Surface Temperature Test Methods Per IEEE 1349

The fine print note (FPN) No. 1 in 2005 National Electrical Code (NEC) Article 501.8 (B) [ANSI/NFPA 70, National Electrical Code, 2005 (NEC)] cautions users to "consider the temperature of internal and external surfaces that may be exposed to the flammable atmosphere" when putting a motor into service in a Class I, Division 2 environment. Thus, it is critical that manufacturers and users of industrial electric motors understand that internal peak temperatures exceed the external peak temperatures. This paper presents three common IEEE 1349 [IEEE 1349-2001, IEEE Guide for the Application of Electric Motors in Class I, Division 2 Hazardous (Classified) Locations] test methods used by manufacturers to determine these internal peak temperatures. Potential test method error and the test results from the three test methods are also presented. IEEE 1349 provides only guidance when performing these test methods so this paper intends to provide additional clarification. The test motors presented in this paper are low voltage, ac induction, severe-duty, energy-efficient, totally enclosed fan-cooled motors commonly used in the "Petrochemical Industry."