State SBD85 500PE - Manual (Page 12)

12
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 systems
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
Natural gas models require a minimum gas supply pressure of
4.5” W.C. (1.12 kPa). Propane gas models require a minimum
gas supply pressure of 11" W.C. (2.74 kPa). The minimum supply
pressure is measured while gas is flowing (dynamic pressure).
The supply pressure (dynamic) should never fall below the
specified minimum supply pressure. 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 14.0 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. 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. 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 addition
adjustment maybe required later to maintain a steady gas
supply pressure.
installation reQuirements