A.O. Smith VB/VW-500 - Manual (Page 28)

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The boiler should be located in an area that is inaccessible to
the general public.
Never allow small children to use a hot water tap or to draw their
own bath water. Never leave a child or handicapped person un-
attended in a bathtub or shower.
TABLE 9. Risk of Scalds.
Temperature Time to Produce 2nd & 3rd
Setting Degree Burns on Adult Skin
Over 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) or less More than 5 minutes
SHOULD OVERHEATING OCCUR OR THE GAS SUPPLY FAIL
TO SHUT OFF, TURN OFF THE MAIN MANUAL GAS SHUTOFF
VALVE TO THE APPLIANCE.
The operating temperature of the boiler must be maintained as
follows:
• 120°F (49°C) or higher inlet water temperature to the boiler.
• 20°F (11°C) differential between the boiler’s inlet and outlet (e.g. 120°F
[49°C] inlet, 140°F [60°C] outlet minimum design temperatures).
If the inlet water temperature into the boiler is less than 120°F (49°C),
adjustments on the water bypass and the outlet valves at the rear
of the boiler, see Figures 14 and 15, are required; wait at least
one minute between adjustments for the temperature to stabilize.
1) If necessary, throttle down (close) the water outlet gate/ball
valve until the desired outlet water temperature (120°F [49°C]
minimum) is reached. Wait one minute.
2) Note the outlet and inlet temperature indicator readings.
a) If the inlet water temperature is less than 120°F (49°C),
open, in small increments, the bypass (balancing) valve
until the minimum 120°F (49°C) inlet water temperature or
20°F (11°C) differential, whichever has the higher inlet
temperature, is attained.
b) If the inlet water temperature is greater than 120°F (49°C)
and the 20°F (11°C) differential is not present, close the
bypass valve until the 20°F (11°C) differential is attained.
NOTE: It may be necessary to make further adjustments on
the outlet and bypass valves until the desired inlet and outlet
water temperatures are reached.
MANIFOLD PRESSURE CONNECTIONS
Take the manifold pressure, refer to Table 1, by removing the pipe
plug and inserting a suitable 1/8” NPT hose barb for connection to
the manometer/pressure gauge. Upon completion of
measurements and adjustments, remove the hose barb and
replace the pipe plug. Check for gas leaks and insure all
connections are gas tight, see Figure 16.
WATER TEMPERATURE REGULATION
HOT WATER CAN SCALD: Boilers 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 oth-
ers. These include the elderly, children, the infirm or physically/
mentally disabled. If anyone using hot water in your home fits
into one of theses groups or if there is a local code or state law
requiring a specific temperature water at the hot water tap, then
you must take special precautions. In addition to using the low-
est possible temperature setting that satisfies your hot water
needs, a means such as a mixing valve shall be used at the hot
water taps used by these people or at the hot water supply tank.
Mixing valves are available at plumbing supply or hardware stores.
Follow the manufacturer’s instructions for installation of the valves.
Before changing the thermostat setting on the hot water system
controller, see Table 9.
Hot water temperatures required for automatic dishwasher
and laundry use can cause scald burns resulting in serious
personal injury and/or death. The temperature at which injury
occurs varies with the person's age and time of exposure.
The slower response time of children, aged or disabled
persons increases the hazards to them. Never allow small
children to use a hot water tap, or to draw their own bath
water. Never leave a child or disabled person unattended in
a bathtub or shower.