Here's what I found in the 05 NEC:
Not exectally sure how or if it applies. Maybe Jerry can clarify this for us.
280.2 Definition.
Surge Arrester. A protective device for limiting surge voltages by discharging or bypassing surge current, and it also prevents continued flow of follow current while remaining capable of repeating these functions.
280.3 Number Required.
Where used at a point on a circuit, a surge arrester shall be connected to each ungrounded conductor. A single installation of such surge arresters shall be permitted to protect a number of interconnected circuits, provided that no circuit is exposed to surges while disconnected from the surge arresters.
230.82 Equipment Connected to the Supply Side of Service Disconnect.
Only the following equipment shall be permitted to be connected to the supply side of the service disconnecting means:
(3) Instrument transformers (current and voltage), high-impedance shunts, load management devices, and surge arresters.
???
