Â* When is it necessary ? I've just replaced the panel out in the shop
(aluminum buss bars on the old one were giving problems) and I have a 3
wire service run out there . At this time the only place the neutral is
bonded to ground is in the meter box . It has been suggested to me to
bond them in the main panel too ... but that seems redundant to me ,
they're only the thickness of a piece of plywood apart . I have
considered installing a ground rod at the new panel but am concerned
about the potential for ground loop currents .

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !

On Sun, 9 Jun 2019 20:01:54 -0500, Terry Coombs
wrote:


* When is it necessary ? I've just replaced the panel out in the shop
(aluminum buss bars on the old one were giving problems) and I have a 3
wire service run out there . At this time the only place the neutral is
bonded to ground is in the meter box . It has been suggested to me to
bond them in the main panel too ... but that seems redundant to me ,
they're only the thickness of a piece of plywood apart . I have
considered installing a ground rod at the new panel but am concerned
about the potential for ground loop currents .
by cide the seb has to be "floating" - the neutral and ground bonded
pnly at one point DOWNSTREAM OF THE MAIN DISCONNECT. The main panel
gets "bonded" - nothuing else does - including a connected generator

On Sun, 9 Jun 2019 20:01:54 -0500, Terry Coombs
wrote:


* When is it necessary ? I've just replaced the panel out in the shop
(aluminum buss bars on the old one were giving problems) and I have a 3
wire service run out there . At this time the only place the neutral is
bonded to ground is in the meter box . It has been suggested to me to
bond them in the main panel too ... but that seems redundant to me ,
they're only the thickness of a piece of plywood apart . I have
considered installing a ground rod at the new panel but am concerned
about the potential for ground loop currents .



What's the question again ?
seriously ...
John T.

On Sun, 9 Jun 2019 20:01:54 -0500, Terry Coombs
wrote:


Â* When is it necessary ? I've just replaced the panel out in the shop
(aluminum buss bars on the old one were giving problems) and I have a 3
wire service run out there . At this time the only place the neutral is
bonded to ground is in the meter box . It has been suggested to me to
bond them in the main panel too ... but that seems redundant to me ,
they're only the thickness of a piece of plywood apart . I have
considered installing a ground rod at the new panel but am concerned
about the potential for ground loop currents .

If you only have 3 wires in the feeder going to the shop you need to
bond the neutral and ground out there too or there is no path for
fault current. You also need a ground electrode out there. Current
code requires a 4 wire feeder and isolating neutral and ground in sub
panels but if the wire was already there when the 1996 code was
adopted the 3 wire feeder is grandfathered in.
Ground loops are not an issue but carrying circuit current in the
grounding conductor is, That is why you do need another ground
electrode. Essentially you are creating another service in the second
building and creating a new ground reference there.
In the electrical biz, you can't have too many ground electrodes but
they all need to be bonded together.

On Sun, 09 Jun 2019 21:37:01 -0400, Clare Snyder
wrote:

On Sun, 9 Jun 2019 20:01:54 -0500, Terry Coombs
wrote:


Â* When is it necessary ? I've just replaced the panel out in the shop
(aluminum buss bars on the old one were giving problems) and I have a 3
wire service run out there . At this time the only place the neutral is
bonded to ground is in the meter box . It has been suggested to me to
bond them in the main panel too ... but that seems redundant to me ,
they're only the thickness of a piece of plywood apart . I have
considered installing a ground rod at the new panel but am concerned
about the potential for ground loop currents .
by cide the seb has to be "floating" - the neutral and ground bonded
pnly at one point DOWNSTREAM OF THE MAIN DISCONNECT. The main panel
gets "bonded" - nothuing else does - including a connected generator

You float the neutral if you have a 4 wire feeder but if you are still
working with that older 3 wire feeder, you need to reground the
neutral. That was only legal in a second building. In a single
building, all sub panels needed a 4 wire feeder and always have.

Generators will depend on what transfer equipment you are using. If
you switch the neutral, the generator is a separately derived system
and you bond the neutral since the main bonding jumper in the service
disconnect is not in the system anymore.

On 6/9/2019 9:40 PM, wrote:
On Sun, 9 Jun 2019 20:01:54 -0500, Terry Coombs
wrote:

Â* When is it necessary ? I've just replaced the panel out in the shop
(aluminum buss bars on the old one were giving problems) and I have a 3
wire service run out there . At this time the only place the neutral is
bonded to ground is in the meter box . It has been suggested to me to
bond them in the main panel too ... but that seems redundant to me ,
they're only the thickness of a piece of plywood apart . I have
considered installing a ground rod at the new panel but am concerned
about the potential for ground loop currents .
If you only have 3 wires in the feeder going to the shop you need to
bond the neutral and ground out there too or there is no path for
fault current. You also need a ground electrode out there. Current
code requires a 4 wire feeder and isolating neutral and ground in sub
panels but if the wire was already there when the 1996 code was
adopted the 3 wire feeder is grandfathered in.
Ground loops are not an issue but carrying circuit current in the
grounding conductor is, That is why you do need another ground
electrode. Essentially you are creating another service in the second
building and creating a new ground reference there.
In the electrical biz, you can't have too many ground electrodes but
they all need to be bonded together.


Â* OK , that makes sense . I'll need to drive a rod and run the ground
wire into the box . I can put it in the hole thru the concrete floor
that the service feed comes up through . And I just happen to have the
ground rod and wire from when I pulled out the temp service pole . I
considered using the metal carport frame , but that might be dangerous
under certain dry soil conditions .

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !

On Sun, 9 Jun 2019 22:39:34 -0500, Terry Coombs
wrote:

On 6/9/2019 9:40 PM, wrote:
On Sun, 9 Jun 2019 20:01:54 -0500, Terry Coombs
wrote:

Â* When is it necessary ? I've just replaced the panel out in the shop
(aluminum buss bars on the old one were giving problems) and I have a 3
wire service run out there . At this time the only place the neutral is
bonded to ground is in the meter box . It has been suggested to me to
bond them in the main panel too ... but that seems redundant to me ,
they're only the thickness of a piece of plywood apart . I have
considered installing a ground rod at the new panel but am concerned
about the potential for ground loop currents .
If you only have 3 wires in the feeder going to the shop you need to
bond the neutral and ground out there too or there is no path for
fault current. You also need a ground electrode out there. Current
code requires a 4 wire feeder and isolating neutral and ground in sub
panels but if the wire was already there when the 1996 code was
adopted the 3 wire feeder is grandfathered in.
Ground loops are not an issue but carrying circuit current in the
grounding conductor is, That is why you do need another ground
electrode. Essentially you are creating another service in the second
building and creating a new ground reference there.
In the electrical biz, you can't have too many ground electrodes but
they all need to be bonded together.


