Rheem Optima Owner's Manual And Installation Instructions page 32

CONNECTIONS – ELECTRICAL
WIRING DIAGRAM TWIN ELEMENT ELECTRIC WATER HEATERS
NON-SIMULTANEOUS OPERATION OFF-PEAK CONNECTION
Electrical Circuit for Twin Element Models – Robertshaw "ST" Thermostats
The active from the continuous supply must be connected to the top heating
unit circuit and the active from the Off-Peak or time controlled supply must be
connected to the bottom heating unit circuit.
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