sizing lateral for 400-amp residential service - Electrician Talk - Professional Electrical Contractors Forum
CLICK HERE AND JOIN OUR COMMUNITY TODAY, IT'S FREE!
Go Back   Electrician Talk - Professional Electrical Contractors Forum > Electrical Trade Topics > Services and Service Equipment


Like Tree22Likes
Reply
 
Thread Tools Display Modes
Old 04-05-2017, 10:48 AM   #1
Senior Member
 
Join Date: Apr 2013
Location: Rochester, NY
Posts: 312
Rewards Points: 477
Default sizing lateral for 400-amp residential service

I have a disagreement between the POCO and a sub-contractor on this, and as I've never done a service of this size and type, would appreciate some 2014 NEC feedback. 120/240 dwelling.

Existing house has 200-amp underground service, with 4/0 aluminum lateral and SEU from meter to 200-amp panel. An outbuilding is being "upfitted" with an additional 200-amp panel, and a 4/0 underground line from the house meter location to the outbuilding, to a new 200-amp panel. see my so-called diagram below. The meter enclosure is being upgraded to 320-amp. We will be replacing the existing 4/0 AL lateral, currently in 2-1/2" PVC, with larger copper. The question is, what size?

This has been approved by the POCO, with a vague nod to "whatever the code requires" for lateral sizing, "probably 250 or 350".

I contacted a larger contractor, with tuggers, winches, and the like, for a quote on replacing the lateral. He said, based on a reading of 2011 NEC table 310.15(B)(7), that the new lateral needed to have ungrounded conductors of 400 copper.

Threads I've read are all over the place on this. Suggestions or code interpretations would be greatly appreciated.


Last edited by mikewillnot; 04-05-2017 at 10:54 AM.
mikewillnot is offline   Reply With Quote
Join Contractor Talk

Join the #1 Electrician Forum Today - It's Totally Free!

ElectricianTalk.com - Are you a Professional Electrical Contractor? If so we invite you to join our community and see what it has to offer. Our site is specifically designed for you and it's the leading place for electricians to meet online. No homeowners asking DIY questions. Just fellow tradesmen who enjoy talking about their business, their trade, and anything else that comes up. No matter what your specialty is you'll find that ElectricianTalk.com is a great community to join. Best of all it's totally free!

Join ElectricianTalk.com - Click Here JOIN FOR FREE


Warning: The topics covered on this site include activities in which there exists the potential for serious injury or death. ElectricianTalk.com DOES NOT guarantee the accuracy or completeness of any information contained on this site. Always use proper safety precaution and reference reliable outside sources before attempting any construction or remodeling task!

Sponsored Links
Advertisement
 
Old 04-05-2017, 01:03 PM   #2
Senior Member
 
jw0445's Avatar
 
Join Date: Oct 2009
Location: Kirkwood, Pa.
Posts: 858
Rewards Points: 1,098
Default

This is what it says. He is correct unless you can find 350
When I do them I run 500 AL and that's in a 4" conduit with a 4" spare conduit
Your 2 1/2" conduit is a no go.

Put an 24" bull wheel on the pole and pull it with your truck.
jw0445 is offline   Reply With Quote
The Following User Says Thank You to jw0445 For This Useful Post:
Suncoast Power (04-05-2017)
Old 04-05-2017, 01:59 PM   #3
Senior Member
 
RePhase277's Avatar
 
Join Date: Feb 2008
Location: Alabama
Posts: 8,866
Rewards Points: 4,692
Default

Doesn't the POCO run the conductors in your area?
RePhase277 is online now   Reply With Quote
Old 04-05-2017, 02:26 PM   #4
Senior Member
 
Join Date: May 2015
Location: Sacramento, California
Posts: 8,811
Rewards Points: 15,898
Default

You're coming at this all the wrong way.

You need to do a Load Calculation for these buildings FIRST.

The meter sizes are quantized. [ They come in but a few 'frame sizes.' ]

That is, they jump all the way from 200A to 320A ( aka 400A) in a single bound.

This means NOTHING WRT the actual current involved.

The hefty meters can be 'backed off' by OCPD that are less than 200A times two.

YOU have to figure out what the TRUE load is... and slap in the right size fuses// C/B mains.

THEN you can back-calculate what the conductors ought to be.

Odds are strong that you are w a a a y over designing this baby.

However we can't possibly help you out with our head in a bag.

