Dear Experts,
Can anyone please explain to me section 9.1.4.1 of NFPA 79? (see below) NFPA 79 9.1.4 Connection of Control Circuit Devices. 9.1.4.1 All operating coils of electromechanical magnetic devices and indicator lamps (or transformer primary windings for indicator lamps) shall be directly connected to the same side of the control circuit. All control circuit contacts shall be connected between the coil and the other side of the control circuit. A safety inspector is telling me the following circuit is in violation of the above requirements: 115VAC Heating Element wired with a solid state relay (for circuit on/off, not for temperature control) on the Neutral side of the heating element. There are several thermal switches on the Line side of the heating element. The relay is controlled by a 24 volt circuit and ground. There is a manual power switch that opens both sides of the line. If the relay failed in a short condition or if the neutral side of the heating element shorts to chassis ground , no hazard occurs because the temperature is controlled by two thermal switches. How would this circuit violate 9.1.4.1? The safety inspector is saying that this section of the standard mandates the solid state relay must be on the Line side of the heating element along with the thermal switches. Is he correct? Thank you for your help. The Other Brian _________________________ LECO Corporation Notice: This communication may contain confidential information intended for the named recipient(s) only. If you received this by mistake, please destroy it and notify us of the error. Thank you. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
