- Location
- Massachusetts
chris kennedy said:
So what size Earth should be used? :wink:
ground
- Thread starter Parache
- Start date
- Status
So what size Earth should be used? :wink:
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Parache said:
I don't think that you do. Could you explain your last post? we're trying to help you understand this concept.:smile:
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Parache said:
You're get there. Assuming 75C 700 MCM is good for 460 amps. not 800amps. You would have to parallel 2 pair of 700 mcm to get to 800 amps. Now look at 250.66 Note 1 below the table
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Parache said:
Good hard work. I am proud of you. See if we gave you the answer you wouldn't have learned all that you did. Keep up the hard work.
electricalperson
Senior Member
- Location
- massachusetts
:grin: :grin:
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
If you need access to the code check the links out belowrayrmelc said:
Nec 2008 Click Here
Nec 2005 Click Here
chris kennedy
Senior Member
- Location
- Miami Fla.
- Occupation
- 60 yr old tool twisting electrician
Check your PM's.rayrmelc said:
The Iceman
Senior Member
- Location
- Florida
I have a quick reference guide for copper wire size and conduit fill. I understand how to use the code book for this but when I looked at my chart under 800A it calls for 2 sets of 3-500KCM and 1-1/0 ground. Am I missing something about sizing parrallel conductors or is this chart wrong? 
- Location
- New Jersey
- Occupation
- Journeyman Electrician
The Iceman said:I have a quick reference guide for copper wire size and conduit fill. I understand how to use the code book for this but when I looked at my chart under 800A it calls for 2 sets of 3-500KCM and 1-1/0 ground. Am I missing something about sizing parrallel conductors or is this chart wrong?
That all depends on what your sizing. For an 800 amp feeder it may be correct. For the secondary conductors on a transformer to an 800 OCPD it's incorrect.
The Iceman
Senior Member
- Location
- Florida
infinity said:
Lets say its for an 800 amp feeder. Using table 310.16 the 75 degree column parralleling 500kcm only gives you 760 amps. And using table 250.66 the 1-1/0 ground would be wrong as well.
Last edited:
- Location
- New Jersey
- Occupation
- Journeyman Electrician
The Iceman said:
If the connected load is 760 amps or less then you are permitted to go up to the next standard sized OCPD which is 800 amps. According to 250.122, the #1/0 EGC would be fine and is required in both of the parallel raceways.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
The Iceman said:I have a quick reference guide for copper wire size and conduit fill. I understand how to use the code book for this but when I looked at my chart under 800A it calls for 2 sets of 3-500KCM and 1-1/0 ground. Am I missing something about sizing parrallel conductors or is this chart wrong?
If you parallel 2 500 KCM at 75C you only get 760 amps. Now if the load is less than that you can use an 800 amp breaker. So without that knowledge of what the load is you could use 600 Kcm 75C to get the full load.
Interesting that 75C 500KCM is almost equal to in ampacity to that of 700 kcm at 60C.
Why the op used 700 kcm I don't know. He could have used 600 kcm but the result was the same for the GEC. I never thought to check that.
The Iceman
Senior Member
- Location
- Florida
infinity said:
I forgot the next size up rule. Whats the article number thats under I need to review it.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
The Iceman said:
Look at 240.4(B).
- Status