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#95742 - 10/03/05 05:01 PM 310.4  
Steve T  Offline
Member
Joined: Feb 2001
Posts: 306
Oak Park, IL, USA
A building has an existing 400 amp service with a 3" rigid riser existing.

They make the service 800 amp and add another 3-1/2" riser with the same conductor type, size, insulation, length, and terminated in the same manner.

Would this be a violation?

Does the raceway having the same physical charactristics include the size of the conduit?


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#95743 - 10/03/05 05:11 PM Re: 310.4  
Ryan_J  Offline
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West Jordan, Utah, USA
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Ryan Jackson,
Salt Lake City

#95744 - 10/03/05 05:46 PM Re: 310.4  
Steve T  Offline
Member
Joined: Feb 2001
Posts: 306
Oak Park, IL, USA
Ryan--Would you mind elaborating a little. Just curious about the interpretation.

Thanks


#95745 - 10/03/05 06:16 PM Re: 310.4  
Tiger  Offline
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Joined: May 2005
Posts: 706
Crystal Lake, IL USA
SteveT, I'm curious how you turn a 400-amp service into an 800-amp service without replacing the gear. It sounds like you're describing some kind of add-on.

Dave


#95746 - 10/03/05 06:20 PM Re: 310.4  
dmattox  Offline
Member
Joined: Oct 2004
Posts: 265
Anaheim, CA
Quote
310.4 Where run in seperate raceways or cables, the raceways or cables shall have the same physical characteristics.


3" and 3 1/2" seem to be different physical characteristics to me.


#95747 - 10/03/05 06:25 PM Re: 310.4  
iwire  Offline
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Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Steve I imagine Ryan is thinking of this part of 310.4

Quote
Where run in separate raceways or cables, the raceways or cables shall have the same physical characteristics.


Tiger one quick and easy way is to provide 800 amp metering and add a second 400 amp service disconnect switch next to the original.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#95748 - 10/03/05 06:25 PM Re: 310.4  
Steve T  Offline
Member
Joined: Feb 2001
Posts: 306
Oak Park, IL, USA
They are replacing the gear.

I was just thinking the different physical characteristics tended more towards meaning the same type of metal, or not one metal and one PVC.

Does anyone have a reason why this would or could be unsafe? (Assume the raceways are properly bonded and such)


#95749 - 10/03/05 06:28 PM Re: 310.4  
dmattox  Offline
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Joined: Oct 2004
Posts: 265
Anaheim, CA
I personally don't think there would ever be an issue with this install. But you are trying to avoid any differences between the paths. If you have a smaller pipe you would have a change in heat disipation and inductance for example, which might result in one path taking a larger amount of current.


#95750 - 10/03/05 06:42 PM Re: 310.4  
iwire  Offline
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Posts: 4,391
North Attleboro, MA USA
Size is definitely a physical characteristic of a raceway.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#95751 - 10/03/05 09:13 PM Re: 310.4  
renosteinke  Offline
Cat Servant
Member
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
I thinbk that cite came from a discussion of "parallel" feeders. What I see, instead, are two separate service drops, going to two separate disconnects.

If these are then combined at a panel, I see all sorts of "multiple feed" issues."

If they are segregated from each other, all the way to the outlets, then we have two separate services on one building.

As I understand parallel feeds, they have to start, and end, at the same places.....not a separate disconnects.
If that is the case, I would have preferred a larger riser, with larger wires, coming from a single disconnect to a single weatherhead. Then, if the PoCo wanted to run a parallel feed, they would join at the weatherhead.



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