I should clarify my previous reply:
Your coax circuit with 90 Vac superimposed would be NEC Class 3 if inherently current limited to 150/90 or about 1.6 amperes. “Inherently” in this context means by design and without use of external fuses or circuit breakers which could be defeated. This normally means current is limited by means of a fuse link internal to the power source or by the impedance of a transformer. Ralph From: [email protected] <[email protected]> Sent: February 27, 2026 10:22 AM To: '***** IEEE emc-pstc List *****' <[email protected]> Subject: RE: [PSES] CATV standard in USA I find the phrase, “supplied by a transformer or other device that has power-limiting characteristics” as unhelpful and unsatisfactory. A quantity like, 100 VA, would clarify the requirement. The Code‑Making Panels (CMP) and the Technical Correlating Committee (TCC) who create the NFPA 70 document are supposed to know better. For CATV using with inline amplifiers for signal leveling, the power caried in the coax can be up to about 18 Vdc and 500 mA. If you’re pushing 90 Vac on a coax, then you will need to look up the rated voltage for that coax and whether that rating is regulated by 3rd party. (e.g. UL or TUV or CSA ….) it would not be treated as Class 1, 2, or 3 as in signalling control, doorbells, and alarms system circuits. Ralph From: John Woodgate <[email protected] <mailto:[email protected]> > Sent: February 27, 2026 3:34 AM To: [email protected] <mailto:[email protected]> Subject: Re: [PSES] CATV standard in USA 'Not over 60 V' does not allow 66 V. The limit implies 54.5 V ± 10 %. On 2026-02-27 11:10, Boštjan Glavič wrote: Dear experts, I would again need your advice. We are testing the product, that is supplied through remote CATV network via coax cable. Manufacturer would like to put on the product 90Vac rating. My questions are: - what voltages are actually used in USA for CATV? In EU we normally use max 65Vac. - how is the supply voltage generated (what are requirements for power sourcing equipment)? - can supply voltage fluctuate, similar like ac mains voltage? For normal AC mains we expect fluctuation +/-10%. - should +/- tolerances to 90V be applied? I found below text in NEC 2017, which says something about 60Vac. Is this 60V fixed value or tolerances are allowed (like 66V)? 820.15 Power Limitations. Coaxial cable shall be permitted to deliver power to equipment that is directly associated with the radio frequency distribution system if the voltage is not over 60 volts and if the current is supplied by a transformer or other device that has power-limiting characteristics. Power shall be blocked from premises devices on the network that are not intended to be powered via the coaxial cable. Thank you for your valuable support. Best regards, Boštjan <https://www.siq.si/en/> <https://www.linkedin.com/company/siq> <https://www.youtube.com/channel/UCURzJFvP5CDVtL_vdvWjbQA/featured> <https://www.facebook.com/SIQLjubljana/> Boštjan Glavič Vodja laboratorija za elektroniko / Head of Laboratory Varnost in elektromagnetika / Safety and Electromagnetics SIQ Ljubljana T <tel:+386%201%204778%20265> +386 1 4778 265 / <tel:+386%2041%20391%20283> +386 41 391 283 E <mailto:[email protected]> [email protected] W <https://www.siq.si/en/> www.siq.si A Mašera‑Spasićeva ulica 10 , Ljubljana , Slovenija , SI‑1000 To elektronsko sporočilo je namenjeno izključno naslovniku. <https://www.siq.si/pravno-obvestilo-za-prejemnike-elektronske-poste/> Pravno obvestilo. The information transmitted by this email is intended only for the person or entity to which it is addressed. <https://www.siq.si/en/legal-notice-for-e-mail-recipients/> Disclaimer. _____ This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to [email protected] <mailto:[email protected]> All emc-pstc postings are archived and searchable on the web at: https://www.mail-archive.com/[email protected]/ <https://www.mail-archive.com/[email protected]/%20> Website: https://ewh.ieee.org/soc/pses/ <https://ewh.ieee.org/soc/pses/> Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to unsubscribe) <https://ewh.ieee.org/soc/pses/list.html> List rules: https://pses.ieee.org/wp-content/uploads/2024/12/EM-PSTC-List-Rules.pdf For help, send mail to the list administrators: Mike Sherman at: [email protected] <mailto:[email protected]> Rick Linford at: [email protected] <mailto:[email protected]> For policy questions, send mail to: Jim Bacher at: [email protected] <mailto:[email protected]> _____ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC <https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1> &A=1 -- Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only www.woodjohn.uk <http://www.woodjohn.uk> If something is true: * as far as we know - it's science *for certain - it's mathematics *unquestionably - it's religion <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> Virus-free. <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> www.avg.com _____ This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to [email protected] <mailto:[email protected]> All emc-pstc postings are archived and searchable on the web at: https://www.mail-archive.com/[email protected]/ <https://www.mail-archive.com/[email protected]/%20> Website: https://ewh.ieee.org/soc/pses/ <https://ewh.ieee.org/soc/pses/> Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to unsubscribe) <https://ewh.ieee.org/soc/pses/list.html> List rules: https://pses.ieee.org/wp-content/uploads/2024/12/EM-PSTC-List-Rules.pdf For help, send mail to the list administrators: Mike Sherman at: [email protected] <mailto:[email protected]> Rick Linford at: [email protected] <mailto:[email protected]> For policy questions, send mail to: Jim Bacher at: [email protected] <mailto:[email protected]> _____ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC <https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1> &A=1 - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to [email protected] All emc-pstc postings are archived and searchable on the web at: https://www.mail-archive.com/[email protected]/ Website: https://ewh.ieee.org/soc/pses/ Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to unsubscribe) List rules: https://pses.ieee.org/wp-content/uploads/2024/12/EM-PSTC-List-Rules.pdf For help, send mail to the list administrators: Mike Sherman at: [email protected] Rick Linford at: [email protected] For policy questions, send mail to: Jim Bacher: <[email protected]> _________________________________________________ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
