John Wood JW375T75N-AV, Instruction Manual

Page: 20 / 36

20
START UP CONDITIONS
DRAFT HOOD OPERATION
Check draft hood operation by performing a worst case
depressurization of the building. With all doors and windows
closed, and with all air handling equipment and exhaust fans
operating such as furnaces, clothes dryers, range hoods and
bathroom fans, a match flame should still be drawn into the draft
hood of the water heater with its burner firing. If the flame is not
drawn toward the draft hood, shut off water heater and make
necessary air supply changes to correct.
CONDENSATION
Whenever the water heater is filled with cold water, some
condensate will form while the burner is on. A water heater may
Short repeated heating cycles caused by small hot water uses can
cause temperatures at the point of use to exceed the thermostat
setting by up to 30°F (16.7°C). If you experience this type of use
you should consider using lower temperature settings to reduce
scald hazards.
Any water heater’s intended purpose is to heat water. Hot water
is needed for cleansing, cleaning, and sanitizing (bodies, dishes,
clothing). Untempered hot water can present a scald hazard.
Depending on the time element, and the people involved (adults,
children, elderly, infirm, etc.) scalding may occur at different
temperatures.
HOTTER WATER CAN SCALD: Water heaters are intended to
produce hot water. Water heated to a temperature which will satisfy
space heating, clothes washing, dish washing, and other sanitizing
needs can scald and permanently injure you upon contact. Some
people are more likely to be permanently injured by hot water than
others. These include the elderly, children, the infirm, or physically/
mentally handicapped. If anyone using hot water in your home fits
into one of these groups or if there is a local code requiring a certain
temperature water at the hot water tap, then you must take special
precautions. In addition to using the lowest possible temperature
setting that satisfies your hot water needs, a means such as a mixing
valve should be used at the hot water taps used by these people or
at the water heater. Mixing valves are available at plumbing supply or
hardware stores, see Figure 2. Follow manufacturer’s instructions for
installation of the valves. Before changing the factory setting on the
thermostat, read the “Temperature Regulation” section in this manual,
see Figures 17 and 18.
TEMPERATURE REGULATION
FOR YOUR INFORMATION
appear to be leaking when in fact the water is condensation. This
usually happens when:
a. A new water heater is filled with cold water for the first time.
b. Burning gas produces water vapor in water heaters, particularly
high efficiency models where flue temperatures are lower.
c. Large amounts of hot water are used in a short time and the
refill water in the tank is very cold.
Moisture from the products of combustion condense on the cooler
tank surfaces and form drops of water which may fall onto the
burner or other hot surfaces to produce a “sizzling” or “frying” noise.
Excessive condensation can cause pilot outage due to water
running down the flue tube onto the main burner and putting out
the pilot.
Never allow small children to use a hot water tap, or to draw their own
bath water. Never leave a child or handicapped person unattended
in a bathtub or shower.
NOTE: A water temperature range of 120°F-140°F (49°C-60°C) is
recommended by most dishwasher manufacturers.
The thermostat of this water heater has been factory set at its lowest
position (PILOT LIGHTING ). It is adjustable and must be reset to
the desired temperature setting to reduce the risk of scald injury.
The mark ( ) indicative of approximately 120°F (49°C) is preferred
starting point. Some States have a requirement for a lower setting.
Turn the water temperature dial clockwise ( ) to decrease the
temperature, or counterclockwise ( ) to increase the temperature.
Should overheating occur or the gas supply fail to shut off, turn off the
manual gas control valve to the water heater.
FIGURE 17.
Water
Temperature °F
Time for
1st Degree Burn
(Less Severe Burns)
Time for Permanent Burns
2nd & 3rd Degree
(Most Severe Burns)
110 (normal shower temp.)
116 (pain threshold)
116 35 minutes 45 minutes
122 1 minute 5 minutes
131 5 seconds 25 seconds
140 2 seconds 5 seconds
149 1 second 2 seconds
154 instantaneous 1 second
(U.S. Government Memorandum, C.P.S.C., Peter L. Armstrong, Sept. 15,1978)
FIGURE 18.