How Are Finned Tubular Heaters Used as Auxiliary Heaters in Heat Pump Systems?

Heat pumps are becoming an important solution for building electrification because they can provide heating with much lower electricity consumption than conventional electric resistance heating. However, a heat pump does not always provide enough heating capacity under every operating condition.

This is where auxiliary electric heating can be used.

Finned tubular heaters are one option for providing supplemental heat in forced-air heat pump systems, particularly when additional heat is required during cold-weather operation, defrost, or peak heating demand.

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An air-source heat pump extracts heat from outdoor air. As outdoor temperatures fall, the available heating capacity and efficiency of the heat pump generally decrease, while the building's heating demand increases.

The U.S. Department of Energy notes that cold climates may require specially designed heat pumps before the system switches to resistance heating.

There is another challenge: defrosting.

During heating operation, frost can accumulate on the outdoor coil. The heat pump periodically enters a defrost cycle to remove it. DOE identifies defrost operation as one situation in which backup electric resistance heating may be needed to offset temporary cooling effects.

Therefore, auxiliary heating is generally not intended to replace the heat pump.

Its role is to provide additional heat when the heat pump alone cannot efficiently meet the required heating load.

A typical forced-air arrangement can be understood as:

Heat Pump → Airflow → Finned Tubular Heater → Warm Air → Conditioned Space

The heat pump provides the primary heating. When the control system determines that additional heat is required, the electric heater is energized.

The tubular element converts electrical energy into heat. Metal fins attached to the tube increase the heat-transfer surface area, allowing heat to be transferred more effectively to moving air.

Finned tubular heaters are specifically designed for forced-air applications because the fins increase the available heat-transfer area. JAYE's technical catalog also notes that, under the same watt density and air-stream conditions, finned tubular heaters can operate at a lower surface temperature than regular tubular heaters.

Depending on the system design, finned tubular heaters may be installed in:

Air handlers
Duct heating sections
Fan coil units
Heat pump indoor units
Make-up air systems
Commercial HVAC equipment

The heater may be configured as a single element or as a bank of multiple elements to provide staged heating.

For example, DOE documentation recognizes electric resistance heating as a possible supplemental heat source in air-source heat pump systems, while commercial HVAC designs may integrate resistance heating into air-handling equipment.

The fins increase the external surface area available for air-to-metal heat transfer.

This makes the finned tubular design particularly suitable for moving air, where efficient heat transfer is important.

More heat-transfer area can be provided within a relatively compact heater section. This is useful when an auxiliary heater must fit inside an air handler or duct.

Multiple elements can be arranged into heating stages, allowing the system controls to activate only the required amount of auxiliary heat.

Unlike exposed resistance wire, the resistance element is enclosed inside a metal tube. This provides a mechanically robust heating structure for HVAC and industrial air-heating applications.

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