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Commercial Electric Hot Water Boilers
A. O. Smith’s Electric Boilers are designed for demanding hydronic and industrial heating
needs. A wide variety of available electrical inputs and voltages allow the units to be
perfectly matched to the heating requirements of the application and the available
electrical services.
FEATURES
MODULATING STEP CONTROL
input to match load through progressive sequencing of steps. Standard on models with 90kW
or above (optional below 90kW).
INCOLOY IMMERSION HEATERS
immersion heater) have incoloy sheathing, provides excellent protection against oxidation and
scaling. The input ranges from 45kW to 6,000kW (see accompanying chart).
OPTIONAL GOLDENROD® ELEMENTS
24K gold plated element. Goldenrod Elements provide long-life and fi ve times the scaling resistance
of standard incoloy elements. Goldenrod Elements carry a three-year warranty against failure due
to scale.
FUSING -
cartridge-type fuses protect all elements and contactors.
Control and power circuit fusing to meet the National Electrical Code. 100,000 amp I.C.
PILOT SWITCH AND LIGHT
by interrupting power to control circuit. Pilot light indicates when control circuit
is energized.
MAGNETIC CONTACTORS
LOW WATER CUTOFF
in the event of low water condition.
- Probe type, electric low water cutoff prevent energizing of elements
- A solid state modulating step control modulates heat
- Heavy duty medium watt density elements (3 per
- All NW models are available with the Goldenrod
-
Permits manual starting and stopping of heater
- Heavy duty UL rated for 100,000 cycles.
NW-37
through
NW-670
®
120 VOLT CONTROL CIRCUIT
ASME CODE CONSTRUCTION
Vessels with maximum working pressure of 160 psi or less (standard design is for 125 psi) at 240°F
maximum temperature bear the “H” symbol per Section IV of ASME Code. Vessels with greater
than 160 psi working pressure or higher than 240°F operating temperature will bear the “S” symbol
per Section I of ASME Code.
UL LISTED
- All boilers are UL listed per Underwriters’ Laboratories Standard No. 834.
- Powered by fused transformer.
- All vessels manufactured to applicable ASME Code.
ONE YEAR LIMITED WARRANTY
Q
For complete warranty information, consult written warranty.
OTHER STANDARD FEATURES
Q
Two high temperature limit controls
Q
Cabinet has a baked powder coat fi nish
Q
Rectangular jacket made with 18 gauge (minimum) steel
Q
3” fi ber glass insulation
Q
Color coded circuitry for easier servicing
Q
Standard voltages include 208, 240, 480 and 575 volt, single or three-phase
Q
Factory installed terminal block(s)
Q
Combination Temperature/Pressure Gauge
Q
Boiler drain valve
Q
CSA Certifi ed and ASME Rated T&P Relief Valve
*Model shown with optional accessories
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Commercial Electric Hot Water Boilers
UL MINIMUM CLEARANCE REQUIRMENTS:
24” ALL SIDES, 12” TOP
NOTE: ALLOW 30” CLEARANCE FOR HINGED CONTROL
COMPARTMENT DOORS.
ELEMENTS CAN BE CHANGED WITH 24” CLEARANCE.
AN ADDITIONAL CONTROL PANEL IS REQUIRED ON
UNITS ABOVE 500kW RATED AT 208 OR 240 VOLTS.
MODELS: NW-37, NW-60, NW-96 AND NW-150
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MODELS: NW-220, NW-334, NW-400, NW-500 AND NW-670
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Maximum
kW
Input
NOTE: For boilers 3400kW to 6000kW, consult factory.
Commercial Electric Hot Water Boilers
Std. kW
Input
Standard Number
and kW of Steps
NOTE: 1. For boilers 3400kW to 6000kW, consult factory.
2. Other voltages available.
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Commercial Electric Hot Water Boilers
OPTIONAL CONTROL FEATURES
MODULATING STEP CONTROL WITH SCR – Element
modulation with an SCR slave between steps.
MANUAL RESET LOW WATER CUTOFF - Available factory
mounted to meet local codes or specifi cations. Float type or
probe type are available.
MANUAL RESET HI-LIMIT – A control that, in the event of
temperature condition interrupts control circuit de-energizing
elements, must be manually reset.
