All: I have several thousand locations where I have a single-phase service (a few are 3-phase), a transfer switch to allow me to bring in a portable generator to run the facility, and a typical load center. I am being asked to provide status of utility power ahead of the transfer switch. Technically this is a no-brainer (a 240 V relay would work nicely) but I am stumbling over how to make this NEC-compliant. NEC 230-82 tells me I can have either an instrument transformer or a "load-management device" ahead of the service disconnect, but I am foggy on how to size and protect the connection to the service entrance conductors.
I had considered installing a small 2-circuit load center with a relay on the output side of the breakers in question, but I am afraid this is overkill, and for several thousand installations any extra cost is a big negative. Is this the right approach? Assuming it is, how do I make the connection from this new load center to the service entrance conductors (which are screwed down to the appropriate lugs on the transfer switch)? Do I have to size the supply conductors the same as the 200-A service conductors? I presume so, but again I don't want to overkill.
As you can see NEC interpretation is NOT my strong suit, so I figured I'd post here and see what advice I could get.
Comments / suggestions are all welcome.