We have absolutely no idea WRT the true nature of the loads to be fed.
telsa is online now   Reply With Quote
Old 04-05-2017, 05:04 PM   #5
Fish On!
 
lighterup's Avatar
 
Join Date: Jun 2013
Location: Northeast Ohio
Posts: 1,121
Rewards Points: 2,181
Default

Quote:
Originally Posted by telsa View Post
You're coming at this all the wrong way.

You need to do a Load Calculation for these buildings FIRST.

The meter sizes are quantized. [ They come in but a few 'frame sizes.' ]

That is, they jump all the way from 200A to 320A ( aka 400A) in a single bound.

This means NOTHING WRT the actual current involved.

The hefty meters can be 'backed off' by OCPD that are less than 200A times two.

YOU have to figure out what the TRUE load is... and slap in the right size fuses// C/B mains.

THEN you can back-calculate what the conductors ought to be.

Odds are strong that you are w a a a y over designing this baby.

However we can't possibly help you out with our head in a bag.

We have absolutely no idea WRT the true nature of the loads to be fed.
Telsa.
If I may add my 2 cents.
Yes , he may very well be over killing it , BUT BUT BUT , the given info
by the HO for figuring the total connected load may not be the truth...
he would be relying on the HO to be forthright while assuming all the
liability. (This is not like a pre-engineered / approved commercial plan
where the EC can walk off with his own set of plans (for any future
reference) and proof that he/she followed the electrical engineers specs.
I think this particular electrician should throw caution to the wind and
feed the service to its rating which is 320 amps.
As Bill O'Reilly would say .."what say you..where am I going wrong here?"
lighterup is offline   Reply With Quote
Old 04-05-2017, 05:10 PM   #6
Fish On!
 
lighterup's Avatar
 
Join Date: Jun 2013
Location: Northeast Ohio
Posts: 1,121
Rewards Points: 2,181
Default

Quote:
Originally Posted by mikewillnot View Post
I have a disagreement between the POCO and a sub-contractor on this, and as I've never done a service of this size and type, would appreciate some 2014 NEC feedback. 120/240 dwelling.

Existing house has 200-amp underground service, with 4/0 aluminum lateral and SEU from meter to 200-amp panel. An outbuilding is being "upfitted" with an additional 200-amp panel, and a 4/0 underground line from the house meter location to the outbuilding, to a new 200-amp panel. see my so-called diagram below. The meter enclosure is being upgraded to 320-amp. We will be replacing the existing 4/0 AL lateral, currently in 2-1/2" PVC, with larger copper. The question is, what size?

This has been approved by the POCO, with a vague nod to "whatever the code requires" for lateral sizing, "probably 250 or 350".

I contacted a larger contractor, with tuggers, winches, and the like, for a quote on replacing the lateral. He said, based on a reading of 2011 NEC table 310.15(B)(7), that the new lateral needed to have ungrounded conductors of 400 copper.

Threads I've read are all over the place on this. Suggestions or code interpretations would be greatly appreciated.

Mikewillnot..

Why don't you just add a 2nd set of 4/0 ALURD , keeping the
first underground laterals in use and set up the service in 4/0
parrallels...either way you will be trenching because as the other
gent said , the 2-1/2" conduit will be a no go for new 400's?
Put double lugs in the new 320 amp meter socket enclosure...

Or ask public utility company & AHJ if you can set a 2nd 200 amp
service on the outbuilding?
lighterup is offline   Reply With Quote
The Following User Says Thank You to lighterup For This Useful Post:
mbednarik (04-13-2017)
Old 04-05-2017, 06:21 PM   #7
Senior Member
 
Join Date: Dec 2009
Location: Las Vegas
Posts: 346
Rewards Points: 541
Default

With this type of work is there can be requirements / defaults that apply.
Such as the utility or local amendments that by default you may need to have X size conduit, conductor size, and material.

The problem I had was in the past some of the local codes wanted RMC the entire run, buried 24", only copper, over sized conduits, and conductors sized per OCP using 310.15.

But if the utility or their authorized contractor ran it they didn't have the local amendments or NEC. So the smaller AL conductors without a conduit always came in way way less money.
active1 is offline   Reply With Quote
Old 04-05-2017, 07:17 PM   #8
Semper Fidelis
 
Suncoast Power's Avatar
 
Join Date: Jan 2009
Location: Florida
Posts: 13,623
Rewards Points: 4,900
Default

Quote:
Originally Posted by telsa View Post
You're coming at this all the wrong way.

