400 Amp Service

Status
Not open for further replies.
C

Canton

Senior Member
Location
Virginia
Occupation
Electrician
I think we have had this discussion before......

Residential 400 amp services
Two 200 amp panels
Two sets of 4/0 aluminum SE cable, one feeding each MB panel

Code compliant...or not?

I'm gonna get some popcorn 🍿 and watch....
 
Size of conductors/ampacity. Can 4/0 aluminum be used in a residential application for a 400 amp service feeding two 200 amp panels?

I'm getting at the 83% rule/diversity of the loads/ and if they carry the entire load of the dwelling.
 
Our state kept 310.15(B)(7)...;)
 
Last edited:
Canton said:
Size of conductors/ampacity. Can 4/0 aluminum be used in a residential application for a 400 amp service feeding two 200 amp panels?

I'm getting at the 83% rule/diversity of the loads/ and if they carry the entire load of the dwelling.
Click to expand...
You do not even need the 83% rule if the calculated load on each panel is 180 amps or less per the next size up rule.
 
Here it is accepted routinely even though a load calculation on each panel could be requested.

(actually 2/0 Cu is also)
 
augie47 said:
Here it is accepted routinely even though a load calculation on each panel could be requested.

(actually 2/0 Cu is also)
Click to expand...

Load calculations on residential services are rarely done here.

Can the reduced service conductor table/83% rule be used in this application for a 400 amp service (meter) feeding two 200 amp panels with 4/0 SE cable?

I would say no, as the service conductors do not carry all of the dwelling load, they are split up.

Would it then require larger SE conductors?
 
augie47 said:
Here it is accepted routinely even though a load calculation on each panel could be requested.

(actually 2/0 Cu is also)
Click to expand...
I would think and interpretate on 2/0 copper, if not supplying entire load(which will not be with 2 panels) , you must size over current protection device to its next standard size breaker which is 175A.
Load calculation could also be requested on 4/0 Al too, but as Infinity stated would have to be no more than 180A.
Thoughts?
 
infinity said:
You do not even need the 83% rule if the calculated load on each panel is 180 amps or less per the next size up rule.
Click to expand...

Greentagger said:
I would think and interpretate on 2/0 copper, if not supplying entire load(which will not be with 2 panels) , you must size over current protection device to its next standard size breaker which is 175A.
Load calculation could also be requested on 4/0 Al too, but as Infinity stated would have to be no more than 180A.
Thoughts?
Click to expand...
Ok, let's say calculated load is 351 amps. 175 amps will be installed into one panel, and 176 amps will be installed in the other.

Electrician installs (2) 200 panels with 4/0 aluminum SE to each. Compliant, or no?
 
Canton said:
Ok, let's say calculated load is 351 amps. 175 amps will be installed into one panel, and 176 amps will be installed in the other.

Electrician installs (2) 200 panels with 4/0 aluminum SE to each. Compliant, or no?
Click to expand...
Compliant because the next size up rule would allow the 180 amp conductor to be protected at 200 amps.
 
electrofelon said:
Today I did a "400 amp" single phase service to a 5 gang meter pack for 4 dwelling units plus house panel. Two sets of 4/0 AL in same pipe. Technically it's a 288 amp service.
Click to expand...


Technically, do you have to show load calculations for the 5 to be no more than 288 amps?
 
Status
Not open for further replies.
Top