Part II of Art. 210 provides the requirements for branch circuit
ratings. The first requirement is that branch circuit conductors
must have an ampacity at least as large as the load being served
[291.1(A)(1)]. However, there's a twist on the ampacity
requirements. It's called the 125% rule, and it applies to
continuous loads. You have acontinuous load when "the maximum
current is expected to continue for three hours or more” [Art.
100].  If a circuit has only noncontinuous loads, just add up
the loads to get your total load (for ampacity). Before you add
any continuous loads, you must multiply them by 125%. This rule
applies to branch circuit overcurrent protection [210.20] as
well.  The ampacity tables address only the minimum ampacities
required for safeguarding personnel and property [90.1]. For
operational efficiency, you also need to address voltage drop.
You may address it in one of two ways:    1. Increasing the
conductor size. Exceeding the ampacity table sizing by one or
two sizes is usually practica