If a high-leg is present, it should be connected in the switch so that it is protected by Fuse ___.

If a high-leg is present, it should be connected in the switch so that it is protected by Fuse ___.

• A. Fuse #2
• B. Fuse #1
• C. Fuse #3
• D. Either #1, #2, or #3

Answer: (A)

In a high-leg delta setup, the neutral comes from the center tap of one transformer winding and one leg (the high or wild leg) measures about 208 V to neutral. This leg must have its own protective device in the service disconnect so that any fault on that leg is interrupted promptly. In a common three-fuse switch arrangement, the fuse that corresponds to the high leg is the one in the middle position, so that leg is protected by that fuse’s protection. This coordination ensures a fault on the high leg is cleared without leaving that leg energized through other paths. The other two fuses protect their respective legs, but using them for the high leg wouldn’t provide proper protection for the high leg path.

In a high-leg delta setup, the neutral comes from the center tap of one transformer winding and one leg (the high or wild leg) measures about 208 V to neutral. This leg must have its own protective device in the service disconnect so that any fault on that leg is interrupted promptly. In a common three-fuse switch arrangement, the fuse that corresponds to the high leg is the one in the middle position, so that leg is protected by that fuse’s protection. This coordination ensures a fault on the high leg is cleared without leaving that leg energized through other paths. The other two fuses protect their respective legs, but using them for the high leg wouldn’t provide proper protection for the high leg path.