A.O. Smith 650A, 740A Installation & Operation Manual page 16

TWO TEMPERATURE - THREE HEATERS (TWO PRE-HEATERS/ONE BOOSTER)
CAUTION: IF BUILDING COLD WATER SUPPLY HAS A
BACKFLOW PREVENTER, CHECK VALVE OR WATER
METER WITH CHECK VALVE, PROVISIONS FOR
THERMAL EXPANSION OF WATER IN THE HOT WATER
SYSTEM MUST BE PROVIDED.
FOR MULTIPLE HEATER INSTALLATION SEE
MANIFOLD KIT SPECIFICATIONS, PAGE 18.
TWO TEMPERATURE - TWO HEATERS (ONE PRE-HEATER/ONE BOOSTER HEATER)
* PIPE RELIEF VALVE TO OPEN DRAIN.
** 140°F TO 150°F SHOULD BE MAXIMUM
WATER TEMPERATURE MAINTAINED IN THE
PRE-HEATERS.
120°F SHOULD BE THE MINIMUM
TEMPERATURE OF WATER IN THE PRE-
HEATERS.
WITH OR WITHOUT BUILDING RECIRCULATION
TEMPERATURE SETTING SHOULD NOT EXCEED SAFE TEMPERATURE AT
FIXTURES. SEE WATER TEMPERATURE CONTROL WARNING ON PAGE 23. IF
HIGHER PREHEAT TEMPERATURES ARE NECESSARY TO OBTAIN ADEQUATE
BOOSTER OUTPUT, ADD AN ANTI-SCALD VALVE FOR HOT WATER SUPPLIED TO
FIXTURES.
WITH OR WITHOUT BUILDING RECIRCULATION
CONNECT CIRCULATING LINE FROM FIXTURES, IF
USED, TO COLD WATER SUPPLY LINE OF PRE-
HEATER.
CONNECT CIRCULATING LINE OF 180°F OR BOOSTED
WATER, IF USED, TO INLET WATER LINE TO BOOSTER.
INSTALL IN ACCORDANCE WITH LOCAL CODES.
16
DANGER
CIRCULATING PUMP WIRING DIAGRAM