Thanks Lauren.
Our product is a laboratory equipment product so it is evaluated to UL/IEC/EN 61010-1 for safety. Turned out our customer is using our product to do some process on their factory floor (not what it was intended to be used for). The customer hired a third party inspector who evaluated our product to the NFPA 79 because of how the customer was using our product. The inspector didn’t like the SSR on the neutral side of a heating element and quoted 9.1.4.1. I totally agree with you that the point maybe moot. I am so glad I don’t normally deal with industrial machines because the NFPA standard is such a hard read compared to the IEC/EN standards if you are not used to it. Thanks to all, The Other Brian ________________________________ From: lauren_cr...@amat.com [mailto:lauren_cr...@amat.com] Sent: Wednesday, October 29, 2008 6:32 PM To: Kunde, Brian Cc: emc-p...@ieee.org Subject: RE: NFPA 79 Section 9.1.4.1 Brian, Well, I agree with you in that I don't see 9.1.4.1 prohibiting what the inspector claims it prohibits, but this may be a moot point. If we are speaking of a true jurisdiction electrical inspector and not a third party hired to assess the conformance of your design to NFPA 79, then it could be you just gotta do what he says. Depending on the wording of the jurisdiction's electrical legislation, the inspector may have full discretionary authority for what designs are acceptable or not. It could be, that if you had your design evaluated by a third party field evaluator to NFPA 79 and they put their sticker on your device, then the reluctant inspector might yield (it's no longer his *** on the line, its that of the field evaluator). If this inspector doesn't "get" that 9.1.4.1 is not intended for application to power circuits, other arguments are likely to be non-value added. Regards, Lauren The content of this message is Applied Materials Confidential. If you are not the intended recipient and have received this message in error, any use or distribution is prohibited. Please notify me immediately by reply e-mail and delete this message from your computer system. Thank you. Save paper and trees! Please consider the environment before printing this e-mail. "Kunde, Brian" <brian_ku...@lecotc.com> Sent by: emc-p...@ieee.org 10/28/2008 08:45 AM To Lauren Crane/APPLIED MATERIALS@AMAT cc <emc-p...@ieee.org> Subject RE: NFPA 79 Section 9.1.4.1 Lauren, When I read 9.1.4.1, I also think it is referring to the circuit driving the coil of the relay and not the heater circuit. However, the inspector is telling me this code is mandating that I cannot have a solid state relay in the Neutral side of the heater element and I don’t see his interpretation. So I was hoping that someone more familiar then I with NFPA 79 could help me out. BTW, the two thermal switches are the same kind used in cloth dryers to control temperature. They are not intended to be redundant but have different values and are located in different locations for better temp control. I’m not good at drawing schematics from ascii characters so I’ll try to better describe it. It is fairly simple. 115VAC Plug, power cord enters unit, then a double pole circuit breaker/switch. On the Line side, there is one side of an indicator light and two thermal switched in series, then the heating element. The Neutral side of the heating element connects to the other side of the indicator light, then through the contact side of a solid state relay, then back to the Mains circuit breaker/switch. The coil side of the solid state relay is controlled by a small circuit board running at 24 volts dc. The low side of the coil goes directly to logic ground. Seems simple enough. But the inspector is saying I cannot have components on both the line side and the neutral side of the heating element. When I ask why not, he says because 9.1.4.1 says so. I’m just trying to understand the code and reason for it for the future. Thanks for your time and help. The Other Brian ________________________________ From: lauren_cr...@amat.com [mailto:lauren_cr...@amat.com] Sent: Monday, October 27, 2008 6:12 PM To: Kunde, Brian Cc: emc-p...@ieee.org Subject: Re: NFPA 79 Section 9.1.4.1 It's a little hard to comment w/o a schematic. But note that under NFPA 79 there are two classes of circuits. It seems like your heater circuit may be considered a power circuit. Therefore, the inspector could be commenting on the circuit which controls the "coil" of the 24V solid state relay. Note also that even though you have two thermal switches on the line side of the heater coil it's not clear whether they are fail-safe. Redundancy doesn't add much value if the failure of the switch is not revealed somehow. Regards, Lauren Crane Product Regulatory Analyst Corporate Product EHS Lead Applied Materials Inc. - External Use - Save paper and trees! Please consider the environment before printing this e-mail. "Kunde, Brian" <brian_ku...@lecotc.com> Sent by: emc-p...@ieee.org 10/27/2008 11:53 AM To <emc-p...@ieee.org> cc Subject NFPA 79 Section 9.1.4.1 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc _________________________ 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc _________________________ 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
