Main Breaker Size Question

[Augus7us]

I want to get the most available slots in my new shop panel.

Is there an issue getting a panel with a 200amp main breaker that goes back to a 100amp breaker in my main panel at the house? My SE cable is all 2awg for 90amp and I'm assuming if I pulled to much current I'd still trip the 100amp in the main panel? Good or am I missing something?

Also, while I'm asking, do I need two grounding rods or just one if the resistance is 25ohms or less?

Thanks!

-Clint

 

[mike93lx]

You need a 90 in the. Ain panel, not 100.

Subpanel can be bigger,no problem. Limitation is the feeder

2 rods is easier than proving <25 ohms resistance

 

[wyliesdiesels]

I want to get the most available slots in my new shop panel.

Is there an issue getting a panel with a 200amp main breaker that goes back to a 100amp breaker in my main panel at the house? My SE cable is all 2awg for 90amp and I'm assuming if I pulled to much current I'd still trip the 100amp in the main panel? Good or am I missing something?

Also, while I'm asking, do I need two grounding rods or just one if the resistance is 25ohms or less?

Thanks!

-Clint

Is this shop detached?

If so, did you run the SE cable underground?

If so, then it should be removed and replaced as SE is not permitted underground. The bare ground will fail.

Also, is this cable 3-wire or 4-wire?

You need 2 rods unless you can PROVE 25ohms or less resistance to earth. I highly doubt you have the equipment to do so, so just drive 2 rods and be done with it.

 

[dscheidt]

If it's copper, you can do 100 A breaker, if it's aluminium, it'll need to be 90. But other than that, your thinking is correct. The panel is protected by the breaker in the main panel; the sub's main breaker serves only as a disconnect.

 

[Augus7us]

Thanks guys. I've got too many things going on apparently.

Yes, a 90amp breaker will be installed in the main panel at the house not 100.

Wylie, I'm mixing up terminology. The shop is detached and I'm running URD I believe underground to a disconnect on my house then SER I believe from the disconnect through the house to the main panel. It is four wire.

If a volt meter can't test the resistance then I'll just install another ground rod, I don't need to buy any more specialty equipment at the moment.

Hopefully I'm on the right path here.

-Clint