You need to do a Load Calculation for these buildings FIRST.

The meter sizes are quantized. [ They come in but a few 'frame sizes.' ]

That is, they jump all the way from 200A to 320A ( aka 400A) in a single bound.

This means NOTHING WRT the actual current involved.

The hefty meters can be 'backed off' by OCPD that are less than 200A times two.

YOU have to figure out what the TRUE load is... and slap in the right size fuses// C/B mains.

THEN you can back-calculate what the conductors ought to be.

Odds are strong that you are w a a a y over designing this baby.

However we can't possibly help you out with our head in a bag.

We have absolutely no idea WRT the true nature of the loads to be fed.
Agreed!
That Lat should be sized for the load not the breaker math.
Suncoast Power is online now   Reply With Quote
Old 04-05-2017, 07:53 PM   #9
Senior Member
 
RePhase277's Avatar
 
Join Date: Feb 2008
Location: Alabama
Posts: 8,866
Rewards Points: 4,692
Default

I am of the opinion, over the past few years, that NEC services are oversized. And becoming more so every day.
chicken steve likes this.
RePhase277 is online now   Reply With Quote
Old 04-05-2017, 09:58 PM   #10
Senior Member
 
Join Date: Apr 2013
Location: Rochester, NY
Posts: 312
Rewards Points: 477
Default

The lateral crosses under a busy roadway, total run @170ft pole to house. POCO suggested upsizing in the existing conduit, and if possible, it makes a lot of sense.
mikewillnot is offline   Reply With Quote
Old 04-06-2017, 08:05 AM   #11
Senior Member
 
jw0445's Avatar
 
Join Date: Oct 2009
Location: Kirkwood, Pa.
Posts: 858
Rewards Points: 1,098
Default

Quote:
Originally Posted by mikewillnot View Post
The lateral crosses under a busy roadway, total run @170ft pole to house. POCO suggested upsizing in the existing conduit, and if possible, it makes a lot of sense.
Missed all of that info in your sketch. Why won't POCO set a pole on your side of the street?
MechanicalDVR and telsa like this.
jw0445 is offline   Reply With Quote
The Following User Says Thank You to jw0445 For This Useful Post:
MechanicalDVR (04-06-2017)
Old 04-06-2017, 08:24 AM   #12
still in business
 
sbrn33's Avatar
 
Join Date: Mar 2007
Location: middle america
Posts: 8,777
Rewards Points: 3,506
Default

I would honestly fit whatever size copper I can put in that 2.5 inch conduit. Then if I had to I would come up with a load calc to match it.
Just being honest and using common sense.

Edit, now that I looked at it I would run 500 aluminum in that bad boy.
__________________
but this is the economically depressed South and we're just a bunch of barefooted cousin humpers.
sbrn33 is offline   Reply With Quote
Old 04-06-2017, 09:10 AM   #13
Senior Member
 
Join Date: May 2015
Location: Sacramento, California
Posts: 8,811
Rewards Points: 15,898
Default

Quote:
Originally Posted by sbrn33 View Post
I would honestly fit whatever size copper I can put in that 2.5 inch conduit. Then if I had to I would come up with a load calc to match it.
Just being honest and using common sense.

Edit, now that I looked at it I would run 500 aluminum in that bad boy.
The new structure is a BARN.

So, I rather lean that way, myself.

I still gag at any EC that does not work up a Load Calc.
telsa is online now   Reply With Quote
Old 04-06-2017, 11:20 AM   #14
Senior Member
 
Join Date: Apr 2013
Location: Rochester, NY
Posts: 312
Rewards Points: 477
Default

I am working on the load calcs tonight. Just gathered the information today. The so-called barn is being upscaled in directions yet to be determined. Currently it is getting a sizable addition with an exercise studio, bathroom, and laundry. There is a inground pool adjacent. Who knows? Someday there may be a small apartment in there.
mikewillnot is offline   Reply With Quote
Old 04-06-2017, 08:48 PM   #15
Cow
Senior Member
 
Join Date: Jan 2008
Location: Eastern Oregon
Posts: 1,823
Rewards Points: 2,486
Default

Quote:
Originally Posted by mikewillnot View Post
The question is, what size?

This has been approved by the POCO, with a vague nod to "whatever the code requires" for lateral sizing, "probably 250 or 350".
The code only requires you size the wire to the load. 230.42.

