multiple grounds in junction box?

[peter]

If you have two subpanels and they each have a circuit routed though the same metal junction box, which panel's ground wire do you use to ground the junction box? Pick just one, or use both?

[gfretwell]

Usually all the ground wires in a box are twisted together. That is not true of the neutrals unless they are all fed from a single circuit.

[maradcliff]

I agree. A ground is a ground is a ground. Both subpanels as well as all wires in junction boxes should be connected together and all of them to the ground rod(s) too.

Yes, neutrals are a different matter and should be fed from the same source as the hotwire.