Ran into this today: Recent new spa install using power from a Zinsco sub-panel. Cable from sub-panel to spa gfi breaker is 6 guage 3 with ground. Neutrals and grounds are not seperated in the Zinsco box. The neutral to the Spa Breaker runs from the buss in the Zinsco to the neutral bus on the spa panel. The gfi on the spa panel has the load neutral to the breaker and the breaker neutral to the bus. All of this is 6 gauge wire except the ground to the spa from the spa panel. This is 12 gauge. It is hooked to the neutral bus on the spa panel. My question is this: Is this spa gfi breaker actually able to "protect"? It tests out fine with the test button. Am I missing something? There is no complaint from the owner. I am doing another repair on the system when I ran into this. thanks for your input.