I am currently helping to install a new service to a building. Service is 3000A,3-Ph.,4W,208V-feed comes from new pad mounted outdoor X-former and feeds main disc. inside building. Partner says we need to "bond" at both X-former and Main disc. I say we could "bond" at either place, but it is not acceptable to bond at both places. Am I right? If so hows about some NEC code sections to shut him up.
Main Bonding Jumper
- Thread starter ibew236
- Start date
- Status
- Location
- Illinois
- Occupation
- retired electrician
Re: Main Bonding Jumper
Look at 250.24(A)(2).
Don
Look at 250.24(A)(2).
Don
- Location
- Massachusetts
Re: Main Bonding Jumper
You should be checking out the reference Don pointed out in the 2002 book.
In 1996 250.23 is close to the same as 2002 250.24
Beyond that you do bond at the transformer and at the service disconnect.
You do not run an equipment grounding conductor between the transformer and the service disconnect, only the ungrounded and grounded conductors.
If you did not bond at the transformer and the transformer has a fault to the enclosure what would make the POCOs over current device operate?
You need to bond the transformers enclosure to the Neutral to create a short circuit if a fault to the enclosure happens.
[ February 03, 2004, 09:16 PM: Message edited by: iwire ]
You should be checking out the reference Don pointed out in the 2002 book.
In 1996 250.23 is close to the same as 2002 250.24
Beyond that you do bond at the transformer and at the service disconnect.
You do not run an equipment grounding conductor between the transformer and the service disconnect, only the ungrounded and grounded conductors.
If you did not bond at the transformer and the transformer has a fault to the enclosure what would make the POCOs over current device operate?
You need to bond the transformers enclosure to the Neutral to create a short circuit if a fault to the enclosure happens.
[ February 03, 2004, 09:16 PM: Message edited by: iwire ]
Re: Main Bonding Jumper
What about if the transformer is inside? Code 250.24(A)(2) refers to transformers installed outside a building. I have a site with a generator that feeds a delta/wye (indoor) transformer. They are using a 3-pole ATS. So, in this application you will always have the neutral-ground bond at the main service panel. If you also have a bond on the generator transformer XO wouldn't this create a parallel path for current???
What about if the transformer is inside? Code 250.24(A)(2) refers to transformers installed outside a building. I have a site with a generator that feeds a delta/wye (indoor) transformer. They are using a 3-pole ATS. So, in this application you will always have the neutral-ground bond at the main service panel. If you also have a bond on the generator transformer XO wouldn't this create a parallel path for current???
Re: Main Bonding Jumper
Hey everybody, I've answered my own question about the code for the generator transformer in my previous post. Because this generator transformer is connected to a 3-pole ATS, in which the neutral is tied together with the utility neutral, this would be covered under 250.20(D)(FPN No. 1). Therefore the transformer is not a seperately derived source and therefore should not be bonded.
Hey everybody, I've answered my own question about the code for the generator transformer in my previous post. Because this generator transformer is connected to a 3-pole ATS, in which the neutral is tied together with the utility neutral, this would be covered under 250.20(D)(FPN No. 1). Therefore the transformer is not a seperately derived source and therefore should not be bonded.
- Status