Â* OK , that makes sense . I'll need to drive a rod and run the ground
wire into the box . I can put it in the hole thru the concrete floor
that the service feed comes up through . And I just happen to have the
ground rod and wire from when I pulled out the temp service pole . I
considered using the metal carport frame , but that might be dangerous
under certain dry soil conditions .

Until you get a local ground electrode out there I would be careful
bonding anything. It is best to drive 2 rods 6 feet or more apart.
That is about all you are going to get out of a rod electrode.
Rods are not really that good though. The best is probably a concrete
encased electrode, the rebar in your foundation. Next would be a
ground ring, a buried wire all the way around the building. Back in
the olden days we had the best electrode around when all of the
underground water pipe was metal and everyone had a metal to metal
connection all the way back to the water plant. There were cases where
the neutrals were totally gone and nobody noticed because they gut a
path through all of that water pipe back to somebody who had a good
neutral.

Until you get a local ground electrode out there I would be careful
bonding anything. It is best to drive 2 rods 6 feet or more apart.


Ground rods alone are not a good substitute for the the 4th ground WIRE.

I think you need to run the 4th wire so the safety ground is WIRED.

Even the best ground rod is many ohms

m

On Mon, 10 Jun 2019 06:14:02 -0700 (PDT), wrote:



Until you get a local ground electrode out there I would be careful
bonding anything. It is best to drive 2 rods 6 feet or more apart.


Ground rods alone are not a good substitute for the the 4th ground WIRE.

I think you need to run the 4th wire so the safety ground is WIRED.

Even the best ground rod is many ohms

m

True but the code allowed you to use the neutral for a ground until
the 1996 cycle was adopted and there are plenty of 3 wire feeders,
dryers and ranges out there.
In the case of a second building you always need a ground electrode
and even on those old ranges and dryers, the manufacturer's
instructions suggested a supplemental grounding wire. In those days it
went to a cold water pipe. Now that it is becoming rare to find metal
pipe, that doesn't really work.

On 6/10/2019 8:14 AM, wrote:
Until you get a local ground electrode out there I would be careful
bonding anything. It is best to drive 2 rods 6 feet or more apart.

Ground rods alone are not a good substitute for the the 4th ground WIRE.

I think you need to run the 4th wire so the safety ground is WIRED.

Even the best ground rod is many ohms

m

Â* So the ground rod I drove 8 feet into the ground under the meter is
useless ? I suppose the ground wire on the power pole is useless too ?
What's the point of even grounding the system if the most common means
of grounding is useless ? I'll be taking gfretwell's recommendation to
ground the panel in the shop .

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !

On Sunday, June 9, 2019 at 10:40:23 PM UTC-4, wrote:
On Sun, 9 Jun 2019 20:01:54 -0500, Terry Coombs
wrote:


Â* When is it necessary ? I've just replaced the panel out in the shop
(aluminum buss bars on the old one were giving problems) and I have a 3
wire service run out there . At this time the only place the neutral is
bonded to ground is in the meter box . It has been suggested to me to
bond them in the main panel too ... but that seems redundant to me ,
they're only the thickness of a piece of plywood apart . I have
considered installing a ground rod at the new panel but am concerned
about the potential for ground loop currents .

If you only have 3 wires in the feeder going to the shop you need to
bond the neutral and ground out there too or there is no path for
fault current. You also need a ground electrode out there. Current
code requires a 4 wire feeder and isolating neutral and ground in sub
panels but if the wire was already there when the 1996 code was
adopted the 3 wire feeder is grandfathered in.
Ground loops are not an issue but carrying circuit current in the
grounding conductor is, That is why you do need another ground
electrode. Essentially you are creating another service in the second
building and creating a new ground reference there.
In the electrical biz, you can't have too many ground electrodes but
they all need to be bonded together.

His main question appeared to be whether the neutral and ground need
to be bonded in the MAIN panel if they are already bonded at the meter
which is right next to it?

On Monday, June 10, 2019 at 9:14:09 AM UTC-4, wrote:

Until you get a local ground electrode out there I would be careful
bonding anything. It is best to drive 2 rods 6 feet or more apart.


Ground rods alone are not a good substitute for the the 4th ground WIRE.

I think you need to run the 4th wire so the safety ground is WIRED.

Even the best ground rod is many ohms

m


Even connecting to the ground wire back to the panel is then only
as good as whatever grounds that......

On Sun, 09 Jun 2019 22:45:08 -0400, wrote:

On Sun, 09 Jun 2019 21:37:01 -0400, Clare Snyder
wrote:

On Sun, 9 Jun 2019 20:01:54 -0500, Terry Coombs
wrote:


* When is it necessary ? I've just replaced the panel out in the shop
(aluminum buss bars on the old one were giving problems) and I have a 3
wire service run out there . At this time the only place the neutral is
bonded to ground is in the meter box . It has been suggested to me to
bond them in the main panel too ... but that seems redundant to me ,
they're only the thickness of a piece of plywood apart . I have
considered installing a ground rod at the new panel but am concerned
about the potential for ground loop currents .
by cide the seb has to be "floating" - the neutral and ground bonded
pnly at one point DOWNSTREAM OF THE MAIN DISCONNECT. The main panel
gets "bonded" - nothuing else does - including a connected generator

You float the neutral if you have a 4 wire feeder but if you are still
working with that older 3 wire feeder, you need to reground the
neutral. That was only legal in a second building. In a single
building, all sub panels needed a 4 wire feeder and always have.

