References: UL 198G, IEC 127 There is no such thing as a fuse that meets both standards. The gate requirements are conflict between UL 198G and IEC 127. I don't know for sure but I suspect the circuit breaker standards are similar. The UL fuse must hold 110% of rated current for one hour and clear at 135% in less than one hour. The IEC fuse must hold 150% of rated current for one hour and clear at 210% in 3 minutes, or 30 minutes depending upon the standard sheet for the particular characteristics of the fuse; ie, time lag, high breaking capacity, quick acting, low breaking capacity, etc. UL will not "List" a fuse that does not meet the UL 198G gate requirement. A CENELEC testhouse will not issue a license for a fuse that does not meet ALL applicable IEC 127 requirements, only one of which is the gate limits. FOR PROTECTION AGAINST SHORT CIRCUITS, or GROUND FAULTS - where a low impedance causes a high fault current either fuse will operate in a sufficiently short time to prevent the appliance from becoming unsafe, just as Rich Nute mentioned in his message a week or so ago. While UL will not "List" an IEC fuse, they will "Recognize" them. UL "Recognized Component" fuses are readily available with CENELEC testhouse approval marks (SEMKO, VDE and SEV are the most common). UL will NOT accept fuses according to IEC 127 in a listed product, even when approved by one of those premier CENELEC member testhouses, unless they are ALSO "Recognized Components". That sounds narrow minded but the UL position is that the fuse factory must have UL follow-up service. CSA will accept the fuse approved by a CNELEC member testhouse in a "Certified" product without question. Therefore for protection against ground faults or short circuits in a product with a rated voltage of 100V - 240V one can specify a fuse meeting the requirements of IEC 127 with a CENELEC member approval mark, AND also with UL "Recognized" component status. That scheme should not be questioned in any country and will satisfy the requirements for protection against ground faults or short circuits on any utilization circuit voltage between 100 and 240 volts. FOR PROTECTION AGAINST OVERCURRENT CONDITIONS, that is a condition where the fuse must operate within a rather narrow range, such as thermal protection for a motor or transformer, one should specify the fuse meeting the correct national requirements. UL/CSA "Listed/Certified" for North America, or an approval according to IEC 127 from a CENELEC member test house for the rest of the world. This is because the difference between the 100 - 120 volt range and the 220 - 240 volt will require a fuse with a different current rating anyway. So, the fact that the fuse standards conflict is no longer a problem. Lou Aiken 27109 Palmetto Drive Orange Beach, AL 36561 U.S.A. tel 1-334-981-6786 fax 1-334-981-3054 mobile 1-334-979-4648
