Electric Duct Mounted Heaters for HVAC System

This article describes the minimum requirements for electric duct mounted heaters. Duct heaters shall have components mounted and wired at the factory and terminated at terminal board for field connection.

Electric Duct Mounted Heaters for HVAC System

Electric Duct Mounted Heaters for HVAC System

Electric Duct Mounted Heaters for HVAC System


Product data shall include rated capacities; shipping, installed, and operating weights; furnished specialties; and accessories for each model indicated.

Shop Drawings:

    • Wiring diagrams indicating power, signal and control wiring. Wiring diagrams shall differentiate between manufacturer installed and field installed wiring.
    • Access requirements around other work, including working clearances to mechanical controls and electrical equipment.

Operation and maintenance data shall be submitted for duct mounted heaters to include operation and maintenance manuals.

Quality Assurance

Electrical components, devices, and accessories shall be listed and labeled as defined in NFPA 70, Article 100, by a testing agency acceptable to authorities having jurisdiction, and marked for intended use.

Heating Elements

  • Heating elements shall be finned tubular consisting of 80 percent nickel, 20 percent chromi
  • Heating elements shall be insulated and precisely centered in a steel tube filled with magnesium oxid
  • The entire heating element assembly shall be compac
  • The tube shall be insulated for operation up to 600 volts.
  • A corrugated copper plated steel fin shall be wrapped around the tube to increase the heat transfer surfac


Frames shall be slip-in or flanged as required by duct construction, constructed of aluminized steel.

Over Temperature Protection

  • Heater shall be provided with triple overheat protectio
  • Disc type automatic reset thermal cutoff shall be provided for primary over temperature protection.
  • Disc type, lead crossing manual reset thermal cutouts, factory wired in series with heater stages shall be provided for secondary protection.
  • Air flow switches shall de-energize heaters on loss of airflow.


  • Heaters shall be rated for the voltage, phase and number of stages required by the specific project.
  • Three phase heaters shall have equally balanced three phase stages.
  • Internal wiring shall be suitable for 105 °C.


Heaters shall be furnished with insulated terminal box, thermal cutouts, differential pressure airflow switch, disconnect switch, fuses, control circuit transformer 480V/120V with fused primary, interlocking heater door disconnect switch.

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