647 appears to address a very specific application via SDS, and as the article would deal with 'sensitive' electronics the nature of VD being mandatory supplements/modifies ( 90.3) chap's 1-4.
note how the evil nuetral* is done away with... 647.3 General.
Use of a separately derived 120-volt single-phase 3-wire system with 60 volts on each of two ungrounded conductors to a grounded neutral conductor shall be permitted for the purpose of reducing objectionable noise in senstive electronic equipment locations provided that the following conditions apply:
(1) The system is installed only in commercial or industrial occupancies.
(2) The system’s use is restricted to areas under close supervision by qualified personnel.
(3) All of the requirements in 647.4 through 647.8 are met.
my question here is, does this system supply normal 120V equipment , or is said 'equipment' rated/listed to run off the 60v/60v SDS ???
anyone?.....
*
(trade slang.....)
