Hello, Im new to the site and was reading the post below about a 400 amp service. Having only installed a 200 amp panel myself I was wondering how you would ground a 400 amp service? If you had 2-200 amp panels could you run 1-#6 wire from 1 panel to a ground rod, and then a #6 wire between the 2 panels? Plus for the cold water ground could you run a wire sized from table 250.66 connecting 1 panel to the cold water pipe and a second wire between the 2 panels? Thank-you.
400 amp service
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Re: 400 amp service
Assuming that you have no separate disconnect, that is, the two 200A panels have main breakers and are your grouped Service Equipment, then you can do as follows:
The neutrals from the meterbase to each panel, if sized 1/0 or larger, are a combination grounded/grounding conductor. You can run your grounding electrode conductors from either of the panels, both of the panels, the meterbase, or the service conduits below the weatherhead.
On mine, I ran a #2 (although #6 is the minimum required) from one panel to two ground rods. I ran a 1/0 from the second panel to the water pipe.
Running a wire between the panels parallels the neutral which is not desireable. I have metal conduits which also create a parallel path, but you have no choice in this case because they must all be bonded.
Assuming that you have no separate disconnect, that is, the two 200A panels have main breakers and are your grouped Service Equipment, then you can do as follows:
The neutrals from the meterbase to each panel, if sized 1/0 or larger, are a combination grounded/grounding conductor. You can run your grounding electrode conductors from either of the panels, both of the panels, the meterbase, or the service conduits below the weatherhead.
On mine, I ran a #2 (although #6 is the minimum required) from one panel to two ground rods. I ran a 1/0 from the second panel to the water pipe.
Running a wire between the panels parallels the neutral which is not desireable. I have metal conduits which also create a parallel path, but you have no choice in this case because they must all be bonded.
A
a.wayne3@verizon.net
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Re: 400 amp service
some areas here require you to size your ground to the largest possible incoming feeder that might be installed is it 250.66 ? 1/0 cu not sure right now but if wrong I`ll be corrected.This is off the top of my head.
some areas here require you to size your ground to the largest possible incoming feeder that might be installed is it 250.66 ? 1/0 cu not sure right now but if wrong I`ll be corrected.This is off the top of my head.
Re: 400 amp service
suemarkp,
From your description of how you did your grounding electrode conections, it seems that you did not bond the ground rods to the water pipe? This would be a violation of 250.50 and 250.53(D)(2). If I am understanding correctly, I would not have passed it.
suemarkp,
From your description of how you did your grounding electrode conections, it seems that you did not bond the ground rods to the water pipe? This would be a violation of 250.50 and 250.53(D)(2). If I am understanding correctly, I would not have passed it.
Re: 400 amp service
Since each of these panels is service equipment, each has a "grounded service conductor" and also has the grounded/grounding bus bonded to the service enclosure. Per 250.53(D)(2), you can bond at any of these locations: "The supplemental electrode shall be permitted to be bonded to the grounding electrode conductor, the grounded service-entrance conductor, the nonflexible grounded service raceway, or any grounded service enclosure."
Since each of these panels is service equipment, each has a "grounded service conductor" and also has the grounded/grounding bus bonded to the service enclosure. Per 250.53(D)(2), you can bond at any of these locations: "The supplemental electrode shall be permitted to be bonded to the grounding electrode conductor, the grounded service-entrance conductor, the nonflexible grounded service raceway, or any grounded service enclosure."
Re: 400 amp service
For the sake of discussion, lets call the panel where the water line is bonded panel A, The grounded conductor supplying that panel GCA, the panel where the ground rods are bonded panel B, and the grounded conductor supplying that panel GCB. There will be a voltage difference between the grounding/neutral bars in the panels. How much depends upon the length of GCA, the length of GCB, and the current flowing through those conductors at any particular time.
I believe the reason for the requirement in 250.50 that all grounding electrodes be bonded together, is to prevent differences of potential within the grounding system. By bonding the water pipe and the grounding rods to different enclosures, you have not bonded them together unless you count the current carrying GCA and GCB as bonding jumpers. There will be a voltage difference between the grounding electrodes. More importantly, suppose the laundry circuit comes off of panel B. The washing machine enclusure will be at the voltage of the panel B grounding bus, while the water faucet next to it will be at the voltage of the panel A bus. A person touching both will become a conductor between the two busses. How much of a problem is this? It all depends. Take a look at this. This would be true of the water line and any appliance supplied from panel B.
When 250.53(D)(2) allows the supplemental electrode to be bonded to "any grounded service enclosure", I believe it presupposes the water line will be bonded to the same enclosure, or if not, that the requirements of 250.50 will be met in some way.
For the sake of discussion, lets call the panel where the water line is bonded panel A, The grounded conductor supplying that panel GCA, the panel where the ground rods are bonded panel B, and the grounded conductor supplying that panel GCB. There will be a voltage difference between the grounding/neutral bars in the panels. How much depends upon the length of GCA, the length of GCB, and the current flowing through those conductors at any particular time.
I believe the reason for the requirement in 250.50 that all grounding electrodes be bonded together, is to prevent differences of potential within the grounding system. By bonding the water pipe and the grounding rods to different enclosures, you have not bonded them together unless you count the current carrying GCA and GCB as bonding jumpers. There will be a voltage difference between the grounding electrodes. More importantly, suppose the laundry circuit comes off of panel B. The washing machine enclusure will be at the voltage of the panel B grounding bus, while the water faucet next to it will be at the voltage of the panel A bus. A person touching both will become a conductor between the two busses. How much of a problem is this? It all depends. Take a look at this. This would be true of the water line and any appliance supplied from panel B.
