What are the four wire and three wire connection options?
The four wire connection (preferred) connects: green ground wire to green/bare ground, red wire to red wire, black wire to black wire, and white wire to white/gray neutral. The three wire connection (acceptable where codes permit) connects: red to red, black to black, and both green and white wires to the white/gray neutral wire.
From the official Bosch HBL503 500 Series Single Wall Oven manual, page 6
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