Subpanel

[Charlie Bob]

I'm upgrading a old 60 amp fuse box to a 100 amp breaker box.This used to be the house main panel but they left it as a subpanel for the original house, and added a 200 amp in the basement supllying this box. Since this is the old original house the load calculetion is small, they don't even use this side of the house that much. Most of it are lights and receptacles with lamps plugged into them.
I understand that the size of OCPD is based on the load. They have about 12 circuits and they may add a few lights along the way, who knows ,so i decided to go with a 100 amp box with 20 circuits space.
--Should i go by the load calculations and install a 60 amp breaker at the main 200 amp box for this subpanel or use an 80 or even a 100 amp breaker and match the rating on this subpanel?
This subpanel has a 100 amp main breaker in it.
-- Does the one protecting the feeder need to match this one too?
--And table 310.15(B)(6) doesn't apply here, right,I would have to use table 310.16. Am i correct?
Thank you all.

 

[Dennis Alwon]

You are correct T. 310.15(B)(6) does not apply unless it carries the entire load of the dwelling.

You also don't need to match the rating of the sub panel. If the panel has a 100 amp breaker then you can still use a 60 amp conductor and install a 60 amp breaker ahead of the sub.

60 amp is about as small a subpanel as I would install. You must look at the budget and decide. If you have 12 circuits of lights and recep. in this panel I suspect a 60 is large enough.

 

[LarryFine]

-- Does the one protecting the feeder need to match this one too?

The OCP at the source end of the feeder must be sized to protect the feeder (unless invoking tap rules.)

Anything downstream may be larger than required (other than the loads themselves, of course.)

 

[Charlie Bob]

got it

got it

got it!
Thank you all