A.O. Smith 400A - Manual (Page 31)

3
* PIPE RELIEF VALVE TO OPEN DRAIN.
N O T E : I F T E M P E R E D WAT E R I S
RECIRCULATED, RETURN LINE SHOULD
BE CONNECTED AT POINT “A”.
INSTALL IN ACCORDANCE WITH LOCAL
CODES.
TWO TEMPERATURE - ONE HEATER HIGH TEMPERATURE
WITH OR WITHOUT BUILDING RECIRCULATION
DANGER
TEMPERATURE SETTING SHOULD NOT EXCEED
SAFE TEMPERATURE AT FIXTURES. SEE WATER
TEMPERATURE CONTROL WARNING ON PAGE 3. IF
HIGHER PREHEAT TEMPERATURES ARE NECESSARY
TO OBTAIN ADEQUATE BOOSTER OUTPUT, ADD AN
ANTI-SCALD VALVE FOR HOT WATER SUPPLIED TO
FIXTURES.
CAUTION: IF BUILDING COLD WATER SUPPLY HAS A
BACK-FLOW PREVENTER, CHECK VALVE OR WATER
METER WITH CHECK VALVE PROVISIONS FOR
THERMAL EXPANSION OF WATER IN THE HOT WATER
SYSTEM MUST BE PROVIDED.