The main fuses must be downstream of the disconnect switch

Electrical · System Grounding · printed page 91 (PDF page 92)

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Main Fuses Must be Downstream of Disconnect Switch Electric Service – Box

Text in the illustration

to ground
60 AMPS
service box
to distribution panel
even if the main switch is off, the fuses are still energized - a dangerous situation when changing fuses

Generated explanation

The illustration compares two fused electrical service boxes with disconnect switches, cartridge fuses, grounding connections, and outgoing conductors. In the left arrangement, incoming service conductors connect to the disconnect ahead of the fuses, and the outgoing conductors lead to the distribution panel. The right arrangement is crossed out with a red prohibition symbol and shows wiring that places the fuses electrically upstream of the disconnect. As the annotation warns, these improperly connected fuses remain energized even when the main switch is off, creating a hazard when changing fuses.