Did a property survey yesterday for 50KSF retail store, 2 story, partial basement, +/- 60 years old. Opened one main disc, tag states 800 amp, 250 volt, 3 phase, 4 wire..... It has 2-400 amp fuses per leg.....????
The second disc; 400 amp, 250 volt, 3 phase, 4 wire has 2-200 amp fuses per leg...???
THe line and load are both buss.... The discs were made by Federal, and the rest of the discs are "Empire"; all fused pull-outs from 100 to 400 amp.
My questions Was parallel fusing ever "legal"?? (Must have been at one time, as NJ has had inspections for a long, long time) Is this an actual 800 and 400 amp feeder??
Were the fuses physically attached or in separate clips? I have never seen it in <600 V but paralleling the barrels in one clip is quite common for obtaining higher AIC ratings in Medium Voltage applications.
Parallel Fusing sounds dangerous, I've come across this a number of times, especially where the fact is not marked. Causes a bit of confusion, if you are trying to Isolate a circuit, it's almost like a Ring Circuit, but it's not!. Pull one fuse, the voltage drops to 220 odd volts, pull another, nothing changes, try and find the other leg of the circuit. This sort of wiring, should be outlawed! Especially where Poly-Phase circuits are concerned.
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