Generators will depend on what transfer equipment you are using. If
you switch the neutral, the generator is a separately derived system
and you bond the neutral since the main bonding jumper in the service
disconnect is not in the system anymore.
I was kinda ASS U ME ing that we were talking a 4 wire cable and we
were talking about bonding the neutral WIRE to the ground WIRE.

The only way anyone up here would have a 3 wire feed to an
outbuilding would be if it was origionally set up for a 120 volt panel
- and then one wire would be bare - - - unless it was over 50 years
old (at least). switched neutral transfer would be uncommon, i would
assume. Only REQUIRED for a bonded neutral generator equipped with a
GFI outlet.

On my generator I removed the bond jumper so I can connect it to the
house and made a "bonding plug" that allows me to bond the neutral by
simply putting the bonding plug into one of the 120 volt outlets. The
plug has a jumper from neutral tothe safety ground.

On Mon, 10 Jun 2019 06:14:02 -0700 (PDT), wrote:



Until you get a local ground electrode out there I would be careful
bonding anything. It is best to drive 2 rods 6 feet or more apart.


Ground rods alone are not a good substitute for the the 4th ground WIRE.

I think you need to run the 4th wire so the safety ground is WIRED.

Even the best ground rod is many ohms

m
That would be MY suggestion as well.

On Mon, 10 Jun 2019 09:27:42 -0500, Terry Coombs
wrote:

On 6/10/2019 8:14 AM, wrote:
Until you get a local ground electrode out there I would be careful
bonding anything. It is best to drive 2 rods 6 feet or more apart.

Ground rods alone are not a good substitute for the the 4th ground WIRE.

I think you need to run the 4th wire so the safety ground is WIRED.

Even the best ground rod is many ohms

m

Â* So the ground rod I drove 8 feet into the ground under the meter is
useless ? I suppose the ground wire on the power pole is useless too ?
What's the point of even grounding the system if the most common means
of grounding is useless ? I'll be taking gfretwell's recommendation to
ground the panel in the shop .

It is not useless but it is also not 100% effective. A lot depends on
what kind of soil you have and where the water table is.
My house probably has the best grounding system on my street, 6 rods
in different places, a concrete encased electrode in my addition, the
2400 square foot patio slab is bonded and I have an in ground pool. If
I measure the grounded conductor on my service I have over 2 amps of
current with my main breaker off. I am grounding the whole street I
imagine. I also looked at the pole grounding conductors going up the
road and they vary from 0.5a to almost 3. It is clear ground ain't
"ground".
The good news for me is I have never had any lightning damage since my
surge protection system has a good ground to work with.

On Mon, 10 Jun 2019 09:09:50 -0700 (PDT), trader_4
wrote:

On Sunday, June 9, 2019 at 10:40:23 PM UTC-4, wrote:
On Sun, 9 Jun 2019 20:01:54 -0500, Terry Coombs
wrote:


Â* When is it necessary ? I've just replaced the panel out in the shop
(aluminum buss bars on the old one were giving problems) and I have a 3
wire service run out there . At this time the only place the neutral is
bonded to ground is in the meter box . It has been suggested to me to
bond them in the main panel too ... but that seems redundant to me ,
they're only the thickness of a piece of plywood apart . I have
considered installing a ground rod at the new panel but am concerned
about the potential for ground loop currents .

If you only have 3 wires in the feeder going to the shop you need to
bond the neutral and ground out there too or there is no path for
fault current. You also need a ground electrode out there. Current
code requires a 4 wire feeder and isolating neutral and ground in sub
panels but if the wire was already there when the 1996 code was
adopted the 3 wire feeder is grandfathered in.
Ground loops are not an issue but carrying circuit current in the
grounding conductor is, That is why you do need another ground
electrode. Essentially you are creating another service in the second
building and creating a new ground reference there.
In the electrical biz, you can't have too many ground electrodes but
they all need to be bonded together.

His main question appeared to be whether the neutral and ground need
to be bonded in the MAIN panel if they are already bonded at the meter
which is right next to it?


That is open to debate. A strict reading of the NEC says the PoCo
should not have bonded the neutral in their can but since they do not
have to follow the NEC, the language was tweaked a little (again 96 as
I recall) so it is all "service equipment" and you still rebond the
neutral in the service disconnect enclosure where the code says the
"Main Bonding Jumper" is supposed to be. That is usually just a green
screw on the neutral bus or a strap.
The hitch is that the MBJ "shall remain accessible" and inside the
meter can isn't. Sanity prevailed. Meter cans are usually made so the
can is bonded to the neutral anyway. There is no way to avoid it.

Some inspectors require that there be no metallic paths between the
meter can (a PVC sleeve) and that you only bring 3 wires in. Then we
did not care what they did in the can, the MBJ was clearly in the
service disconnect enclosure.

The grounding electrode conductor can land anywhere from the service
point (usually the mast head on an overhead drop) to the service
disconnect enclosure. That is how they can land it in the meter can.
If you have an underground service lateral, the service point is
usually the transformer connection at the street. Yes you usually own
that wire in the yard. You typically do not own an overhead drop.

On Mon, 10 Jun 2019 13:06:50 -0400, Clare Snyder
wrote:

On Sun, 09 Jun 2019 22:45:08 -0400, wrote:

On Sun, 09 Jun 2019 21:37:01 -0400, Clare Snyder
wrote:

On Sun, 9 Jun 2019 20:01:54 -0500, Terry Coombs
wrote:


Â* When is it necessary ? I've just replaced the panel out in the shop
(aluminum buss bars on the old one were giving problems) and I have a 3
wire service run out there . At this time the only place the neutral is
bonded to ground is in the meter box . It has been suggested to me to
bond them in the main panel too ... but that seems redundant to me ,
they're only the thickness of a piece of plywood apart . I have
considered installing a ground rod at the new panel but am concerned
about the potential for ground loop currents .
by cide the seb has to be "floating" - the neutral and ground bonded
pnly at one point DOWNSTREAM OF THE MAIN DISCONNECT. The main panel
gets "bonded" - nothuing else does - including a connected generator

You float the neutral if you have a 4 wire feeder but if you are still
working with that older 3 wire feeder, you need to reground the
neutral. That was only legal in a second building. In a single
building, all sub panels needed a 4 wire feeder and always have.

