what constitutes a legal local disconnect? one school of thought says you need a window to ensure you can see the stabs physically disconnect from the line side of a 3 phase system. another way is the use of "volt alerts". does anyone have an opinion on this? thanks.
Depends on the context of the question.
If referring to a LO/TO device at a piece of equipment, it does not need "visible blades", but it does need to be clearly VISIBLE with indication as to whether it is open or closed. The handle position can indicate that.
A lot of people over-interpret the way the NFPA 70E states it in the "Electrically Safe Work Conditions" section, article 120. Here is what it says:
Wherever possible, visually verify that all blades of the
disconnecting devices are fully open or that drawout type
circuit breakers are withdrawn to the fully disconnected
position.
First off, NFPA 70E is a suggestion of an electrical safety program, not a hard requirement like the NEC is. OSHA requires that everyone HAVE an electrical safety program, and offers up the NFPA 70E as a prime example, but anyone can have their own, as long as they have something that OSHA will accept if there is an accident and they investigate. Many people CHOSE to use NFPA 70E as a "safe bet" on that last part, and wisely so. But still, no a law.
Second, "
Wherever possible" is subject to interpretation. If the disconnecting device, perfectly acceptable per the NEC, is a circuit breaker, it is no possible to inspect the blades, but "visually verify" can be interpreted as looking at the handle position. This concept is actually consistently help throughout the NEC and even NFPA 79.
None of this, however, precludes a local AHJ, PoCo or Engineering Spec from requiring that all disconnects have visible blades. That's why those options exist.