SAFETY DOOR INTERLOCK – Prevents opening of control panel
door when boiler supply is on. NOTE: Once door is opened boiler
may be energized if
INDICATING LIGHTS AND OVERRIDE SWITCHES – A simple
form of load control allows all or part of unit input to be
controlled manually. Up to one indicating light and override
switch per contactor is available.
CIRCUIT BREAKER – Factory mounted, available for those
installations where there is no breaker at the electrical
powersource, or the breaker is not within sight of the boiler.
Asafety device which disconnects power to the heater in the
event of overcurrent.
GROUND FAULT INTERRUPTER – A safety device
(circuit breaker) which disconnects power to the heater in the
event of a curr
set point value; breaker must
SHUNT TRIP CIRCUIT BREAKER – A safety device (circuit
breaker) which disconnects power to the heater in the event
necessary for service diagnosis.
ent leak to ground exceeding the adjustable
be manually reset.
of overcurrent, high temperature, or low water level; breaker
must be manually reset.
GROUND FAULT DETECTOR – A device to provide a warning
signal if there is current leak to ground exceeding the
adjustable set point.
ALARMS – Horns, bells, or lights may be furnished to display or
warn of any condition for which sensors have been specifi ed
METERS – Any of the following meter
s can be furnished
mounted on the boiler or in a panel for remote mounting:
Voltmeter, Ammeter,
GOLDENROD
®
Watthourmeter.
ELEMENTS - Available with Optional Goldenrod
Elements. All NW models are available with the Goldenrod 24K
gold plated elements (patent pending). Goldenrod Elements
provide long-life and fi ve times the scaling resistance of
standard incoloy elements. Goldenrod Elements carry a threeyear warranty against failure due to scale.
OPTIONAL TANK LINING (NON-POTABLE SERVICE)
GLASS LINED TANK – All internal surfaces of the vessel
exposed to water shall be glass lined with an alkaline
borosilicate composition that has been fused-to-steel by fi ring
at a temperature range of 1400°F to 1600°F. This glass was
specially developed for use in water heaters. Consult factory for
operating temperature range.
EPOXY LINED TANK – A solventless two component epoxy
lining applied to a minimum 10-mill (0.010”) dry thickness.
Available on NW-150 and larger tanks. Consult factory for
operating temperature range.
SUGGESTED SPECIFICATION
Electric hot water boiler system shall be A. O. Smith Dura-Power™model number NW_____ with _____gallons capacity ASME “H” code for _____ psi
working pressure. The boiler will be complete with 3” of fi ber glass insulation, 18 gauge steel jacket and control cabinet. Trim to consist of CSA Certifi ed
and ASME Rated T&P relief valve. Boiler system will be complete with ____kilowatt incoloy sheathed heating elements with prewired 24” terminal leads.
Each element shall be easily replaced by removing 4 bolts. Boiler output to be _____BTH or _____kW at _____V, 3 phase, _____Hertz (cycl
elements to be switched by 50 ampere magnetic contactors with a minimum duty rating of 100,00 cycles at full load. Each contactor and heating element
circuit is protected by fusing with a minimum of 100,000 ampere interrupting capacity. Control circuit for energizing and magnetic contactor coils shall
be 120V with one side grounded, obtained through a control circuit transformer which is fused on both input legs and the ungrounded output leg. The
control circuit shall have the following additional items: on-off pilot switch, pilot light, 2 hig
solidstate
the heating demand (90kW and above). This control will time delay each stage and progressively add orsubtract stages as required by the temperature
sensor. This control shall not allow more than one stage to be switch on atone time. The control shall have even load p
utilizes the “fi rst-on, fi rst-off” principle, thereby equalizing the ope
automatic recycle function will occur. The boiler wiring will be prewired to solderless terminal lugs for fi eld electrical connection. The entire boiler
system shall be factory tested and bear the Underwriter’s Label Service label for UL standard 834.
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step control. The operating control shall consist of a solid state modulating step control which will switch and balance the power input to
rating time of the heating elements and contactors. In case of power failure,
For Technical Information and Automated Fax Service, call 800-527-1953. A. O. Smith Corporation reserves the right to make product changes or improvements without prior notice.
h temperature limit controls, electric low water cutoff and
rogressive sequencing, which
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es). Heating
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