Generators will depend on what transfer equipment you are using. If
you switch the neutral, the generator is a separately derived system
and you bond the neutral since the main bonding jumper in the service
disconnect is not in the system anymore.
I was kinda ASS U ME ing that we were talking a 4 wire cable and we
were talking about bonding the neutral WIRE to the ground WIRE.

The only way anyone up here would have a 3 wire feed to an
outbuilding would be if it was origionally set up for a 120 volt panel
- and then one wire would be bare - - - unless it was over 50 years
old (at least).
The code changed here in 1996 and Canada usually mirrored the US code
pretty much. Maybe the war was over earlier up there ;-)


switched neutral transfer would be uncommon, i would
assume. Only REQUIRED for a bonded neutral generator equipped with a
GFI outlet.

Real transfer equipment usually switches the neutral. It is generally
breaker interlock systems that don't. I suppose the installer should
know what he is installing tho. The scary thing is how many licensed
electricians, particularly residential, who do not understand
separately derived systems.

On my generator I removed the bond jumper so I can connect it to the
house and made a "bonding plug" that allows me to bond the neutral by
simply putting the bonding plug into one of the 120 volt outlets. The
plug has a jumper from neutral tothe safety ground.

For most people, it is better to leave the jumper there if it is a
portable generator. The down side of not having it is worse than
having it. As long as the EGC in the connecting cable is the same size
as the circuit conductors, there is really no big issue. You do have a
parallel neutral conductor but babies are not going to die.

On Mon, 10 Jun 2019 13:09:40 -0400, Clare Snyder
wrote:

On Mon, 10 Jun 2019 06:14:02 -0700 (PDT), wrote:



Until you get a local ground electrode out there I would be careful
bonding anything. It is best to drive 2 rods 6 feet or more apart.


Ground rods alone are not a good substitute for the the 4th ground WIRE.

I think you need to run the 4th wire so the safety ground is WIRED.

Even the best ground rod is many ohms

m
That would be MY suggestion as well.


Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.

Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.

the ground connection serves 2 purposes

1) a path for lightning
the ground rod is to provide a path for lightning etc.
this NEEDS to be a path to actual Earth ground because that is where lightning will go.

2) protection from shock due to equipment faults
this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however, when the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground fault. Often a ground rod alone is too high resistance.

#2 is an important safety feature, I would not skimp on this.


So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

You can also add a ground rod there to help for lightning.

If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V.



mark

On Tuesday, June 11, 2019 at 9:32:21 AM UTC-4, wrote:


Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.

the ground connection serves 2 purposes

1) a path for lightning
the ground rod is to provide a path for lightning etc.
this NEEDS to be a path to actual Earth ground because that is where lightning will go.

2) protection from shock due to equipment faults
this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however, when the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground fault. Often a ground rod alone is too high resistance.

#2 is an important safety feature, I would not skimp on this.


So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

You can also add a ground rod there to help for lightning.

If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V.



mark

So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

On second thought, there is a bad fault case here, if that ground/neutral wire should fail OPEN, there will be power on all the grounded stuff in the outbuilding. This is the same problem with 3 wire cords for dryers. I would not do it.

Either add the 4th wire or use the 3 wires for a 120 V feed as hot/neutral/ ground.

mark

On Sunday, June 9, 2019 at 8:00:52 PM UTC-5, Terry Coombs wrote:
Â* When is it necessary ? I've just replaced the panel out in the shop
(aluminum buss bars on the old one were giving problems) and I have a 3
wire service run out there . At this time the only place the neutral is
bonded to ground is in the meter box . It has been suggested to me to
bond them in the main panel too ... but that seems redundant to me ,
they're only the thickness of a piece of plywood apart . I have
considered installing a ground rod at the new panel but am concerned
about the potential for ground loop currents .

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !

And all this assumes that the three wires are NOT in a metal pipe.

On Tue, 11 Jun 2019 06:53:44 -0700 (PDT), Mark
wrote:

On Sunday, June 9, 2019 at 8:00:52 PM UTC-5, Terry Coombs wrote:
* When is it necessary ? I've just replaced the panel out in the shop
(aluminum buss bars on the old one were giving problems) and I have a 3
wire service run out there . At this time the only place the neutral is
bonded to ground is in the meter box . It has been suggested to me to
bond them in the main panel too ... but that seems redundant to me ,
they're only the thickness of a piece of plywood apart . I have
considered installing a ground rod at the new panel but am concerned
about the potential for ground loop currents .

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !

And all this assumes that the three wires are NOT in a metal pipe.
In which case the "metal pipe" - aka conduit - IS the ground - both
contiguous to the panel (hopefully) and "real ground"

On Tuesday, June 11, 2019 at 9:32:21 AM UTC-4, wrote:


Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.

the ground connection serves 2 purposes

1) a path for lightning
the ground rod is to provide a path for lightning etc.
this NEEDS to be a path to actual Earth ground because that is where lightning will go.

2) protection from shock due to equipment faults
this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however, when the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system.

And he has said that they are bonded, at the meter.




This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground fault. Often a ground rod alone is too high resistance.

#2 is an important safety feature, I would not skimp on this.


So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

I didn't see anyone suggesting using ground rods and not bonding that
to the neutral at the second building, it's what code requires.






You can also add a ground rod there to help for lightning.

A ground rod is pretty much not an option and there should have been
at least one there already. With 3 wires, it has to be earthed to
comply with code, and options other than ground rods probably don't
exist, unless that shop building has underground metal water pipes.






If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V.



mark

On Tuesday, June 11, 2019 at 9:43:52 AM UTC-4, wrote:
On Tuesday, June 11, 2019 at 9:32:21 AM UTC-4, wrote:


Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.

the ground connection serves 2 purposes

1) a path for lightning
the ground rod is to provide a path for lightning etc.
this NEEDS to be a path to actual Earth ground because that is where lightning will go.

2) protection from shock due to equipment faults
this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however, when the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground fault. Often a ground rod alone is too high resistance.

#2 is an important safety feature, I would not skimp on this.


So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

You can also add a ground rod there to help for lightning.

If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V.



mark

So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

On second thought, there is a bad fault case here, if that ground/neutral wire should fail OPEN, there will be power on all the grounded stuff in the outbuilding. This is the same problem with 3 wire cords for dryers.

