In the 2020 Edition of the National Electric Code, 110.26(3) says that the clear height of the working space shall be at least "2.0 m (6 1/2 ft) or the height of the equipment, whichever is greater." Even though 2.0 m (which is 6.56168 ft) is not exactly equal to 6 1/2 ft (which is 1.9812 m), that is not a problem because 90.9(D) says, "Compliance with the numbers shown in either the SI system or the inch-pound system shall constitute compliance with this Code." So, either are equally accepted for compliance purposes of the NEC.

However, why is it "2.0" rather than just "2"? Is it for clarity reasons by just showing that 1.501 rounded up to 2 is not acceptable for this Code, is it to indicate significant figures like in measured values in hard science, or is it something else? For example, when assuming that the equipment is shorter, is a clear working height of 1.97 m, which is shorter than both of the values mentioned by the Code, complaint with the Code?

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  • "whichever is greater" covers it.
    – Solar Mike
    Sep 22 at 10:28