Jonathan Malton asks whether a fuse should, or is required to be user-accessible.
There is no requirement in any standard that I know of that requires a fuse to be user-accessible. Indeed, there is no requirement that a product be provided with a fuse. The requirement is that the product will not be a fire or shock hazard in the event of a single fault. If this can be done without a fuse, or can be done by relying on the facility fuse or circuit-breaker, then the construction is acceptable. (However, most electronic product fault conditions cannot provide a sufficiently or reliably low impedance to operate the facility fuse or circuit-breaker.) In today's modern electronics (especially switching-mode power supplies), if a fuse should operate, it almost always operates as a result of a true fault, i.e, a component failure, rather than as a result of negative serendipity. This means a trip to the shop for repair. If the fuse was user-accessible, then the user would replace the fuse only to see it blow again. He might be tempted to put in a larger fuse. The consequences of a larger fuse might be a truly unsafe condition. The choice of whether or not a fuse should be user-accessible is a business decision, not a safety decision. 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] | +===========================================================+
