[Code of Federal Regulations] [Title 46, Volume 4] [Revised as of October 1, 2005] From the U.S. Government Printing Office via GPO Access [CITE: 46CFR111.20-5] [Page 222] TITLE 46--SHIPPING CHAPTER I--COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PART 111_ELECTRIC SYSTEMS_GENERAL REQUIREMENTS--Table of Contents Subpart 111.20_Transformer Construction, Installation, and Protection Sec. 111.20-5 Temperature rise. (a) The temperature rise, based on an ambient temperature of 40 degrees C, must not exceed the following: (1) For Class A insulation, 55 degrees C. (2) For Class B insulation, 80 degrees C. (3) For Class F insulation, 115 degrees C. (4) For Class H insulation, 150 degrees C. (b) If the ambient temperature is higher than 40 degrees C, the transformer must be derated so that the total temperature stated in this section is not exceeded. The temperature must be taken by the resistance method.