Tap Conductor over 25 feet?

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ElectricNewEngland

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New Hampshire
I have a situation where we are tapping a feeder to two VFD units. The feeder is 3#1/0 cable running from a 200A disconnect (w/ 100A fuse) at MCC to a junction box. From the junction box, we tapped 3#6 cable to a 30A disconnect (w/ 25A fuse) for VFD.
The problem is that the contractor is telling us that the run for the Tap Conductor is 50 feet or longer. I keep reading that Tap Conductors cannot be longer than 25 feet, although I cannot find that rule in the NEC codebook. I understand that Artical 240.21(B)(4) is for Tap Conductors over 25 feet, but it seems like that is only for rooms that are over 35 feet high, which our room isn't that high.
Can I just provide a bigger sized conductor for the tap (such as 3#1/0)? Should I add another disconnect to the tap conductor? I'm confused, please help. Thanks.
 
I should clarify that this is an existing installation. We are replacing a large unit with the VFDs mounted on the unit. The existing setup did not violate the 25' tap rule. But the new equipment requires us to put the VFDs on the opposite side of the equipment, thus extending the run and putting us over the 25'.
 
The basic rule (the very first sentence in 240.21) is that every conductor must be protected against overcurrent, and that the overcurrent device must be at the beginning of the run. The tap rules are essentially exceptions to that basic rule. If you tap into a feeder that has a 100 amp overcurrent device with a conductor that is only good for 65 amps (i.e., your #6 wire), then you are risking an overcurrent condition for which the feeder has inadequate protection. The tap rules allow this under very limited conditions, and the conditions are there to minimize the risk. One condition is that you keep the tap run short, and another is that you provide physical protection (i.e., to reduce the risk of their being damaged by being struck with a fork lift).

In your case, you are trying to exceed the conditions of the tap rules. Your limit is indeed 25 feet. Your choices are to install a conductor (i.e., from the junction box to the 30 amp disconnect) that can be adequately protected by a 100 amp fuse (i.e., at least a #3), or to run your #6 but insert a breaker or a fused disconnect that is no more than 25 feet from the junction box.
 
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