A.O. Smith BTI 120 Installation & Operation Manual page 19

TWO TEMPERATURE - TWO PRE-HEATERS WITH MIXING VALVE OR BOOSTER
HEATER WITH OR WITHOUT BUILDING RECIRCULATION
TWO PRE-HEATERS WITH MIXING VALVE
DANGER
TEMPERATURE SETTING SHOULD NOT
EXCEED SAFE USE TEMPERATURE AT
FIXTURES. SEE WATER TEMPERATURE
CONTROL WARNING ON PAGE 25. IF HIGHER
PREHEAT TEMPERATURES ARE NECESSARY
TO OBTAIN ADEQUATE BOOSTER OUTPUT,
ADD AN ANTI-SCALD VALVE FOR HOT WATER
SUPPLIED TO FIXTURES.
TWO PRE-HEATERS WITH BOOSTER HEATER
19