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

Reply
 
Thread Tools Search this Thread Display Modes
Old 01-19-2010, 05:06 PM   #1
Junior Member
 
Join Date: Dec 2009
Location: Scotsburn, Nova Scotia, canada
Posts: 6
Rewards Points: 10
Default 400 amp three phase service entrance

I'm a second year apprentice and i'mCurrently working on a small commerical job. The building is going to have a 400 amp three phase service. How would you go about determining the size of conducter needed to feed this building> if you where to perform a load calculation and then use wire acording to the calculation how would you make sure that later on nobody would come alonge and just add circuits. As far as i know so far i think they want to use 750 kcmil nu al to feed it. Just trying to understand how it all works. Would each wire need to be rated for 400 amps? All the code refferences on here have me confused since the cec seems to be set up differently. Thank you in advance.

jojoschauss 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!

Old 01-19-2010, 05:53 PM   #2
Senior Member
 
Join Date: Nov 2008
Location: Northern California
Posts: 221
Rewards Points: 150
Default

I prefer copper to feed panels (I've see to many problems with Aluminum.) It does cost more. But with copper I'd run parallel runs of 3/0 THHN for both grounded and ungrounded wires. If I were to run aluminum, I'd run parallel runs of 250 XHHW in 2.5" conduit. This will allow someone to fully load the panel. 750 XHHW Al. is good for 385 amps. I don't know what the nu wire is. Is that something you use in Canada? P.S. its much easier to work with the smaller wire is why we run parallel runs.

Old Spark is offline   Reply With Quote
Old 01-19-2010, 06:10 PM   #3
child please.....
 
NolaTigaBait's Avatar
 
Join Date: Oct 2008
Location: Hack City, USA aka New Orleans
Posts: 5,287
Rewards Points: 2,000
Default

You can't make sure that someone will add more later. Thats what a load calc is, it's the minimum , it doesn't provide for future expansion.
NolaTigaBait is offline   Reply With Quote
Old 01-19-2010, 07:16 PM   #4
Moderator

 
Dennis Alwon's Avatar
 
Join Date: May 2009
Location: Chapel Hill, NC
Posts: 15,628
Rewards Points: 2,374
Default

First you need to do a load calculation but if you are protecting the service with 400 amps then it would be wise to use a wire that has a 400 amp rating. Table 310.16 in the NEC will help determine this info.

Do you have a code book? Lets just assume we are not running parallel conductors. This means that each phase conductor must be able to carry 400 amps. I lets also assume we are running wires that are rated 75C.

Look at the tables. Now tell me what size copper or what size aluminum wire we will need. There are lots of things involved in deciding what size we need and we sometimes can use wires that are actually smaller than the size of the service.

For instance, if we have a 300 amp service and the calculated load is under 285 amps, then we can go to the table and see that we can actually use 300kcm copper. Why? Because article 240.4(B) allows us.
Dennis Alwon is online now   Reply With Quote
Old 01-19-2010, 07:56 PM   #5
Junior Member
 
Join Date: Dec 2009
Location: Scotsburn, Nova Scotia, canada
Posts: 6
Rewards Points: 10
Default

This building is going to be a rental building. It is going to have 3 units/stores (3 panels + house panel). At this point it is hard to determind the load since the building will later be customized to the tentants wishes. The 4in pvc for the service entrance goes underground to the pole, then up the pole and is connected up there. This conduit was already in place.
So it sounds like parallel is the way to go then ((8) 250 kcmil, but in our case having 6 current carring and 2 neutrals in one coduit there would be a derating factor there as well.
How do you determind the wire size needed when they are run in parallel.
jojoschauss is offline   Reply With Quote
Old 01-19-2010, 08:11 PM   #6
Senior Member
 
Join Date: Nov 2008
Location: Northern California
Posts: 221
Rewards Points: 150
Default

If you want to be able to fully load the 400 amp panel, then you will use two sets that can carry 200 amps. But you are correct in considering derating since you have more than 3 current carrying conductors in the conduit. With a 4" conduit you have plenty of room for either copper or alum. even with derating.
P.S. Did you guy already bid this job? What wire size was bid. Hate to up the wire size over what the boss bid without a change order.
Old Spark is offline   Reply With Quote
Old 01-19-2010, 08:31 PM   #7
Junior Member
 
Join Date: Dec 2009
Location: Scotsburn, Nova Scotia, canada
Posts: 6
Rewards Points: 10
Default

This is a time and matterial job so no bidding was required. So as long as the non linar load doesnt make up more then 50% of the total load the 2 neutrals wouldn't count as current carring conducters. Hence the derating factor would be .80 .So if we would go with david's suggestion of parallel runs of 250 XHHW aluminum.
They are rated for 205A @ 75degress
410 x .8 + 328A ussable amperage.
Yes No

thanks for all the help
jojoschauss is offline   Reply With Quote
Old 01-19-2010, 08:40 PM   #8
Senior Member
 
Join Date: Nov 2008
Location: Northern California
Posts: 221
Rewards Points: 150
Default

That's the way I read it too. Just be sure to do a good phase tape job and then double check with a continuity tester before you power up. I had a crew who phase taped every thing, but somehow did not do it right. They did'nt test either, they were so sure they did it right. Insisted someone must have been messing with them. I don't think so.
Old Spark is offline   Reply With Quote
Old 01-19-2010, 09:47 PM   #9
Moderator

