Have you tried the Frank D. Petruzella book " Programmable Logic Controllers". i have found it usefull in many ways. Consider obtaining a ladder logic diagram.
I would like some information on Transformer Feeder tap rules above and beyond what i have found in the nec 240.21 (B)(4). Concerning the horizontal length rule. Can this rule be used in commerical buildings or is it limted to manufacturing building only?