operating conditions. Each heating element in the module shall be
capable of being operated at and shall be rated at 2690 watts per
square meter 250 watts per square foot, but shall be designed to
operate at 2152 watts per square meter 200 watts per square foot.
Size wiring, circuits, and controls for 2690 watts per square meter
250 watts per square foot. Total power density shall be not less
than 4303 watts per square meter 400 watts per square foot of
heater module surface. Construct heating elements of 600 series
stainless steel alloy or ni-chrome encased in a 20 gage minimum
thickness aluminum or aluminized-steel mounting pan or casing.
Provide two sets of heater pigtails for each module, one set of
pigtails for each element and circuit. Provide multistrand copper
pigtail and interconnecting wires with high temperature (454
degrees C850 degree F) insulation. Furnish heater pigtails with
strain relief constructed to prevent damage to the heater modules
due to rough handling. Provide pigtails of sufficient length to
reach the terminal box. Splices are not permitted in pigtails
from modules, tapes, or blankets to the terminal box. Perform
hopper heater module voltage tests for each module, blanket, or
tape for electrical integrity at 1,000 volts. Provide heating
modules with metal labels firmly attached to the module listing
the wattage and voltage of the module. Construct heating modules
and mounting hardware of high temperature materials capable of
withstanding 454 degrees C 850 degrees F. Insulate heating
modules with high temperature woven glass cloth or mineral fiber.
Mica or magnesium oxide insulated heaters are not acceptable.
b.
Hopper Heater Installation: Heater modules shall provide maximum
contact between the heaters and the hopper wall.
2.5.3.2
Hopper Heater Controls
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NOTE: Use these paragraphs for local control only.
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NOTE: Use these paragraphs for master control only.
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Control each hopper heater zone thermostatically with adjustable setpoint
and provide complete including power, control and alarm components. Provide
120 volt AC adjustable type thermostats for monitoring hopper temperature
and locate in NEMA ICS 6, Type 4 enclosures. For thermostatic control of
the hopper heater system, provide a Master Hopper Heater Control Panel for
each precipitator, a Local Hopper Heater Control Panel for each hopper, and
a Local Hopper Heater Zone Terminal Box for each zone. Provide materials,
tools, and labor required for connections of circuits and wiring between
local hopper heater zone terminal boxes, local hopper heater control
panels, and the master hopper heater control panels.
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NOTE: Use these paragraphs for local control only.
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a.
Local Hopper Heater Zone Terminal Box: Provide hot-dipped
galvanized NEMA ICS 6, Type 4 hopper heater terminal boxes with
terminal blocks for connection of heater pigtails and thermostat
leads on each hopper for each hopper zone. Provide a sufficient
SECTION 15862N
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