Hello from San Diego:
Mark Werlwas asks about the source for Annex F (Protection against the spread of fire) of IEC 1010-1. The Limited Circuit definition probably comes from the USA National Electrical Code and Canadiain Electrical Code definitions for "Class 2" circuits. I believe the same definition appeared in UL 1244, one of the predecessors to IEC 1010-1. (It was also used in UL 478, the early ITE safety standard.) The reduction of risk of fire in unlimited circuits is probably a combination of requirements from CSA and other sources. CSA used the concept of "reduction of risk" in several of its older bulletins and standards, including its predecessor to IEC 1010-1. UL did not use this concept. Certainly the requirement for energization only when a switch is held closed is a more-or-less classical requirement to require an operator presence who would detect any fire. I believe this concept appeared in the early CEE (22?) standard for office equipment. (You can think of CEE as being the predecessor to EN standards.) I believe the requirement for all motors and transformers to have overcurrent and overtemperature protections is also from CSA. Bottom opening requirements were originally specified in UL and CSA proprietary standards for office and other equipment, and was picked up by their respective test equipment proprietary standards. Subsequently, they were adopted into IEC 1010-1. If you want the sources for these requirements, I suggest you obtain a copy of the early editions of UL 1244 and the CSA Bulletins covering test and measurement equipment and laboratory equipment. You might also obtain copies of UL 114, UL 478, and CSA 220. All of these are out of print and no longer stocked by either UL or CSA. Nevertheless, I would inquire of both organizations. Perhaps someone can find copies, or will be willing to copy one for you. Best regards, Rich ------------------------------------------------------------- Richard Nute Quality Department Hewlett-Packard Company Product Regulations Group San Diego Division (SDD) Tel : 619 655 3329 16399 West Bernardo Drive FAX : 619 655 4979 San Diego, California 92127 e-mail: [email protected] -------------------------------------------------------------
