Watlow Duct Heater LDH Modular Series

  • LDH Series & D Series
  • D Series accepts an optional Type J or K Thermocouple
  • MDH Series: Modular heating elements
  • Approvals: UL and CSA
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Watlow duct heaters consist of WATROD heating elements that mount to a 1⁄4 in. (6 mm) thick steel flange. The heater is easily adaptable to many non-pressurized air heating systems and is simple to install. Also these air duct heaters support a wide range of applications requiring vast changes in temperature versus air flow combinations. Additionally the Watlow module duct heater increases reliability while offering accessibility without needing to pull the complete heater from the ductwork. The benefit is reducing downtime costs because each heating element is replaceable individually.  Overall the performance improvements include faster response time and reduce infiltration from the air stream heat into the electrical enclosure.

Also Watlow duct heaters have added benefits over oil or gas air duct heaters in a number of ways.  Benefits include installation flexibility, zero fuel lines, energy efficiency, universal availability of electricity, resistance coil in sheath is protected from corrosive environments, duct heaters with general purpose enclosures meet UL® and CSA component recognition to 480 and 600VAC maximum respectively, and finally UL® and CSA file numbers are E52951 and 31388.

Additionally, Watlow modular duct heaters have a reliable design with individual modules that are removeable through the enclosure of the assembly. Therefore the need of completely removing the heater from the duct work is eliminated and downtime is reduced.

See parts numbers and more specifications in our Technical Documentation.

Watlow Duct Heater Series

The Watlow LDH Series Air Duct Heaters have welded alloy 840 WATROD elements.

These duct heaters are for High Temperature Air 800°F (427°C), and Medium Temperature Air 750°F (399°C) applications. They all have welded alloy 840 WATROD elements, without thermostat, general purpose enclosure and steel flange. 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) 1-1/2 inch NPT conduit openings; 21 element (B = 20-1/4 in.) heaters have (2) 1-1/2 inch NPT conduit openings; remaining 21 and 24 element heaters have (3) 1-1/2 inch NPT conduit openings. All flanges are 12 inches wide.

The Watlow D Series Air Duct Heaters have removable alloy 840 WATROD elements, and have an option to use a thermocouple for temperature sensing.

Thermocouples Type J or K thermocouples, inserted in the thermowell, accurately sense element sheath temperature for over-temperature conditions. In addition, to sense process temperature, the sensing element should be located downstream from the duct heater. This will eliminate incorrect sensing caused by radiant heat. Thermocouples are supplied with 120 in. (3050 mm) leads, longer lead lengths are available – this applies to Watlow Air Heater D Series only. In summary, the duct heater D series thermowell holds thermocouple for sensing sheath temperature.

The Watlow Modular Air Duct Heaters offer quality performance and increased versatility to low temperature applications. The modular duct heater consist of two parts, first is a six kilowatt heater available in 240 or 480 volts, single or three-phase. The second part included on this heater is the electrical housing that protects each modular termination area. Furthermore the range of modular accommodations is from one to 10 elements and a range from six to 60 kilowatts, in increments of 6 kW.

Typical Applications

  • Drying ovens
  • Autoclaves
  • Furnaces
  • Load bank
  • Heat treating
  • Reheating
  • HVAC
  • Paint drying

We provide engineering and product support for your application.

Technical Documentation

Download PDF Files:

Watlow Duct Heater Catalog

Watlow Duct Heater Specifications

Watlow Module Duct Heater Specifications

Watlow Duct Heater Installation and Manual