Minuteman
Senior Member
- Location
- The Sooner Nation
Working at an industrial shop. They have several bays with 10 ton cranes. Each has 900' of crane rail all feed from 480 volt, 60 amp bus switches down to ground level unfused disconnects at the center isle. (Middle of each rail.) Some time in the past, half of bay 5 (east side) was upgraded to 20 ton by adding extra support columns.
Comes now the need for 30 ton. So, the crane company comes in and starts to "beef up" the columns some more, and we got the task of relocating whatever bus switches and raceways are in the way of the columns. Sweet gig.
The Foreman for the out-of-state crane company insists the crane rail ought to have a secondary 60 amp feed added at the far east end, due to his fear of voltage drop. The 2 new 30 ton cranes have a FLC of 34 amps, as well as the 20, 10 and 5 ton cranes already on the same rail. I told them that I could not parallel the power supplied to rail. Why not increase the supply to the rail to 100 amp?
The actual attachment to the rail has pig tales of #6 TW under a plastic cover, that is connected to #6 THHN all the way to the bus duct. The crane tech that I spoke with Friday assured me that the #6 TW is just lugged and bolted to the rail connectors and that we could change it to #3 (I suggest #2 if they are worried about voltage drop.)
One concern that I have, is that this traveling crane company may actually convince some shops to "double feed" the rail (as he calls it). OCP in parallel can't be a good thing, right?
Comes now the need for 30 ton. So, the crane company comes in and starts to "beef up" the columns some more, and we got the task of relocating whatever bus switches and raceways are in the way of the columns. Sweet gig.
The Foreman for the out-of-state crane company insists the crane rail ought to have a secondary 60 amp feed added at the far east end, due to his fear of voltage drop. The 2 new 30 ton cranes have a FLC of 34 amps, as well as the 20, 10 and 5 ton cranes already on the same rail. I told them that I could not parallel the power supplied to rail. Why not increase the supply to the rail to 100 amp?
The actual attachment to the rail has pig tales of #6 TW under a plastic cover, that is connected to #6 THHN all the way to the bus duct. The crane tech that I spoke with Friday assured me that the #6 TW is just lugged and bolted to the rail connectors and that we could change it to #3 (I suggest #2 if they are worried about voltage drop.)
One concern that I have, is that this traveling crane company may actually convince some shops to "double feed" the rail (as he calls it). OCP in parallel can't be a good thing, right?
