Sizing sub panel and wires.

[hubertyb00]

so, i need to know how to size the wires and the breaker for the subpanel. This guy has a 100 amp main panel that is full. He now wants power to his basement, so we need to put a subpanel in. To backfeed the subpanel, we are removing the range circuit from the main panel, and relocating it to the subpanel. This way we have space to feed the subpanel. so i need to know, do i do a load calc on his entire house, to see if there is enough amperage left for the basement, or do i just pop a 60 breaker in the subpanel and call it good? I can figure out how to size the wires with the code book, but i don't know how to figure the breaker size for the subpanel.
any help would be much appreciated. thanks:smile:

 

[bob]

You need to calculate the load using Article 220. There are calculators on line that will help you do this. Here is one of them

http://www.electricalknowledge.com/SFDLoadCalc.asp

 

[raider1]

I agree with Bob, you will need to do a load calculation to determine if you can do this.

Chris

 

[hubertyb00]

thanks guys
thats kinda what i was thinking but wasn't one hundred percent. So i find out what load is, just for the new basement. Or for whole house to see if he needs whole panel upgrad?

 

[raider1]

I would do a load calculation for both the new basement panel as well as the existing panel to verify that the existing panel has adequate capacity for the new basement loads.

Chris

 

[LarryFine]

To backfeed the subpanel, we are removing the range circuit from the main panel, and relocating it to the subpanel. This way we have space to feed the subpanel.

Hubert, I strongly suggest moving two 120v circuits (or at least a smaller 240v circuit) rather than the range circuit. Why have the new sub-panel feeder carry such a load? You could probably use a 30a feeder instead of a 60a (at least) one.

I always look for the smallest circuits to move when possible. If I was adding a large circuit, I'd move four small circuits to the new sub-panel, and install the new large breaker and the new sub-panel breaker in the original panel.

I do agree with doing a complete load calc first. There may already have been circuits added, which the full panel suggests. If you're adding more than lights and GP receptacles, consider an upgrade and larger panel instead of the sub.

Good luck and let us know what you end up doing.

 

[benaround]

Now that's some good advise right there

 

[wirenutt]

sub panel

sub panel

if the home only has a 100 a service and the home owner is investing $ into the basement. why doesn't he invest into a 150 a or a 200 a service. in the long run it is a more logical choice and/or investment that will be offset by the price of the subpanel and if the home goes onto the market it is more attractive.