400 Amp Service - Residential

[electrofelon]

This thread has gotten convoluted and I am not sure what's what. I see there is a meter base with 2- 200 amp breakers in it. Where is the meter base. It appears it is away from the main building, is that correct? Or are you responsible for the runs from the power company pole to the meter base on the house?

If the second concept is what you have then you would need 2 sets of 250kcm. You have to use 80% based on more than 3 current carrying conductor's in the conduit. 250 kcm @90C = 230 amps x .8 = 184. Double for parallel and you have 368 amps. Since this is a residence you can use 83% of 400 amps = 332 amps so the 250kcm will work.

But if there are two service disconnects then those conductors can be sized to the load which gives some flexibility on their sizing. I don't usually bother providing a full 400 amps for residential "400 amp" services, but maybe the op does for one reason or another.

 

[Dennis Alwon]

But if there are two service disconnects then those conductors can be sized to the load which gives some flexibility on their sizing. I don't usually bother providing a full 400 amps for residential "400 amp" services, but maybe the op does for one reason or another.

Okay so you want to use 4/0 al.... @90C that is worth 205 amps.

205 x .8 = 164 amps
164 x 2 = 328

According to the table we would need 332 amps 0r (400 x .83) so 4/0 parallel wont work. You still need 250kcm

 

[electrofelon]

Okay so you want to use 4/0 al.... @90C that is worth 205 amps.

205 x .8 = 164 amps
164 x 2 = 328

According to the table we would need 332 amps 0r (400 x .83) so 4/0 parallel wont work. You still need 250kcm

But we dont need 400 amps (not even next size down) if the load calc is ok with it per 230.90(A) exception #3.