Dryers don't have an earth ground, ie ground rods, his subpanel would/should,
so it's not the same problem. If that subpanel in the shop already had
a ground rod, I would think most inspectors would allow the panel replacement
using ground rods.



I would not do it.

Either add the 4th wire or use the 3 wires for a 120 V feed as hot/neutral/ ground.

mark

That doesn't sound very attractive for a shop, loss of 240V and cutting
the available 120V power in half.

On 6/11/2019 8:32 AM, wrote:


Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.
the ground connection serves 2 purposes

1) a path for lightning
the ground rod is to provide a path for lightning etc.
this NEEDS to be a path to actual Earth ground because that is where lightning will go.

2) protection from shock due to equipment faults
this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however, when the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground fault. Often a ground rod alone is too high resistance.

#2 is an important safety feature, I would not skimp on this.


So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

You can also add a ground rod there to help for lightning.

If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V.



mark


Â* Done is done , I have bonded the ground/neutral in the sub panel and
added a ground rod out in the shop . Doing without 240V is unacceptable
, I have 2 welders and an air compressor that all need 240V . And plans
are to install a 240V 3 phase motor with a VFD on the mill in the future
.. Lightning is unlikely down in The Holler , but still possible . This
is a "hobby" shop , but is very well equipped - pretty much a full
machine and welding shop .

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !

On Tuesday, June 11, 2019 at 12:47:52 PM UTC-4, Terry Coombs wrote:
On 6/11/2019 8:32 AM, wrote:


Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.
the ground connection serves 2 purposes

1) a path for lightning
the ground rod is to provide a path for lightning etc.
this NEEDS to be a path to actual Earth ground because that is where lightning will go.

2) protection from shock due to equipment faults
this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however, when the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground fault. Often a ground rod alone is too high resistance.

#2 is an important safety feature, I would not skimp on this.


So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

You can also add a ground rod there to help for lightning.

If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V.



mark


Â* Done is done , I have bonded the ground/neutral in the sub panel and
added a ground rod out in the shop . Doing without 240V is unacceptable
, I have 2 welders and an air compressor that all need 240V . And plans
are to install a 240V 3 phase motor with a VFD on the mill in the future
. Lightning is unlikely down in The Holler , but still possible . This
is a "hobby" shop , but is very well equipped - pretty much a full
machine and welding shop .

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !

That's what I would have done too, except probably adding a second ground
rod. IDK how you're going to install 3 phase eqpt though, without redoing
what you just did and a whole new service, for that matter?

On Tue, 11 Jun 2019 06:32:15 -0700 (PDT), wrote:




Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.

the ground connection serves 2 purposes

1) a path for lightning
the ground rod is to provide a path for lightning etc.
this NEEDS to be a path to actual Earth ground because that is where lightning will go.

2) protection from shock due to equipment faults
this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however, when the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground fault. Often a ground rod alone is too high resistance.

#2 is an important safety feature, I would not skimp on this.


So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

You can also add a ground rod there to help for lightning.

If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V.



mark

With a 3 wire feeder you are REQUIRED to bond the EGC (ground) to the
neutral.
The earth is NEVER a fault path.
You are also required to provide a ground electrode system.
If you drive a rod and if you can't demonstrate that it has 25 ohms
to ground, you need the second rod more than 6' from the first one.
That has been code since Thomas Edison was around.

On Tue, 11 Jun 2019 06:43:47 -0700 (PDT), wrote:

On Tuesday, June 11, 2019 at 9:32:21 AM UTC-4, wrote:


Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.

the ground connection serves 2 purposes

1) a path for lightning
the ground rod is to provide a path for lightning etc.
this NEEDS to be a path to actual Earth ground because that is where lightning will go.

2) protection from shock due to equipment faults
this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however, when the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground fault. Often a ground rod alone is too high resistance.

#2 is an important safety feature, I would not skimp on this.


So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

You can also add a ground rod there to help for lightning.

If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V.



mark

So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

On second thought, there is a bad fault case here, if that ground/neutral wire should fail OPEN, there will be power on all the grounded stuff in the outbuilding. This is the same problem with 3 wire cords for dryers. I would not do it.

Either add the 4th wire or use the 3 wires for a 120 V feed as hot/neutral/ ground.

mark


Whatever makes you feel safer but there are 10s of millions of
circuits and feeders running like that safely for the last 100 years
or so. The main justification in the code change was simply
consistency in the code, not any particular tombstone count.
You can look at the 96 ROP if you like.
Phil Simmonds wrote the proposal and his words were "the war is over"
We don't need to save copper anymore, in reference to ranges and
dryers.
(although the 3 wire feeder was around long before WWII)

On Tue, 11 Jun 2019 06:53:44 -0700 (PDT), Mark
wrote:

On Sunday, June 9, 2019 at 8:00:52 PM UTC-5, Terry Coombs wrote:
Â* When is it necessary ? I've just replaced the panel out in the shop
(aluminum buss bars on the old one were giving problems) and I have a 3
wire service run out there . At this time the only place the neutral is
bonded to ground is in the meter box . It has been suggested to me to
bond them in the main panel too ... but that seems redundant to me ,
they're only the thickness of a piece of plywood apart . I have
considered installing a ground rod at the new panel but am concerned
about the potential for ground loop currents .

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !

And all this assumes that the three wires are NOT in a metal pipe.

That would be an EGC if it was galvanized rigid iron pipe (the
threaded stuff) but if it is just EMT, in a few years that might be
red dust underground. I haven't seen metal raceways in the ground here
unless they were poured solid in a concrete duct bank and even then
the state required a green wire ground.

On Tue, 11 Jun 2019 09:39:14 -0700 (PDT), trader_4
wrote:

On Tuesday, June 11, 2019 at 9:43:52 AM UTC-4, wrote:
On Tuesday, June 11, 2019 at 9:32:21 AM UTC-4, wrote:


Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.

the ground connection serves 2 purposes

1) a path for lightning
the ground rod is to provide a path for lightning etc.
this NEEDS to be a path to actual Earth ground because that is where lightning will go.

