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54
Minimum pump performance
This is based on heating potable water with a hardness of
5 to 25 grains per gallon and/or total dissolved solids not
exceeding 350 ppm. See Water Chemistry, page 53.
TABLE 7D
Minimum Pump Performance
Model GPM FT/HD
497 - 747 55 10
987 - 2067 90 15
Heat exchanger
This is a highly sophisticated heat exchanger, designed
to carry water in such a way that it generates a scouring
action which keeps all interior surfaces free from build
up of impurities. The straight line, two pass design of
the tubes sends water into the headers at a properly
rated velocity. The configuration of the headers, in turn,
creates a high degree of turbulence which is sufficient
to keep all contaminants in suspension. This “scouring
action” provides greater cost savings for owners.
Tubes are always able to transfer heat at peak efficiency.
Every surface within this water containing section is of a
non ferrous material, providing clear, clean, rust free hot
water. Straight copper tubes finned on the outside for
maximum heat transfer and coated cast iron one piece
cored headers make up an entirely rust proof unit. On all
models, header inspection plugs can be removed for field
inspection and cleaning of copper tubes. The entire heat
exchanger may be easily removed from the unit.
Potable hot water temperature
control settings
Domestic water temperature
You must take adequate care to prevent
scald injury when storing water at elevated
temperatures for domestic use.
ƽ WARNING
This unit has an adjustable temperature control to maintain the
desired water temperature set point. See Setting Temperature
Control, page 39, for instructions to adjust the temperature
control. The temperature control is factory preset at
approximately 125°F (52°C) or less. Households with small
children or invalids may require 120°F (49°C) or lower
temperature hot water to reduce risk of scald injury.
Operate this high efficiency hot water heater at a temperature
setting high enough to prevent condensing of the products of
combustion on the unit’s heat exchanger or in the attached
venting system. A water temperature setting that is above the
dew point of the gas combustion products should prevent
condensate formation
To guard against scald injury, you must use a
properly sized thermostatic mixing valve to
supply domestic hot water at temperatures
less than 125°F (52°C).
ƽ WARNING
Return water temperatures must not be
less than 140°F (60°C). If lower return
water temperatures are required, follow the
instructions for Low Temperature Return
Water Systems, page 30.
ƽ WARNING
Installation & Service Manual
7 Domestic water heaters