I come across quite a few subpanels fed via SEU 3 wire here.
I had assumed (key word?)
that many older installations that included 2-wire nm followed suit with such a sub-panel feeder.(in my defense,i was not around...)
The issue comes up from time to time, as to these older subpanels being kosher, my generic answer so far is that if it met the codes at the time , yes.
A little digging here has me wondering about this.....
art 250 , "Location of Grounding Connections"
Secondary alternating curent circuits which are grounded shall have a connection to a groundingelectrode at each individual service, except as provided in section 2521.
The connection shall be made on the supply sideof the service disconnecting means.
Each secondary distribution system which is grounded shall have at least one additional connection to a grounding electrode at the transformer or elsewhere.
No connection to a grounding electrode shall be made to a grounded circuit conductor on the load side of the service disconnecting means, except as provided for in section 2524.
~note 2524 appears to be our modern 250.32
what do U think??