State SBL85 390 NE A - Manual (Page 12)

12
Some addition adjustment maybe required later to maintain
a steady gas supply pressure.
5. 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 5 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 5.
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 systems
low pressure building gas supply systems are defined as those
systems that cannot under any circumstances exceed 14” W.C.
(3.49 kPa) (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. (0.37 kPa) from static to dynamic pressure to provide
good performance. Pressure drops that exceed 1.5” W.C. (0.37
kPa) 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 water
heater 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. (3.49 kPa) (1/2 PSI Gauge). These systems must use
field supplied regulators to lower the gas pressure to less than
14” W.C. (3.49 kPa) (1/2 PSI Gauge). Water heaters 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 (34.5 kPa) 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. (3.49 kPa) (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 3.5” W.C.
(0.87 kPa) The minimum supply pressure is measured while gas
is flowing (dynamic pressure). The supply pressure (dynamic)
should never fall below 3.5” W.C. (0.87 kPa) 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. (0.37 kPa) 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 gas valve on all models has a maximum gas supply pressure
limit of 14" W.C. (3.48 kPa). 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 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 inches W.C. (3.48 kPa) at any time. regulators must
be sized/used according to manufacturer's specifications.
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. Supply gas regulators shall have inlet and outlet connections
not less than the minimum supply gas line size for the water
heater they supply. See Table 8. on page 23.
3. 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.
4. After installing the positive lock-up gas pressure regulator(s)
an initial nominal supply pressure setting of 7.0” W.C. (1.74
kPa) while the water heater is operating is recommended
and will generally provide good water heater operation.
installation reQuirements