I am working on a design in a Class 1 Div 2 hazardous location. Have 10 Yokogawa pressure transmitters, 24 VDC supplied, loop powered, wired to an AB Contrologix PLC. The transmitter model I selected is rated as nonincendive (NI)for Class 1 Div 2 and intrinsically safe (IS)for Class 1 Div 1. Customer wants me to use an explosionproof transmitter, arguing that my loop diagrams do not show any NI or IS wiring, which is true. How do I show NI wiring in a loop diagram? How do I argue against the explosion proof request? How do I wire the transmitters in order to conform to the nonincendive rating? According to NEC 501.4(B)(3), I can use wiring methods allowable in non-hazardous locations.
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