ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Increasing demand factors in residential
by gfretwell - 03/28/24 12:43 AM
Portable generator question
by Steve Miller - 03/19/24 08:50 PM
Do we need grounding?
by NORCAL - 03/19/24 05:11 PM
240V only in a home and NEC?
by dsk - 03/19/24 06:33 AM
Cordless Tools: The Obvious Question
by renosteinke - 03/14/24 08:05 PM
New in the Gallery:
This is a new one
This is a new one
by timmp, September 24
Few pics I found
Few pics I found
by timmp, August 15
Who's Online Now
0 members (), 255 guests, and 16 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#98200 05/12/06 01:03 PM
Joined: Jun 2004
Posts: 613
S
Member
Hi guys...I'm in a debate about the size of a service lateral and the main disconnects that feed a single family dwelling.

This is how I see it...
Calculated load: 260 amps
Service lateral conductors: 2-500MCM AL and 1-350MCM AL in a 3" pvc conduit from pole to 320 amp residential meter socket.(table 310.15(B)(6) allows 500MCM at 350amps)

Then from the 320 meter I'll run 2-2" PVC conduits with 2-4/0 AL and 1-2/0 AL in each to 2-200amp main breaker panels ajacent to each other in the dwelling basement.

The other side says:
Since 500 MCM AL is only rated for 350 amps then I can NOT use 2-200amp main breaker panels...because that would require 400 amp rated service lateral conductors.

They say the panels can only be rated at 150amp each.

I said the service lateral conductors need only be rated for the load to be served.

I said I could put 6-100amp main panels in the house if I wanted and it would be code compliant.

Any comments??

thanx,

shortcircuit

Stay up to Code with the Latest NEC:


>> 2023 NEC & Related Reference & Exam Prep
2023 NEC & Related Reference & Study Guides

Pass Your Exam the FIRST TIME with the Latest NEC & Exam Prep

>> 2020 NEC & Related Reference & Study Guides
 

#98201 05/12/06 02:16 PM
Joined: Jan 2004
Posts: 1,507
G
Member
You'd be right and you could look at 230.90(A)Ex.3 as a code reference ('02 NEC)


George Little
#98202 05/12/06 02:36 PM
Joined: May 2002
Posts: 1,716
R
Member
Shortcircuit, I agree with George that you are right.

Using the "other sides" logic would mean that once you install (1) 50 amp breaker say for a range and (3) 30 amp breakers, say for water heater, dryer, and well pump, you would only be allowed to install (3) 20 amp breakers in a 200 amp panel before you'd need to up size the feeder or service.

This would mean that the required branch circuits for the Small Appliances, Bathroom, Laundry, AFC"s for Bedrooms and General lighting loads would put most 100,125,150, and 200 amp services out of any installation. [Linked Image]

Roger

#98203 05/12/06 05:25 PM
Joined: Jun 2004
Posts: 613
S
Member
Thanx George and Roger...

OK, here is another question:

Am I allowed to use 4/0 AL (XHHW/USE) to each of the 2 200amp mains according to 310.15(B)(6)?

Seems to be a gray area disputed often. But in reality, with the load diversity of dwellings, I don't think it would ever be a problem...

But also, XHHW AL is good for 180amps and the next size up breaker is 200amp...right?

shortcircuit

#98204 05/12/06 06:11 PM
Joined: Jan 2004
Posts: 1,507
G
Member
ShortCircuit- You're right again. IMHO I have heard arguements that would have you going to 250 kcmil Since we are talking a non-continious load I don't think is see an issue.


George Little
#98205 05/12/06 07:59 PM
Joined: Jun 2004
Posts: 613
S
Member
Thanx for the feedback George Little. Ummm...hope all is well with you and the rest of you guys.

Around here houses are NOT sellin and construction is slowin way down. Copper is way up...$62 for 250ft of 14-2RX and a wopping $104 for a coil of 12-2RX. This is crazy...it will become a grave situation soon if something doesn't change [Linked Image]

shortcircuit

#98206 05/12/06 08:41 PM
Joined: Mar 2001
Posts: 2,056
R
Member
Does this link help?
https://www.electrical-contractor.net/ubb/Forum2/HTML/002542.html

Similar issues, lower numbers.

[This message has been edited by Redsy (edited 05-13-2006).]

#98207 05/15/06 05:06 PM
Joined: Mar 2004
Posts: 16
J
JG Offline
Member
You are exceeding the rating of meter with two 200 amp mains: possibly this is what your inspector is saying

#98208 05/15/06 08:57 PM
Joined: Jun 2004
Posts: 613
S
Member
JG...the computed load calculation is 260amps which is well under the 320 meter sockets rating.


Link Copied to Clipboard
Powered by UBB.threads™ PHP Forum Software 7.7.5