 
Dennis Alwon's Avatar
 
Join Date: May 2009
Location: Chapel Hill, NC
Posts: 15,628
Rewards Points: 2,374
Default

Quote:
Originally Posted by jojoschauss View Post
This is a time and matterial job so no bidding was required. So as long as the non linar load doesnt make up more then 50% of the total load the 2 neutrals wouldn't count as current carring conducters. Hence the derating factor would be .80 .So if we would go with david's suggestion of parallel runs of 250 XHHW aluminum.
They are rated for 205A @ 75degress
410 x .8 + 328A ussable amperage.
Yes No

thanks for all the help
Yeah, you will need parallel 300KCM alum. in this case
Dennis Alwon is online now   Reply With Quote
Old 11-17-2011, 10:05 PM   #10
Junior Member
 
wire stuff's Avatar
 
Join Date: Nov 2011
Location: iowa
Posts: 1
Rewards Points: 10
Default

My boss just had us pull parallel 4/0 aluminum for our 400 amp service. We were red tagged by the inspector who made us remove our 400 amp fuses and put in 300 amp. My boss still swears up and down that he is right and is taking things up with the city.Can any one see how this size could be used any code loop holes to make this ok?
wire stuff is offline   Reply With Quote
Old 07-21-2012, 10:53 AM   #11
Junior Member
 
Join Date: Jul 2012
Location: Maryland
Posts: 13
Rewards Points: 10
Default the Service...

ok... this is all something you learn when you Get your Masters, I am a Master in the State of Maryland...

the Service Calculation is used to size the Service needed for the building... In this case, the Calculation that someone did came with with a 400Amp Service or less, the Calculation tells you to use the next higher size Main Breaker available.

You then size the Service Entrance Cables to the Breaker. This is where the problem Occurs... All terminals on all Breakers are rated to be used at 60c or 75c at most... (60 is for Romex) When you size the wire, you cannot use the 90c Column off Table 310.16 (actually this table moved in the 2011 but mine is at work, looking at a 2008 codebook now) (read the label on the side of the Breaker, it tells you what it is rated for...)

4/0 Wire is only listed for 180 amps, on the 75c column and running two of them would allow for a max service of 360amps... Next lowest breaker is 300amps which is what the inspector indicated....

A Breaker is there to protect the wire and Transformer only... The Trip timing of most breakers will only protect the equipment and not a person. GFCI's where introduced to help protect people, the same with ARC Fault.

Most Services do provide for future additions. The Demand Factors decrease with more equipment you have, why? because you are never going to use everything at the same time... Also, large scale changes require permits to be pulled and one of the things that is checked is if the new additions will exceed the existing service.. Then that just creates more income for US, because it requires the customer to upgrade the service for his proposed addition....

James
Brynn217 is offline   Reply With Quote
Old 07-21-2012, 10:57 AM   #12
Registered Member
 
Join Date: Feb 2009
Location: State of Euphoria
Posts: 14,058
Rewards Points: 2,000
Default

Quote:
Originally Posted by wire stuff View Post
My boss just had us pull parallel 4/0 aluminum for our 400 amp service. We were red tagged by the inspector who made us remove our 400 amp fuses and put in 300 amp. My boss still swears up and down that he is right and is taking things up with the city.Can any one see how this size could be used any code loop holes to make this ok?

If the calculated load on your bosses panel was not over 180 amps then you could use 4/0 al on a 200 amp breaker
mcclary's electrical is offline   Reply With Quote
Old 07-21-2012, 11:06 AM   #13
Junior Member
 
Join Date: Jul 2012
Location: Maryland
Posts: 13
Rewards Points: 10
Default Btw

In case you are wondering what the 90c column is for, that is for Sizing wire in the pipe and boxes when you need to derate the size of the wire... The Pipe Sizes are based on the number of wires in the pipe. The Breaker size is based on the size of the load in a branch circuit. Then you size the wire at 125% of the Branch Circuit Breaker, derated for The Type of Wire, # of conductors & Length of the conduit and temperature... the derating fomula uses the tempature rating of the wire you are using....

For example, you use
Brynn217 is offline   Reply With Quote
Old 07-21-2012, 11:09 AM   #14
Registered Member
 
Join Date: Feb 2009
Location: State of Euphoria
Posts: 14,058
Rewards Points: 2,000
Default

Quote:
Originally Posted by Brynn217 View Post
Then you size the wire at 125% of the Branch Circuit Breaker,


mcclary's electrical is offline   Reply With Quote
The Following User Says Thank You to mcclary's electrical For This Useful Post:
hardworkingstiff (07-21-2012)
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
Service Entrance silva.ac Services and Service Equipment 6 01-29-2009 05:51 PM
Service Entrance Conductors Absolutetruthz Services and Service Equipment 15 06-08-2008 03:16 PM
Service Entrance Panel cykoupai General Electrical Discussion 5 02-08-2008 09:26 PM
Service entrance walkerj Vintage Electrical 9 11-04-2007 12:06 AM
UG Service Entrance Hillbilly Services and Service Equipment 11 03-20-2007 09:33 PM


All times are GMT -4. The time now is 08:36 AM.


Copyright 2006-2014 Escalate Media LP. All Rights Reserved
Our Pro Sites Network
ContractorTalk.com | DrywallTalk.com | HVACSite.com | PaintTalk.com | PlumbingZone.com | RoofingTalk.com