Who determines trip curves?

[Hv&Lv]

Is it also common in the MV world to replace fuses with a piece of copper tube or a penny?

well, now that you mention it..

 

[electrofelon]

Nice!

 

[hhsting]

Another thread got me thinking about this. So clearly we have fast acting vs time delay fuses, thermal magnetic breakers, hi mag breakers, adjustable trip settings........So who or what determines what settings are acceptable to avoid conductor damage? Article 240 just seems to say "conductors shall be protected against overcurrent" with no further details. Also, OCPd's are not required to be listed, so theoretically they dont have to meet any standard. So is there anything preventing me from making a circuit breaker that has an excessively long time delay? What am I missing?

Well thats why we have coordination studies with Time Current Trip curves and cable damage curves under professional engineer supervision with his/her sign and seal. I think somewhere in 240 its does states OCPD can be selected under engineering supervision

 

[jim dungar]

i would, if i was not behind a pay wall Jim

~RJ~

Have you looked at the NEMA publications based on UL489 like, https://www.nema.org/Standards/view/Molded-Case-Circuit-Breaker-Systems-Testing-with-Conductors?

 

[romex jockey]

Have you looked at the NEMA publications based on UL489 like, https://www.nema.org/Standards/view/Molded-Case-Circuit-Breaker-Systems-Testing-with-Conductors?

i am now, thx Jim


~RJ~

 

[romex jockey]

As i suspected, it's really not that much of a test Jim......




~RJ~