Chapter 9, Problem 1RQ

How does the National Electrical Code specify that the high leg of a four-wire delta connection be marked?

To determine

The method specified by the National Electrical Code for the marking of the high leg of a four-wire delta connection.

Explanation of Solution

High delta leg is a type of electrical service connection which is also termed as wild leg, stinger leg, orange leg or red leg delta.

Whenever there is a need of power supply of both three phases and single phase power from a three phase transformer, high delta leg comes into use. The high delta leg voltage is $1.732$ times the single phase, center tapped voltage.

The specification for the marking of the high delta leg for a four wire delta connection is provided by National Electrical Code. As per this specification, the high delta leg must be connected to an orange wire or tagged at any point where a connection is made.

Thus, the National Electrical Code specifies that the high leg of a four-wire delta connection be marked by connecting it to an orange wire or by tagging it any point where a connection is made.