2) protection from shock due to equipment faults
this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however, when the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground fault. Often a ground rod alone is too high resistance.

#2 is an important safety feature, I would not skimp on this.


So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

You can also add a ground rod there to help for lightning.

If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V.



mark

So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

On second thought, there is a bad fault case here, if that ground/neutral wire should fail OPEN, there will be power on all the grounded stuff in the outbuilding. This is the same problem with 3 wire cords for dryers.

Dryers don't have an earth ground, ie ground rods, his subpanel would/should,
so it's not the same problem. If that subpanel in the shop already had
a ground rod, I would think most inspectors would allow the panel replacement
using ground rods.


Two ground rods unless you can show me a grounding electrode survey by
an engineering firm. (Just drive 2 rods)

On Tue, 11 Jun 2019 11:48:12 -0500, Terry Coombs
wrote:

On 6/11/2019 8:32 AM, wrote:


Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.
the ground connection serves 2 purposes

1) a path for lightning
the ground rod is to provide a path for lightning etc.
this NEEDS to be a path to actual Earth ground because that is where lightning will go.

2) protection from shock due to equipment faults
this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however, when
the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground fault.
Often a ground rod alone is too high resistance.

#2 is an important safety feature, I would not skimp on this.


So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

You can also add a ground rod there to help for lightning.

If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V.



mark


Â* Done is done , I have bonded the ground/neutral in the sub panel and
added a ground rod out in the shop . Doing without 240V is unacceptable
, I have 2 welders and an air compressor that all need 240V . And plans
are to install a 240V 3 phase motor with a VFD on the mill in the future
. Lightning is unlikely down in The Holler , but still possible . This
is a "hobby" shop , but is very well equipped - pretty much a full
machine and welding shop .

Rock on dude ;-)

On 6/11/2019 12:43 PM, wrote:
On Tue, 11 Jun 2019 11:48:12 -0500, Terry Coombs
wrote:

On 6/11/2019 8:32 AM, wrote:

Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.
the ground connection serves 2 purposes

1) a path for lightning
the ground rod is to provide a path for lightning etc.
this NEEDS to be a path to actual Earth ground because that is where lightning will go.

2) protection from shock due to equipment faults
this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however, when
the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground fault.
Often a ground rod alone is too high resistance.
#2 is an important safety feature, I would not skimp on this.


So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

You can also add a ground rod there to help for lightning.

If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V.



mark

Â* Done is done , I have bonded the ground/neutral in the sub panel and
added a ground rod out in the shop . Doing without 240V is unacceptable
, I have 2 welders and an air compressor that all need 240V . And plans
are to install a 240V 3 phase motor with a VFD on the mill in the future
. Lightning is unlikely down in The Holler , but still possible . This
is a "hobby" shop , but is very well equipped - pretty much a full
machine and welding shop .
Rock on dude ;-)
Â* Well ,this afternoon it's a country mix on YouTube ...

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !

On Tue, 11 Jun 2019 10:21:46 -0700 (PDT), trader_4
wrote:

On Tuesday, June 11, 2019 at 12:47:52 PM UTC-4, Terry Coombs wrote:
On 6/11/2019 8:32 AM, wrote:


Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.
the ground connection serves 2 purposes

1) a path for lightning
the ground rod is to provide a path for lightning etc.
this NEEDS to be a path to actual Earth ground because that is where lightning will go.

2) protection from shock due to equipment faults
this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however,
when the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground fault.
Often a ground rod alone is too high resistance.

#2 is an important safety feature, I would not skimp on this.


So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

You can also add a ground rod there to help for lightning.

If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V.



mark


Â* Done is done , I have bonded the ground/neutral in the sub panel and
added a ground rod out in the shop . Doing without 240V is unacceptable
, I have 2 welders and an air compressor that all need 240V . And plans
are to install a 240V 3 phase motor with a VFD on the mill in the future
. Lightning is unlikely down in The Holler , but still possible . This
is a "hobby" shop , but is very well equipped - pretty much a full
machine and welding shop .

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !

That's what I would have done too, except probably adding a second ground
rod. IDK how you're going to install 3 phase eqpt though, without redoing
what you just did and a whole new service, for that matter?

You can get a VFD that is single phase in and 3 phase out

On Tuesday, June 11, 2019 at 5:05:03 PM UTC-4, wrote:
On Tue, 11 Jun 2019 10:21:46 -0700 (PDT), trader_4
wrote:

On Tuesday, June 11, 2019 at 12:47:52 PM UTC-4, Terry Coombs wrote:
On 6/11/2019 8:32 AM, wrote:


Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.
the ground connection serves 2 purposes

1) a path for lightning
the ground rod is to provide a path for lightning etc.
this NEEDS to be a path to actual Earth ground because that is where lightning will go.

2) protection from shock due to equipment faults
this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however,
when the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance.. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground fault.
Often a ground rod alone is too high resistance.

#2 is an important safety feature, I would not skimp on this.


So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

You can also add a ground rod there to help for lightning.

If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V.



mark


Â* Done is done , I have bonded the ground/neutral in the sub panel and
added a ground rod out in the shop . Doing without 240V is unacceptable
, I have 2 welders and an air compressor that all need 240V . And plans
are to install a 240V 3 phase motor with a VFD on the mill in the future
. Lightning is unlikely down in The Holler , but still possible . This
is a "hobby" shop , but is very well equipped - pretty much a full
machine and welding shop .

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !

That's what I would have done too, except probably adding a second ground
rod. IDK how you're going to install 3 phase eqpt though, without redoing
what you just did and a whole new service, for that matter?

You can get a VFD that is single phase in and 3 phase out

I see, well that solves that.

So here's another puzzling question. In that thread about solar panels
that has now run amok, Danny brought up the issue of preventing backfeeding
into the grid. AFAIK, that's built into the inverters, but how do they
do it? It would seem like the chicken and the egg problem. You need to
detect the grid power going off, but you are connected directly to it and
also powering it. So, how do they detect it? Obviously before connecting
they must first monitor the voltage, freq and phase and sync to it, but
once you connect, how do you then tell the other grid sources are gone?
I guess you could look for voltage drop, since with the grid down
you'd expect 99.9% there will be big voltage decrease. But is that
sufficient? And what do they really do inside those inverters?

