4.2.4 Temperature Rise. The temperature rises of the transformers shall be
determined by the resistance method and shall not exceed 55° C. when the
transformers are operated in air under each of the following conditions with
rated current flowing in the primary:

	A.	Rated Load
	B.	Short Circuit
	C.	Open Circuit

The temperature test shall be conducted in accordance with the applicable
requirements of the American Standard Test Code for transformers. Tempera-
ture rise shall be computed from the following formula:

Temperature Rise	(°C)	=	(234.5 + 0o) (R1 - Ro)
Where	0o	=	Temperature (°C) corresponding to Cold Resistance
	Ro	=	Cold Resistance
	R1	=	Hot Resistance