I am replacing an existing service with a new one. 3phase 4wire 1200A 120/208Volts. There will be 4 MAIN DISCONNECT Switches. I know I have to ground & bond the largest switch. For the additional 3 MAIN switches do I only bond the neutral to the enclosure or do I need something else? Any help is appreciated.
Bonding -Grounding the Neutral
- Thread starter kiss
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charlie
Senior Member
- Location
- Indianapolis
Re: Bonding -Grounding the Neutral
250.24(B) Grounded Conductor Brought to Service Equipment. Where an ac system operating at less than 1000 volts is grounded at any point, the grounded conductor(s) (neutral) shall be run to each service disconnecting means and shall be bonded to each disconnecting means enclosure. The grounded conductor(s) shall be installed in accordance with 250.24(B)(1) through (B)(3).
In other words, you don't just ground and bond the largest service but you ground and bond all the services.
250.24(B) Grounded Conductor Brought to Service Equipment. Where an ac system operating at less than 1000 volts is grounded at any point, the grounded conductor(s) (neutral) shall be run to each service disconnecting means and shall be bonded to each disconnecting means enclosure. The grounded conductor(s) shall be installed in accordance with 250.24(B)(1) through (B)(3).
In other words, you don't just ground and bond the largest service but you ground and bond all the services.
pierre
Senior Member
- Location
- Westchester County, New York
Re: Bonding -Grounding the Neutral
Kiss
The method you are explaining is how they use to do it in NYC for a 110 years. Now they are following the NEC and they are as confused as you are.
Pierre
Kiss
The method you are explaining is how they use to do it in NYC for a 110 years. Now they are following the NEC and they are as confused as you are.
Pierre
- Location
- Illinois
- Occupation
- retired electrician
Re: Bonding -Grounding the Neutral
A main bonding jumper is required at each disconnect. See 250.28. A grounding electrode conductor is required to each service disconnect. See 250.64(D).
Don
A main bonding jumper is required at each disconnect. See 250.28. A grounding electrode conductor is required to each service disconnect. See 250.64(D).
Don
Re: Bonding -Grounding the Neutral
I think I got it. You bond the neutrals at each disconnect, and you ground each neutral also.My next question is grounding the neutrals do you go to a water main or a ground rod ? Also how do you size the ground in the additional switches? The switches are all different sizes. Do you go to 1 ground rod or separate ones? Your help is appreciated
I think I got it. You bond the neutrals at each disconnect, and you ground each neutral also.My next question is grounding the neutrals do you go to a water main or a ground rod ? Also how do you size the ground in the additional switches? The switches are all different sizes. Do you go to 1 ground rod or separate ones? Your help is appreciated
charlie
Senior Member
- Location
- Indianapolis
Re: Bonding -Grounding the Neutral
You say you are an electrician but I am guessing you are an apprentice who is asking test questions. What say you?
You say you are an electrician but I am guessing you are an apprentice who is asking test questions. What say you?
stew
Senior Member
- Location
- federal way,washington
Re: Bonding -Grounding the Neutral
Kiss I may not be a smart as the rest of these guys either but this is how I would do this. You must first remeber that you have 2 distinct parts to this system. The gounded condutor (neutral) and the grounding electrode conductor. Both the main bonding jumper from the grounded conductor asnd the GEC are sized according to table 250.66. now in saying that most manufacturers use a green gounding screw supplied with the panel to bond the neutral buss to the panel when the panel is used as a service. Some supply a metal jumper for this purpose. Lacking either of these just use the table to determine a size based on the largest ungrounded conductor coming in to each panel. That takes care of the grounded condutor and its bonding jumper. Now you addresss the grounding electrode conductor which is a separate system but is electricall the same point within the panel. I would start form rhe grounding bar if it is the right size to accept the gec wire (if not use a lug to the can) and then continue trhu each can under a lay in lug and then out to your grounding system.In our area andaccording to 250.56 if a ground rod is used then a supplemental rod is also required 6 feet from the first per that section in most cases. Hope this helps .I am fairly certain all this meets code and if not one of the real smart guys out there will surely let me know.
