Electrical – Is it legit to use this disconnect this way

electricalsafetysubpanel

This is more an expert question for the senior users here, i.e., licensed or former electrician, and/or engineer.

I want to replace a rusted out sub panel that feeds 3 circuits at a residential dock with this Spa Panel Disconnect.

Currently the existing disconnect is fed by a 10/3 direct burial and is fused by a 30amp breaker inside the main house The existing disconnect is a main lug type.

After replacing with new disconnect, I will continue to keep it protected by the 30amp breaker inside the main house, but I'd like to back feed, yes you read me right, back feed the 50A GFCI and treat it as a main disconnect while utilizing the GFCI protection it provides to protect the smaller branch circuits "down stream" ( pun intended ).

Update With Pictures

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Best Answer

There is one major problem with your plan -- GFCI circuit breakers have LINE and LOAD terminals, and thus cannot be backfed according to Code and their Listings (according to this Square-D document, you'll fry the trip solenoid if you try). What I would do instead is change the existing 30A breaker in the main panel out for a 30A GFCI and then backfeed a disconnect switch installed in place of the subpanel's GFCI instead of using a backfed breaker or main lugs at the subpanel. This provides a single disconnecting means for the branch circuits at the subpanel.