Hypothetically, suppose there are 6 houses on a utility line that
have solar and that segment is connected to the whole distribution
system. The sun is shining, those houses are using significantly
less than the panels put out. I cut the line to the rest of the grid,
leaving just those 6 connected. What happens? Is the "grid" down?
How do those inverters detect it? Do they? What happens?

On 6/11/2019 4:05 PM, wrote:
On Tue, 11 Jun 2019 10:21:46 -0700 (PDT), trader_4
wrote:

On Tuesday, June 11, 2019 at 12:47:52 PM UTC-4, Terry Coombs wrote:
On 6/11/2019 8:32 AM, wrote:

Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.
the ground connection serves 2 purposes

1) a path for lightning
the ground rod is to provide a path for lightning etc.
this NEEDS to be a path to actual Earth ground because that is where lightning will go.

2) protection from shock due to equipment faults
this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however,
when the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground fault.
Often a ground rod alone is too high resistance.
#2 is an important safety feature, I would not skimp on this.


So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

You can also add a ground rod there to help for lightning.

If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V.



mark

Â* Done is done , I have bonded the ground/neutral in the sub panel and
added a ground rod out in the shop . Doing without 240V is unacceptable
, I have 2 welders and an air compressor that all need 240V . And plans
are to install a 240V 3 phase motor with a VFD on the mill in the future
. Lightning is unlikely down in The Holler , but still possible . This
is a "hobby" shop , but is very well equipped - pretty much a full
machine and welding shop .

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !
That's what I would have done too, except probably adding a second ground
rod. IDK how you're going to install 3 phase eqpt though, without redoing
what you just did and a whole new service, for that matter?
You can get a VFD that is single phase in and 3 phase out
Â* Oops , I missed t-4's post ... yes , single in and 3 out , 240 is
just more efficient than converting 120 . I'm considering bonding the
structure frame to the ground too - this began life as a 12' x 20' metal
carport . All metal structure with IIRC 8 - 5/8" by 2 foot long spikes
driven into the ground and concrete floor . All it'd take is one lag
screw thru the side of the box and one 2x4 into the vertical tube .

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !

On 6/11/2019 12:37 PM, wrote:
....

Whatever makes you feel safer but there are 10s of millions of
circuits and feeders running like that safely for the last 100 years
or so. The main justification in the code change was simply
consistency in the code, not any particular tombstone count.
You can look at the 96 ROP if you like.
Phil Simmonds wrote the proposal and his words were "the war is over"
We don't need to save copper anymore, in reference to ranges and
dryers.
(although the 3 wire feeder was around long before WWII)

Actually one WW prior to that, even...altho many houses then didn't yet
have 220 V service, three-wire was what was used if did...we didn't get
REA service until post WWII (1948 when they finally reached us) so
everything on the place here dates from then altho the house was wired
when built in 1916 for the Delco windcharger system, it was just
two-wire K&T for the 32 VDC. Still have all the old mother-of-pearl
inlaid pushbutton light switches that are classic in looks but not up to
120 VAC, sadly.

--

On Tue, 11 Jun 2019 14:20:47 -0700 (PDT), trader_4
wrote:

On Tuesday, June 11, 2019 at 5:05:03 PM UTC-4, wrote:
On Tue, 11 Jun 2019 10:21:46 -0700 (PDT), trader_4
wrote:

On Tuesday, June 11, 2019 at 12:47:52 PM UTC-4, Terry Coombs wrote:
On 6/11/2019 8:32 AM, wrote:


Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.
the ground connection serves 2 purposes

1) a path for lightning
the ground rod is to provide a path for lightning etc.
this NEEDS to be a path to actual Earth ground because that is where lightning will go.

2) protection from shock due to equipment faults
this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however,
when the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground
fault.
Often a ground rod alone is too high resistance.

#2 is an important safety feature, I would not skimp on this.


So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

You can also add a ground rod there to help for lightning.

If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V.



mark


Â* Done is done , I have bonded the ground/neutral in the sub panel and
added a ground rod out in the shop . Doing without 240V is unacceptable
, I have 2 welders and an air compressor that all need 240V . And plans
are to install a 240V 3 phase motor with a VFD on the mill in the future
. Lightning is unlikely down in The Holler , but still possible . This
is a "hobby" shop , but is very well equipped - pretty much a full
machine and welding shop .

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !

That's what I would have done too, except probably adding a second ground
rod. IDK how you're going to install 3 phase eqpt though, without redoing
what you just did and a whole new service, for that matter?

You can get a VFD that is single phase in and 3 phase out

I see, well that solves that.

So here's another puzzling question. In that thread about solar panels
that has now run amok, Danny brought up the issue of preventing backfeeding
into the grid. AFAIK, that's built into the inverters, but how do they
do it? It would seem like the chicken and the egg problem. You need to
detect the grid power going off, but you are connected directly to it and
also powering it. So, how do they detect it? Obviously before connecting
they must first monitor the voltage, freq and phase and sync to it, but
once you connect, how do you then tell the other grid sources are gone?
I guess you could look for voltage drop, since with the grid down
you'd expect 99.9% there will be big voltage decrease. But is that
sufficient? And what do they really do inside those inverters?

Hypothetically, suppose there are 6 houses on a utility line that
have solar and that segment is connected to the whole distribution
system. The sun is shining, those houses are using significantly
less than the panels put out. I cut the line to the rest of the grid,
leaving just those 6 connected. What happens? Is the "grid" down?
How do those inverters detect it? Do they? What happens?

We got a pitch on these things a while ago. Basically a grid tie
inverter is clocked from the grid. No grid, no output. They run at a
voltage that can be potentially slightly higher than the grid so if
there is any power left over, it flows backward into the grid. A smart
meter will see that and meter based on your local tariff agreement.
The old style would just run backward if net flow was out instead of
in. If you netted more use than you fed back in, no harm, just a
lower bill. If you showed a negative bill I guess you would be talking
to the PoCo.
That is how people used to steal power, plug the meter in upside down
it runs backward so there is a chance you would be starting in the
fraud department if they did not know about your solar.
The "plug in" collectors plug in just like your toaster and will boost
the power on that side of your service. These things are usually too
small to ever feed back into the grid if you have anything running at
all.

