State SBN85 390NE A - Manual (Page 12)

12
addition adjustment maybe required later to maintain a
steady gas supply pressure.
4. When installing multiple water heaters in the same gas
supply system it is recommended that individual positive
lock-up gas pressure regulators be installed at each unit.
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.
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
infirm 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 fits 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
satisfies 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 Qualified Installer or Service Agency. Follow mixing valve
manufacturer’s instructions for installation of the valves.
taBle 6.
Water Temperature
°F (°C)
Time for 1st Degree Burn
(less Severe Burns)
Time for Permanent Burns
2nd & 3rd Degree
(Most Severe Burns)
110 (43) (normal shower temp.)
116 (47) (pain threshold)
116 (47) 35 minutes 45 minutes
122 (50) 1 minute 5 minutes
131 (55) 5 seconds 25 seconds
140 (60) 2 seconds 5 seconds
149 (65) 1 second 2 seconds
154 (68) instantaneous 1 second
(U.S. Government Memorandum, C.P.S.C., Peter l. Armstrong, Sept. 15, 1978)
gas supply system
low pressure building gas supply systems are defined as those
systems that cannot under any circumstances exceed 14”
W.C. (1/2 PSI Gauge). These systems do not require pressure
regulation. Measurements should be taken to insure that gas
pressures are stable and fall within the requirements stated on the
water heater rating plate. readings should be taken with all gas
burning equipment off (static pressure) and with all gas burning
equipment running at maximum rate (dynamic pressure). The gas
supply pressure must be stable within 1.5” W.C. from static to
dynamic pressure to provide good performance. Pressure drops
that exceed 1.5” W.C. may cause rough starting, noisy combustion
or nuisance outages. Increases or spikes in static pressure during
off cycles may cause failure to ignite or in severe cases damage to
appliance gas valves. If your low pressure system does NOT meet
these requirements, the installer is responsible for the corrections.
high Pressure building supply systems use pressures that exceed
14” W.C. (1/2 PSI Gauge). These systems must use field supplied
regulators to lower the gas pressure to less than 14” W.C. (1/2 PSI
Gauge). Appliances require gas regulators that are properly sized
for the water heater input and deliver the rating plate specified
pressures. Gas supply systems where pressure exceeds 5 PSI
often require multiple regulators to achieve desired pressures.
Systems in excess of 5 PSI building pressure should be designed
by gas delivery professionals for best performance. Water heaters
connected to gas supply systems that exceed 14” W.C. (1/2 PSI
Gauge) at any time must be equipped with a gas supply regulator.
gas pressure reQuirements
All models require a minimum gas supply pressure of 5.2” W.C.
The minimum supply pressure is measured while gas is flowing
(dynamic pressure). The supply pressure (dynamic) should never
fall below 5.2” W.C. The supply pressure should be measured
with all gas fired appliances connected to the common main
firing at full capacity. If the supply pressure drops more than 1.5”
W.C. as gas begins to flow 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 low gas pressure
switch will shut down the water heater if the supply gas pressure
drops below the minimum allowable value.
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 flowing (static pressure).
supply gas regulator
The maximum allowable gas supply pressure for this water
heater is 14.0 inches W.C. (3.48 kPa). Install a positive lock-up
gas pressure regulator in the gas supply line if inlet gas pressure
can exceed 14.0 inches W.C. (3.48 kPa) at any time.
If a positive lock-up regulator is required follow these instructions:
1. Positive lock-up gas pressure regulators must be rated at or
above the input Btu/hr rating of the water heater they supply.
2. Positive lock-up gas pressure regulator(s) should be installed no
closer than 3 feet (1 meter) and no farther than 8 feet (2.4 meters)
of equivalent length from the water heater’s inlet gas connection.
3. After installing the positive lock-up gas pressure regulator(s)
an initial nominal supply pressure setting of 7.0” W.C.
while the water heater is operating is recommended and
will generally provide good water heater operation. Some
installation reQuirements