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12
WATER TEMPERATURE CONTROL AND MIXING VALVES
Water temperature over 125°F (52°C)
can cause severe burns instantly
resulting in severe injury or death.
Children, the elderly and the
physically or mentally disabled are at
highest risk for scald injury.
Feel water before bathing or
showering.
Temperature limiting devices such as
mixing valves must be installed
when required by codes and to
ensure safe temperatures at fixtures.
Water heated to a temperature which will satisfy clothes
washing, dish washing, and other sanitizing needs can scald
and cause permanent injury upon contact. Short repeated
heating cycles caused by small hot water uses can cause
temperatures at the point of use to exceed the water heater’s
temperature setting by up to 20°F (11°C).
Some people are more likely to be permanently injured by
hot water than others. These include the elderly, children, the
inrm and the physically/mentally disabled. Table 6 shows the
approximate time-to-burn relationship for normal adult skin. If
anyone using hot water provided by the water heater being
installed ts into one of these groups or if there is a local code
or state law requiring a certain water temperature at the point
of use, then special precautions must be taken.
In addition to using the lowest possible temperature setting
that satises the demand of the application a Mixing Valve
should be installed at the water heater (see Figure 10) or at
the hot water taps to further reduce system water temperature.
Mixing valves are available at plumbing supply stores.
Consult a Qualied Installer or Service Agency. Follow mixing
valve manufacturer’s instructions for installation of the valves.
TABLE 6.
Water Temperature
Time to Produce 2nd & 3rd
Degree Burns on Adult Skin
180°F (82°C) Nearly instantaneous
170°F (77°C) Nearly instantaneous
160°F (71°C) About 1/2 second
150°F (66°C) About 1-1/2 seconds
140°F (60°C) Less than 5 seconds
130°F (54°C) About 30 seconds
120°F (49°C) More than 5 minutes
GAS PRESSURE REQUIREMENTS
Natural gas models require a minimum gas supply pressure of
4.5” W.C. Propane gas models require a minimum gas supply
pressure of 11" W.C. The minimum supply pressure is measured
while gas is not owing (static pressure) AND while gas is owing
(dynamic pressure). The supply pressure (static and dynamic)
should never fall below the specied minimum supply pressure.
The supply pressure should be measured with all gas red
appliances connected to the common main ring at full capacity.
If the supply pressure drops more than 1.5” W.C. as gas begins
to ow to the water heater then the supply gas system including
the gas line and/or the gas regulator may be restricted or
undersized. See Supply Gas Regulator section and Gas Piping
section of this manual.
The gas valve on all models has a maximum gas supply
pressure limit of 14" W.C. The maximum supply pressure is
measured while gas is not owing (static pressure) AND while
gas is owing (dynamic pressure).
SUPPLY GAS REGULATOR
The water heater covered by this manual may require
the installation of a supply gas regulator. If the supply gas
pressure exceeds 14 inches W.C. a supply gas regulator must
be used. If the gas supply pressure exceeds 14" W.C. in a
multiple water heater installation, each water heater must
have its own supply gas regulator. If required, the supply gas
regulator shall be rated at or above the Btu/hr input rating of
the water heater it supplies.
Supply gas regulators shall have inlet and outlet connections
not less than the minimum supply gas line size for the water
heater they serve as shown in Table 9. The Maxitrol 325-7L or
equivalent is recommended.
POWER SUPPLY
The water heaters covered in this manual require a 120
VAC, 1Ø (single phase), 60Hz, 15 amp power supply and
must also be electrically grounded in accordance with local
codes or, in the absence of local codes, with the National
Electrical Code, ANSI/NFPA 70 or the Canadian Electrical
Code, CSA C22.1.
INSTALLATION REQUIREMENTS