $$$ on fuel by not having a
huge generator.

I've have a similar configuration and experience with a couple of 10+
day outages.

On Mon, 08 Sep 2008 13:11:23 -0500, Caesar Romano wrote:

You have two 200A panels in one house? Or is one of the panels in a
work shop building?

This is standard for homes with 400 Amp service.

On Mon, 08 Sep 2008 12:55:34 -0400, wrote:

(ridiculous!) I plan to do it again, esp. since I have two 200 Amp panels,

Your house must be way cool!

In my situation, I do not want a gen large enough to power the whole house
so I won't use autostart anyway. I will manually turn off the HVAC brakers
before starting the gen. Then everything else in my house will have power
available, even if I cannot run it all at the same time.

I don't understand why anyone would want to select the circuits on the
generator. To me, having the whole panel on the generator would be
much easier to set up and much more flexible.

If the generator doesn't auto start, and I have never seen one that
did, then you can shed which loads you want to lock out, and the
family knows to be careful when the power is out.

The one time the daughter uses the blow dryer, and everything goes
dark would be enough reminder. The breaker lets you safely test the
limits.

On Mon, 8 Sep 2008 09:54:16 -0500, "HeyBub"
wrote Re Code question on generator grounding:

Get the model and make of your panel and do a search on "{make}
{model} interlock" The results will give you an idea of how the
manufacturer of your panel wants the thing to work. You can then
either find the best price on the "approved" device or, as I did,
fashion your own.

Thanks for the detailed description. I can easily visualize the
"field" modification that you made. Very creative. Nice going.

But you had better check your local codes. It's likely they will not
allow that setup. NEC et al are only starting points; then the local
guys get into the act and add their own idiocy, I mean, opinions of how
things should be.
KNOW BEFORE DOING is the proper mantra. Otherwise you could be doing
it more than once.

On Mon, 08 Sep 2008 16:52:13 -0400, metspitzer
wrote:



I don't understand why anyone would want to select the circuits on the
generator. To me, having the whole panel on the generator would be
much easier to set up and much more flexible.

But this is what you have to do if you use a transfer switch/panel that has
only a few circuits. That's why I plan to backfeed the main panels.

On Mon, 08 Sep 2008 23:48:06 -0400, wrote Re Code
question on generator grounding:

On Mon, 08 Sep 2008 16:52:13 -0400, metspitzer
wrote:



I don't understand why anyone would want to select the circuits on the
generator. To me, having the whole panel on the generator would be
much easier to set up and much more flexible.

But this is what you have to do if you use a transfer switch/panel that has
only a few circuits. That's why I plan to backfeed the main panels.

Indeed, having the generator feed the entire panel is the way to go.
That gives you the flexibility to choose which loads to feed at the
time you need to use the generator.

On Mon, 8 Sep 2008 20:04:46 -0400, "TWayne"
wrote Re Code question on generator
grounding:

Thanks for the detailed description. I can easily visualize the
"field" modification that you made. Very creative. Nice going.

But you had better check your local codes. It's likely they will not
allow that setup. NEC et al are only starting points; then the local
guys get into the act and add their own idiocy, I mean, opinions of how
things should be.
KNOW BEFORE DOING is the proper mantra. Otherwise you could be doing
it more than once.

Very true. However I am fortunate enough to live in a rural area not
subject to codes. Nevertheless I generally do my own projects to code
where the code make sense.