400 amp residential service

Status
Not open for further replies.

elohr46

Senior Member
Location
square one
On a 400 amp 1 phase 3 wire residential service drop, is 600 kcmil al cable needed when the service/meter socket is 320 amps? I had someone tell me that you can reduce down to 500 kcmil al. What do you guys install in this situation?
 

SEO

Senior Member
Location
Michigan
The meter socket has been derated to 320 amps based on a demand factor however if you look at table.310.15(B)(6) 600kcmil al is the min size al conductor for a residental 400 amp service.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
elohr46 said:
On a 400 amp 1 phase 3 wire residential service drop, is 600 kcmil al cable needed when the service/meter socket is 320 amps? I had someone tell me that you can reduce down to 500 kcmil al. What do you guys install in this situation?

A 400 amp meter base is capable of 400 amp noncontinuous loads. It is rated 320 amps for the continuous loads-- It makes it confusing because they don't label a 200 that way.

A 200 amp base is only good for 160 amp continuous load and 200 noncontinuous loads.

So to answer your question you need to base your conductors for 400 amps not 320 amps
 

suemarkp

Senior Member
Location
Kent, WA
Occupation
Retired Engineer
I believe you can reduce the wire size to that of the "Service". A 400A meter base does not imply a 400A service. If you need a service larger than 200A and less than 400A, you'll be using a 400A meter base. But if 250A is the rating of the single disconnect, or the calculated load comes to 250A for a multi disconnect service, then you can use wire sized for 250A.

All that being said, if I was installing a 400A meterbase, I'd probably make the service 400A also because some will assume it is capable of 400A. Or if you were contracted to install a 400A service, then I think you're stuck with installing wiring capable of that.
 
Status
Not open for further replies.
Top