Kiss I may not be a smart as the rest of these guys either but this is how I would do this. You must first remeber that you have 2 distinct parts to this system. The gounded condutor (neutral) and the grounding electrode conductor. Both the main bonding jumper from the grounded conductor asnd the GEC are sized according to table 250.66. now in saying that most manufacturers use a green gounding screw supplied with the panel to bond the neutral buss to the panel when the panel is used as a service. Some supply a metal jumper for this purpose. Lacking either of these just use the table to determine a size based on the largest ungrounded conductor coming in to each panel. That takes care of the grounded condutor and its bonding jumper. Now you addresss the grounding electrode conductor which is a separate system but is electricall the same point within the panel. I would start form rhe grounding bar if it is the right size to accept the gec wire (if not use a lug to the can) and then continue trhu each can under a lay in lug and then out to your grounding system.In our area andaccording to 250.56 if a ground rod is used then a supplemental rod is also required 6 feet from the first per that section in most cases. Hope this helps .I am fairly certain all this meets code and if not one of the real smart guys out there will surely let me know.
pierre
Senior Member
- Location
- Westchester County, New York
Re: Bonding -Grounding the Neutral
250.64(D)Grounding Electrode Conductor Taps.
This section permits you to tap off of a common grounding electrode conductor to individual service disconnects. You size the individual grounding electrode conductor taps based on the size of the phase conductor supplying the disconnect.
This is an alternative to Stew's method.
Pierre
250.64(D)Grounding Electrode Conductor Taps.
This section permits you to tap off of a common grounding electrode conductor to individual service disconnects. You size the individual grounding electrode conductor taps based on the size of the phase conductor supplying the disconnect.
This is an alternative to Stew's method.
Pierre
stew
Senior Member
- Location
- federal way,washington
Re: Bonding -Grounding the Neutral
Pierre Im thinking my method of running a single continous egc from the first can thru each of the others and attaching with a lay lug in each panel is actually a tap from an egc. At least thats the way I percieve it.And of course continuing it from the last can out to the ground rod and/or other grounds such as water pipe if avail and gas pipe if required.
Pierre Im thinking my method of running a single continous egc from the first can thru each of the others and attaching with a lay lug in each panel is actually a tap from an egc. At least thats the way I percieve it.And of course continuing it from the last can out to the ground rod and/or other grounds such as water pipe if avail and gas pipe if required.
highkvoltage
Senior Member
Re: Bonding -Grounding the Neutral
Here's a question. Wouldn't your EGC be sized to OCPD of these disconnects? Or is it the total sum of all of them? I believe it total sum. These disconnects are they for one building as in a strip mall or office building? (Just wondering doesn't effect answer). Your EGC would be based on the size of your service feeders which you stated was 1200 amp. So I'm guessing you would need 3/0 copper to the ground rod, structural steel(if any) and water lines. Any of the methods described above would work.
Here's a question. Wouldn't your EGC be sized to OCPD of these disconnects? Or is it the total sum of all of them? I believe it total sum. These disconnects are they for one building as in a strip mall or office building? (Just wondering doesn't effect answer). Your EGC would be based on the size of your service feeders which you stated was 1200 amp. So I'm guessing you would need 3/0 copper to the ground rod, structural steel(if any) and water lines. Any of the methods described above would work.
- Location
- Massachusetts
Re: Bonding -Grounding the Neutral
You never need larger than 6 AWG copper wire or 4 AWG aluminum to a ground rod.
The GEC taps are sized as Pierre described.
You never need larger than 6 AWG copper wire or 4 AWG aluminum to a ground rod.
The GEC taps are sized as Pierre described.
stew
Senior Member
- Location
- federal way,washington
Re: Bonding -Grounding the Neutral
iwire the way I understand it the #6 only applies to the portion which attaches to the ground rod right.So in this case you run a 3/0 from the service panel to the first can and continue thru each can to the last one In addition you run # 6 in the same manner starting from the first can thru the last can and out to your ground rod. Is that aq better explanation?
[ March 04, 2004, 08:38 PM: Message edited by: stew ]
iwire the way I understand it the #6 only applies to the portion which attaches to the ground rod right.So in this case you run a 3/0 from the service panel to the first can and continue thru each can to the last one In addition you run # 6 in the same manner starting from the first can thru the last can and out to your ground rod. Is that aq better explanation?
