How much space do you need around electrical equipment operating at 600V or less? Judging from the typical installation, it must be about 2 ft - 11 in. deep by slightly wider than the equipment. For distribution panels in offices, that’s often after moving boxes, filing cabinets, or bookshelves. For commercial and industrial spaces, you often get that room around transformers after moving loaded pallets or other heavy objects out of the way.
The reason for the 2 ft - 11 in. of space is it’s “close enough to the three foot requirement.” But “the three foot requirement” is a myth. The bare minimum of depth is three feet, but that minimum may increase to four feet depending upon conditions [Table 110.26(A)(1)].
Because OSHA copies the space requirements directly from Sec. 110.26, the NEC space requirements have the force of federal law. Being an inch short isn’t “close enough,” it’s inadequate.
Critical concept: the NEC does not tell you exactly how much space you need. It just says, “If you go below X under Y conditions, that’s a Code violation.” And OSHA says the same thing.
The very first sentence of Sec. 110.26 requires enough space around all electrical equipment “to permit ready and safe operation of such equipment.” How much is that?
