Indeed, Lionel, the UL listing file rates the starters at the default values for starters of a given hp range, even with the specified fuses. I could substitute class J fuses for class RK5, since the peak let-thru current of class J, according to UL's Table SB4.2, is less than that of comparable...
Thanks again guys. I finally obtained the listing for the soft starter from Motortronics; it rates the 39 hp starter at 5kA when used with TRS (class RK5) fuses. Interestingly enough, Toshiba AS1 drives up to 50hp are also listed at 5kA when used with class J fuses. So the SCCR for the entire...
Thanks, Lionel. So I ascertain the available fault current from the one line diagram, then use the fuse curve to determine the peak let-thru amps for my fuses, then determine whether the SCCR for the starter is exceeded. This starter's SCCR, according to Toshiba tech support, is 5k(!)...
Thanks again. I've inquired with Toshiba and Motortronics about documentation of the SCCR of their starters and VFDs, and with what protective devices those ratings were achieved. The MCPs on the branch circuits will have to be supplanted by CBs with a higher SCCR to match that of the fuses, and...
Thanks, jraef. The spec calls for UL508A certification for the panel, which in turn requires a 65kAIC rating for each branch circuit. For a panel with DOL starting, I could use a combination starter and CB that were each rated for 65k (and have done so in the past). But I could not satisfy the...
You're right Lionel, but what do you make of real engineers spec'ing MCPs with soft starters and VFDs? Or calling for said combinations to be UL-approved? Many end users are willing to pay extra for a UL inspector to place a seal of approval on such mongrels; for us, that usually means boosting...
Thanks guys!
Yes, the 300A is one of 8 cam settings for instantaneous trip, and the mfr. (Cutler-Hammer) recommends the 50A MCP for this size motor, presumably for DOL starting. I was actually more concerned about blowing the fuses in the event that the end user decides to program the starter...
Friends:
I'm just the CAD guy at a panel-builder, but am often required to size CBs and fuses to satisfy specs written by real engineers. We're to build a panel for a duplex submersible sewage pump station with 20hp (27FLA) Flygt pumps and Toshiba TE-39 (19-39A) soft starters. The engineer's...