On Tuesday, June 11, 2019 at 7:46:48 PM UTC-4, wrote:
On Tue, 11 Jun 2019 14:20:47 -0700 (PDT), trader_4
wrote:

On Tuesday, June 11, 2019 at 5:05:03 PM UTC-4, wrote:
On Tue, 11 Jun 2019 10:21:46 -0700 (PDT), trader_4
wrote:

On Tuesday, June 11, 2019 at 12:47:52 PM UTC-4, Terry Coombs wrote:
On 6/11/2019 8:32 AM, wrote:


Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.

On Tue, 11 Jun 2019 16:55:43 -0700 (PDT), trader_4
wrote:

On Tuesday, June 11, 2019 at 7:46:48 PM UTC-4, wrote:
On Tue, 11 Jun 2019 14:20:47 -0700 (PDT), trader_4
wrote:

On Tuesday, June 11, 2019 at 5:05:03 PM UTC-4, wrote:
On Tue, 11 Jun 2019 10:21:46 -0700 (PDT), trader_4
wrote:

On Tuesday, June 11, 2019 at 12:47:52 PM UTC-4, Terry Coombs wrote:
On 6/11/2019 8:32 AM, wrote:


Why is the ground rod at the service any better than the one at the
shop? I agree 4 is better than 2 but they are already bonded together
via the neutral in a 3 wire feeder. I doubt he wants to dig up the
yard. This was done this way for 90 years and we didn't pile up a lot
of bodies. The code change was mostly just to make the language
consistent with the rest of the code. Same with ranges and dryers. The
grandfather clause is still there for things done pre 96 adoption.
It does mean you have to be more careful with your bonding and
grounding tho.
the ground connection serves 2 purposes

1) a path for lightning
the ground rod is to provide a path for lightning etc.
this NEEDS to be a path to actual Earth ground because that is where lightning will go.

2) protection from shock due to equipment faults
this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded
however,
when the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground
fault.
Often a ground rod alone is too high resistance.

#2 is an important safety feature, I would not skimp on this.


So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone.

You can also add a ground rod there to help for lightning.

If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V.



mark


Â* Done is done , I have bonded the ground/neutral in the sub panel and
added a ground rod out in the shop . Doing without 240V is unacceptable
, I have 2 welders and an air compressor that all need 240V . And plans
are to install a 240V 3 phase motor with a VFD on the mill in the future
. Lightning is unlikely down in The Holler , but still possible . This
is a "hobby" shop , but is very well equipped - pretty much a full
machine and welding shop .

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !

That's what I would have done too, except probably adding a second ground
rod. IDK how you're going to install 3 phase eqpt though, without redoing
what you just did and a whole new service, for that matter?

You can get a VFD that is single phase in and 3 phase out

I see, well that solves that.

So here's another puzzling question. In that thread about solar panels
that has now run amok, Danny brought up the issue of preventing backfeeding
into the grid. AFAIK, that's built into the inverters, but how do they
do it? It would seem like the chicken and the egg problem. You need to
detect the grid power going off, but you are connected directly to it and
also powering it. So, how do they detect it? Obviously before connecting
they must first monitor the voltage, freq and phase and sync to it, but
once you connect, how do you then tell the other grid sources are gone?
I guess you could look for voltage drop, since with the grid down
you'd expect 99.9% there will be big voltage decrease. But is that
sufficient? And what do they really do inside those inverters?

Hypothetically, suppose there are 6 houses on a utility line that
have solar and that segment is connected to the whole distribution
system. The sun is shining, those houses are using significantly
less than the panels put out. I cut the line to the rest of the grid,
leaving just those 6 connected. What happens? Is the "grid" down?
How do those inverters detect it? Do they? What happens?

We got a pitch on these things a while ago. Basically a grid tie
inverter is clocked from the grid. No grid, no output.

But the question remains, the inverter is part of the grid, the inverters
along the block are part of the grid, in addition to some generators
somewhere. So, how does it know that the "grid" is down?

Hypothetically, suppose there are 6 houses on a utility line that
have solar and that segment is connected to the whole distribution
system. The sun is shining, those houses are using significantly
less than the panels put out. I cut the line to the rest of the grid,
leaving just those 6 connected. What happens? Is the "grid" down?
How do those inverters detect it? Do they? What happens?

That is an interesting question but theoretically each grid tied
inverter would lose clocking and shut down.
I have posed this question to everyone I have talked to without an
answer. What happens if you disconnect from the grid, drop all of
your loads and connect a battery powered inverter. Will that clock
your grid tie and allow you to add loads until you overwhelm it?

They run at a
voltage that can be potentially slightly higher than the grid so if
there is any power left over, it flows backward into the grid. A smart
meter will see that and meter based on your local tariff agreement.
The old style would just run backward if net flow was out instead of
in. If you netted more use than you fed back in, no harm, just a
lower bill. If you showed a negative bill I guess you would be talking
to the PoCo.
That is how people used to steal power, plug the meter in upside down
it runs backward so there is a chance you would be starting in the
fraud department if they did not know about your solar.
The "plug in" collectors plug in just like your toaster and will boost
the power on that side of your service. These things are usually too
small to ever feed back into the grid if you have anything running at
all.

But from everything I see, a 10KW home solar system behaves exactly
like the plug in ones and needs to detect when to disconnect.

That is the way I understand it. Each inverter should detect loss of
grid and shut down. It would be interesting if you had something else
feeding the grid like your generator idea that the plan might fail. I
also doubt there is enough power going into the grid to sustain it if
you are not getting utility power, even if you have a lot of people
with a black roof.
This might work if you had one guy on a street full of solar power
systems with a generator back feeding the street to tickle everyone's
inverter, all residents being frugal and a line cut isolating that
street from the rest of the grid.
It would work until sundown anyway ;-)

Â* Done is done , I have bonded the ground/neutral in the sub panel and
added a ground rod out in the shop .

snip...


I agree using the 3 wire system and bonding the neutral and ground is the most practical solution. But be aware, if that third ground/neutral wire should fail open, there will be a dangerous condition in the outbuilding. Everything that was ground, can become energized.



mark