Anything more than that, is up to you.
Cow is offline   Reply With Quote
Old 04-06-2017, 09:26 PM   #16
Senior Member
 
Join Date: May 2015
Location: Sacramento, California
Posts: 8,811
Rewards Points: 15,898
Default

Quote:
Originally Posted by RePhase277 View Post
I am of the opinion, over the past few years, that NEC services are oversized. And becoming more so every day.
Out here EUSERC rules the roost... and there is no question but that EUSERC has seriously up-sized Service Lateral standards. ( ~2001 ish )

What had been 4" PVC became 5"...

PG&E even bumped the Service Lateral standard to 3" in GRC (where it rises from the trench up into the all-in--one)... for single family homes at 200A.

That's some seriously over spec'd stuff.

They're pretty free when spending your money.

They are tight wads with their money -- on your conductors.
shocksystems likes this.
telsa is online now   Reply With Quote
Old 04-06-2017, 09:51 PM   #17
Cow
Senior Member
 
Join Date: Jan 2008
Location: Eastern Oregon
Posts: 1,823
Rewards Points: 2,486
Default

Quote:
Originally Posted by telsa View Post
Out here EUSERC rules the roost... and there is no question but that EUSERC has seriously up-sized Service Lateral standards. ( ~2001 ish )

What had been 4" PVC became 5"...

PG&E even bumped the Service Lateral standard to 3" in GRC (where it rises from the trench up into the all-in--one)... for single family homes at 200A.

That's some seriously over spec'd stuff.

They're pretty free when spending your money.

They are tight wads with their money -- on your conductors.
I wonder if living in California has anything to do with it.....?

We don't have those crazy rules where I'm at.
mbednarik likes this.
Cow is offline   Reply With Quote
Old 04-16-2017, 10:32 PM   #18
Senior Member
 
Join Date: Apr 2013
Location: Rochester, NY
Posts: 312
Rewards Points: 477
Default

Ran the load calculations, finally.
Main house - 105 amps
Barn & Addition, with future loads - 125 amps

I'm thinking 350 copper for the ungrounded conductors would fit in the 2-1/2, and also be about 20% to spare.

Now I'm wondering about how much I can undersize the neutral / ungrounded conductor. I'm thinking 250 copper -- although I imagine that will open up a can of worms here.
mikewillnot is offline   Reply With Quote
Old 04-17-2017, 06:34 AM   #19
Semper Fidelis
 
Suncoast Power's Avatar
 
Join Date: Jan 2009
Location: Florida
Posts: 13,623
Rewards Points: 4,900
Default

Quote:
Originally Posted by mikewillnot View Post
Ran the load calculations, finally.
Main house - 105 amps
Barn & Addition, with future loads - 125 amps

I'm thinking 350 copper for the ungrounded conductors would fit in the 2-1/2, and also be about 20% to spare.

Now I'm wondering about how much I can undersize the neutral / ungrounded conductor. I'm thinking 250 copper -- although I imagine that will open up a can of worms here.
You can just use the same calculation sample to find the neutral load.
Easy guess would be 70% of lighting and appliance loads and back out all 240 volt loads.
I think I would get my calculations to about 350 al with a 4/0 neutral.

You are going to install everything, turn it all on and be amused that you can only get about 60 to 80 amps after all of this.
Suncoast Power is online now   Reply With Quote
Old 04-17-2017, 07:52 AM   #20
Senior Member
 
RePhase277's Avatar
 
Join Date: Feb 2008
Location: Alabama
Posts: 8,866
Rewards Points: 4,692
Default

Three 350s can fit in a 2.5", but you're gonna find out what the term "cuss like a sailor" means.
RePhase277 is online now   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Residential 200amp Electrical service panel 13grind Services and Service Equipment 5 08-08-2016 12:18 AM
Residential Service darren79 Canadian Electrical Code Forum 29 05-26-2016 09:47 PM
400a residential service WMC Residential Electrical Forum 2 05-07-2016 07:35 AM
Help an industrial Electrician with a residential service joelowrider Services and Service Equipment 13 04-13-2016 09:01 AM
400 amp residential service water line bonding Anathera NEC Code Forum 17 03-02-2016 09:52 PM


All times are GMT -4. The time now is 01:37 PM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.1
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Our Pro Sites Network
ContractorTalk.com | DrywallTalk.com | HVACSite.com | PaintTalk.com | PlumbingZone.com | RoofingTalk.com