Constructed of sturdy 0.430 in. (11 mm) diameter WATROD™ heating elements mounted to a 1/4 in. (6 mm) thick steel flange, duct heaters are easily adapted to many non-pressurized air-heating systems. They are easily installed in applications requiring a wide range of temperature versus air flow combinations. The modular duct heater offers increased reliability. The individual modules are removable through the housing of the assembly, which eliminates the need to pull the complete heater from the duct work. This reduces downtime costs because the heating elements can be replaced individually. Performance...

Air HeatersDuct HeatersLDH SERIES and D SERIES English CFM measured at standard conditions FPM = - Duct cross section area at heater in ft2 Metric CMM measured at normal conditions MPM = Duct cross section area at heater in m2 Typical Applications • Drying ovens • Autoclaves • Furnaces • Load banks • Heat treating • Reheating • HVAC • Paint drying Choosing a Duct Heater The English and metric graphs, shown on the following pages, will help you to select the correct duct heater. These graphs include: Watt Density vs. Air Temperature/ Velocity, Watt Density vs. Sheath Temperature and Pressure Drop...

Air Heaters Duct Heaters LDH SERIES and D SERIES Watt Density vs. Air Temperature/Velocity curve’s intersecting point. This shows the recommended watt density based on a maximum sheath temperature of 1400°F (760°C). For longer heater life, lower watt densities should be chosen. WATROD Duct Heater Watt Density Vs. Air Temperature Velocity WATROD Duct Heater Watt Density Vs. Air Temperature Velocity To decide watt density requirements, first determine the desired outlet air temperature and velocity in feet per minute. Then, follow the lines on the graph for velocity and process temperature to the...

Air Heaters Duct Heaters LDH SERIES and D SERIES Pressure Drop vs. Air Velocity The rate at which pressure drops through the duct heater is critical for properly sizing blowers and pumps. The Pressure Drop vs. Air Velocity graph gives recommended maximum velocities in feet per minute and meters per minute according to the air velocity and duct heater size. To determine the pressure drop through the duct heater, follow the air velocity (FPM or MPM) over to the appropriate curve, which identifies the duct heater size. Then, take the intersecting point down to the approximate pressure drop value....

Duct Heaters LDH SERIES and D SERIES Options (Continued) Note: The WATCONNECT part number associated with a heater is only a suggestion. The following installation details need to be compared to panel capabilities to assure a compatible match: • Minimum and maximum ambient temperature where panel will be installed • Statutory and regulatory requirements at installation site • Sun loading, if any, at installation site • Presence of any hazardous gases, dusts or fibers, if any • Verification of process sensor type • Verification of limit sensor type • Input/Output (I/O) requirements For additional...

Extended Capabilities for Duct Heaters Extended \ qapabiltp(/ Performance Capabilities • Wattages to 2.2 megawatts Features and Benefits Ceramic fiber insulation available • Keeps wiring cooler and reduces heat loss Greater than 1/4 in. (6 mm) with 304 or 316 stainless steel flange material • Easily bolts to the duct wall 60 plus element designs available • Meets a wide variety of kilowatt demands Options Sheath Material Watlow duct heaters can be made with the following sheath materials: • 304, 316, 321 SS • Alloy 800 • Laminated alloy 600 (hi-temp) • Hastelloy C276 Contact your Watlow representative...

Air Heaters Duct Heaters Application: High Temperature Air 800°F (427°C) • Welded alloy 840 WATROD elements • Without thermostat • General purpose enclosure • Steel flange 1 3 and 6 element heaters have (1) 1 inch NPT conduit opening; 9, 12 and 15 element heaters have (2) 1 inch NPT conduit openings; 18 element heaters have (2) 11/2 inch NPT conduit openings; 21 element (B= 201/4 in.) heaters have (2) 11/2 inch NPT conduit openings; remaining 21 and 24 element heaters have (3) 11/2 inch NPT conduit openings 2 All flanges are 12 inches wide Part Number Notes: • See Watt Density vs. Air Temperature/Velocity...

Air Heaters Duct Heaters LDH SERIES Application: Medium Temperature Air 750°F (399°C) • Welded alloy 840 WATROD elements • Without thermostat • General purpose enclosure • Steel flange 1 3 and 6 element heaters have (1) 1 inch NPT conduit opening; 9, 12 and 15 element heaters have (2) 1 inch NPT conduit openings; 18 element heaters have (2) 11/2 inch NPT conduit openings; 21 element (B= 201/4 in.) heaters have (2) 11/2 inch NPT conduit openings; remaining 21 and 24 element heaters have (3) 11/2 inch NPT conduit openings 2 All flanges are 12 inches wide Notes: • See Watt Density vs. Air Temperature/Velocity...

Air Heaters Duct Heaters D SERIES Application: High Temperature Air 800°F (427°C) • Removable alloy 840 WATROD elements • Without thermostat • General purpose enclosure • Steel flange 1 6 and 12 element heaters have (1) 1 inch NPT conduit opening; 18, 24, 30 and 42 element heaters have (2) 1 inch NPT conduit openings; 36, 48, 54 and 60 element heaters have (2) 1 inch NPT and (2) 11/4 inch conduit openings 2 All flanges are 12 inches wide # of # Part WATCONNECT P/N Ship Wt. Elem. Volts kW Ph Circ Number J T/C K T/C lbs. (kg) 20 W/in2 (3.1 W/cm2) CONTINUED Notes: • See Watt Density vs. Air Temperature/Velocity...

Duct HeatersD SERIES Application: High Temperature Air 800°F (427°C) • Removable alloy 840 WATROD elements • Without thermostat • General purpose enclosure • Steel flange 1 6 and 12 element heaters have (1) 1 inch NPT conduit opening; 18, 24, 30 and 42 element heaters have (2) 1 inch NPT conduit openings; 36, 48, 54, and 60 element heaters have (2) 1 inch NPT and (2) 11/4 inch conduit openings ® All flanges are 12 inches wide Notes: • See Watt Density vs. Air Temperature/Velocity charts on page 379 to C/F - Contact factory, go to www.watlow.com/en/contact-us confirm suitability in the application....