When 250.53(D)(2) allows the supplemental electrode to be bonded to "any grounded service enclosure", I believe it presupposes the water line will be bonded to the same enclosure, or if not, that the requirements of 250.50 will be met in some way.
Re: 400 amp service
While I agree with what you say, I don't believe it to be illegal (hence the words ANY service entrance enclosure). You can carry this argument to the extreme and worry about the voltage drop between two adjacent bus holes or placing one ground on the "nuetral" bar and one on the (bonded) "grounding" bar. How much voltage drop are you getting through that main bonding jumper??? This voltage drop issue is also independent of the separate ground electrode bonding. This "problem" would still exist if all ground electrodes were in panel A and a metal appliance is fed from panel B.
The voltage drop on my 4 feet of 3/0 copper will be nearly 0. Even if it was 2V or 5V, this is not enough to shock you. I believe the code writers accept that the voltage drop between grouped Service Equipment is close enough to zero that this isn't an issue.
I wanted to run all grounds to a common bar, as that is the best design, but it was more difficult and required 2 sharp bends to use the same panel for a common ground. If I didn't have to use 1/0, then I may have been able to run it to a common grounding bus.
[ October 02, 2004, 04:12 AM: Message edited by: suemarkp ]
While I agree with what you say, I don't believe it to be illegal (hence the words ANY service entrance enclosure). You can carry this argument to the extreme and worry about the voltage drop between two adjacent bus holes or placing one ground on the "nuetral" bar and one on the (bonded) "grounding" bar. How much voltage drop are you getting through that main bonding jumper??? This voltage drop issue is also independent of the separate ground electrode bonding. This "problem" would still exist if all ground electrodes were in panel A and a metal appliance is fed from panel B.
The voltage drop on my 4 feet of 3/0 copper will be nearly 0. Even if it was 2V or 5V, this is not enough to shock you. I believe the code writers accept that the voltage drop between grouped Service Equipment is close enough to zero that this isn't an issue.
I wanted to run all grounds to a common bar, as that is the best design, but it was more difficult and required 2 sharp bends to use the same panel for a common ground. If I didn't have to use 1/0, then I may have been able to run it to a common grounding bus.
[ October 02, 2004, 04:12 AM: Message edited by: suemarkp ]
A
a.wayne3@verizon.net
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Re: 400 amp service
I have built all to many 400amp residential services here.Each one was done the same,320/400 meter base back to backed or split using disconnects.1/0 cu from the meter base to what ever the local requirement was either uffer,grnd rods and copper where present.Do this and no further grounding was required.Two years ago we did a condo complex 12 unit slabbed 2 seperate 6 meter base assemblies fed from main breakers,water was CU.as I interpeted the code it was permissable to ground each main from the nearest Cu pipe which in this case was the incoming cold water to back to back units,1 main 1 unit 2 mains 2 units since the units were seperately water metered and had PVC to CU transition from each unit to the meter I used #4 from the other 10 MLO panels to the Cu in the individual units.
I have built all to many 400amp residential services here.Each one was done the same,320/400 meter base back to backed or split using disconnects.1/0 cu from the meter base to what ever the local requirement was either uffer,grnd rods and copper where present.Do this and no further grounding was required.Two years ago we did a condo complex 12 unit slabbed 2 seperate 6 meter base assemblies fed from main breakers,water was CU.as I interpeted the code it was permissable to ground each main from the nearest Cu pipe which in this case was the incoming cold water to back to back units,1 main 1 unit 2 mains 2 units since the units were seperately water metered and had PVC to CU transition from each unit to the meter I used #4 from the other 10 MLO panels to the Cu in the individual units.
stew
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Re: 400 amp service
Just completed a 600 amp service with 3 200 disc and 1 225 dis grouped. Used the green bonding screw in each panel, installed a bond of #4 cu from the ct can to one of the disc,a #4 from the first disc connected in lay lugs at eaqch of the others and then oout to the ground rods. Meets all requirements and passed very nicely
Just completed a 600 amp service with 3 200 disc and 1 225 dis grouped. Used the green bonding screw in each panel, installed a bond of #4 cu from the ct can to one of the disc,a #4 from the first disc connected in lay lugs at eaqch of the others and then oout to the ground rods. Meets all requirements and passed very nicely
Re: 400 amp service
I'm sure it did. Though the question to answer is was all that #4 wire required? What you did is explicitly permitted, even if you use split bolt stubs off the long #4 to get to each panel.
Is the neutral bonded to the CT can chassis? If so, I would think you could have just run a #6 from any one of those enclosures to the ground rods and been done.
What size water pipe bonding wire did you run and where did you place it?
I'm sure it did. Though the question to answer is was all that #4 wire required? What you did is explicitly permitted, even if you use split bolt stubs off the long #4 to get to each panel.
Is the neutral bonded to the CT can chassis? If so, I would think you could have just run a #6 from any one of those enclosures to the ground rods and been done.
What size water pipe bonding wire did you run and where did you place it?
A
a.wayne3@verizon.net
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Re: 400 amp service
Not all POCO`S require a 600 amp service to be a CT set up,a couple of years age we did 4 homes in a cul de sac that were from 10,000 to 15,000 sq ft load calcs brought them into 600 range .No CT`S a K based meter can triple lugged to 200 amp MBR panels.Simple set up.
Not all POCO`S require a 600 amp service to be a CT set up,a couple of years age we did 4 homes in a cul de sac that were from 10,000 to 15,000 sq ft load calcs brought them into 600 range .No CT`S a K based meter can triple lugged to 200 amp MBR panels.Simple set up.
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