Hi, Bob. As a point of clarification, it's important to make the distinction of what you mean by "circuit breaker." "Circuit breaker" has long since become the name applied to the manually resettable, handle type supplementary overcurrent protectors (in some circles, calling one of these a circuit breaker will garner a swift rebuff). When the US NEC calls something a circuit breaker, it means the branch circuit overcurrent protector.
For the branch circuit device, refer to Section 210-22 of the NEC. For supplementary protectors in a product, the concerns will be primarily limited to nuisance tripping, and whether or not it provides adequate protection for your equipment under fault conditions. Here, sizing is generally at your discretion, but there are some wiring protection concepts you should be aware of in Clause 3 of the 950 based standards. If any questions arise about suitability, testing can resolve them. Regards, Peter L. Tarver Nortel ptar...@nt.com >---------- >From: Bob Brister[SMTP:bris...@mail.dec.com] >Sent: Friday, April 25, 1997 5:15 AM > >Hello, > >Are there requirements or guidelines around what a power supply input >breaker should be rated for a given nominal input current assuming the >power cord is rated appropriately? Looking through the harmonized 950 >standard I did not come across anything. > >I seem to recall seeing a 125% figure once but don't remember where that >was. I would assume that the circuit breaker would be some percent >higher than the nominal input current rating to prevent nuisance trips >and to take into account surge current or perhaps this is addressed by >the trip characteristics of the breaker. > >To give an example, if the unit has an input current rating of 16amps, >is there a rule which states the input circuit breaker must fall within >some rating range. > > >Regards, > >Bob Brister >DIGITAL >bris...@mail.dec.com >