[ March 04, 2004, 08:38 PM: Message edited by: stew ]
- Location
- Massachusetts
Re: Bonding -Grounding the Neutral
Bob
Thanks Roger.
Yeah that is all I meant.
Bob
Thanks Roger.
stew
Senior Member
- Location
- federal way,washington
Re: Bonding -Grounding the Neutral
Thanks I wire we are all on the same page here.
Thanks I wire we are all on the same page here.
david
Senior Member
- Location
- Pennsylvania
Re: Bonding -Grounding the Neutral
?Now you addresss the grounding electrode conductor which is a separate system but is electricall the same point within the panel. I would start form rhe grounding bar if it is the right size to accept the gec wire (if not use a lug to the can) and then continue trhu each can under a lay in lug and then out to your grounding system.?
?(if not use a lug to the can)?
Stew
250.24 Grounding Service-Supplied Alternating-Current Systems.
(A) System Grounding Connections
(4) Main Bonding Jumper as Wire or Busbar.
Where the main bonding jumper specified in 250.28 is a wire or busbar and is installed from the neutral bar or bus to the equipment grounding terminal bar or bus in the service equipment, the grounding electrode conductor shall be permitted to be connected to the equipment grounding terminal bar or bus to which the main bonding jumper is connected
The screw or strap that you referred to can be used to bond the neutral to the can and the neutral to the equipment ground however the grounding electrode conductor needs to be connected to the same bus-bar as the neutral or to a bus bar that has a main bonding jumper that is a wire or bus bar bonding the neutral to the grounding electrode conductor
?Now you addresss the grounding electrode conductor which is a separate system but is electricall the same point within the panel. I would start form rhe grounding bar if it is the right size to accept the gec wire (if not use a lug to the can) and then continue trhu each can under a lay in lug and then out to your grounding system.?
?(if not use a lug to the can)?
Stew
250.24 Grounding Service-Supplied Alternating-Current Systems.
(A) System Grounding Connections
(4) Main Bonding Jumper as Wire or Busbar.
Where the main bonding jumper specified in 250.28 is a wire or busbar and is installed from the neutral bar or bus to the equipment grounding terminal bar or bus in the service equipment, the grounding electrode conductor shall be permitted to be connected to the equipment grounding terminal bar or bus to which the main bonding jumper is connected
The screw or strap that you referred to can be used to bond the neutral to the can and the neutral to the equipment ground however the grounding electrode conductor needs to be connected to the same bus-bar as the neutral or to a bus bar that has a main bonding jumper that is a wire or bus bar bonding the neutral to the grounding electrode conductor
stew
Senior Member
- Location
- federal way,washington
Re: Bonding -Grounding the Neutral
It seems to me it says it is permitted to be attached not required to be attached?
It seems to me it says it is permitted to be attached not required to be attached?
david
Senior Member
- Location
- Pennsylvania
Re: Bonding -Grounding the Neutral
Stew
It seems to me it says it is permitted to be attached not required to be attached?
You are exactly right, it is saying permitted to be attached. The grounding electrode conductor and the grounded conductor are required to be connected to the same point ( neutral bar) and it is a permissive statement if you do not land the grounding electrode conductor on the same bar as the neutral you have a permissive statement in 250.24 allowing the grounded electrode conductor to land on a bar(equipment grounding) that the neutral is not connected to as long as there is a main bonding jumper in the form of a bus-bar or wire bonding the two bus-bars together
[ March 05, 2004, 11:14 PM: Message edited by: david ]
Stew
It seems to me it says it is permitted to be attached not required to be attached?
You are exactly right, it is saying permitted to be attached. The grounding electrode conductor and the grounded conductor are required to be connected to the same point ( neutral bar) and it is a permissive statement if you do not land the grounding electrode conductor on the same bar as the neutral you have a permissive statement in 250.24 allowing the grounded electrode conductor to land on a bar(equipment grounding) that the neutral is not connected to as long as there is a main bonding jumper in the form of a bus-bar or wire bonding the two bus-bars together
[ March 05, 2004, 11:14 PM: Message edited by: david ]
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