Heat Strip - Electric Auxiliary Heat Element Guide

A heat strip is an electric resistance heating element installed in an air handler or electric furnace to warm supply air.

What It Is

Heat strips convert electricity directly into heat as air passes across the energized elements. In residential HVAC they are often used as auxiliary or emergency heat with a heat pump, or as the primary heat source in an electric furnace or air handler.

These elements are simple in concept but draw significant electrical load. Sequencers, relays, limits, and airflow all matter because heat strips depend on the blower moving enough air to carry the heat away safely.

Types

Common versions include electric heat kits for air handlers, staged auxiliary heat strips, and electric furnace element banks with multiple circuits. Capacity is usually discussed in kilowatts rather than in gas furnace input terms.

Where It Is Used

Heat strips are used inside heat-pump air handlers, electric furnaces, and some package HVAC units. They are usually hidden behind service panels and controlled by the thermostat and unit control board.

How to Identify One

Homeowners usually identify heat strips indirectly through thermostat labels such as auxiliary heat or emergency heat, or by the equipment nameplate showing electric heat kit capacity. Signs of trouble include no backup heat, high power draw without warm air, burnt odor, or repeated breaker trips.

Replacement

Replacement is needed when elements burn open, terminals overheat, sequencers fail, or a heat kit no longer stages properly. Because the repair involves high-voltage circuits and HVAC safeties, replacement is normally an HVAC or electrical service job.

Heat Strip — FAQ

What is the difference between heat strips and a heat pump?

A heat pump moves heat, while heat strips create heat directly from electricity. Heat strips are less efficient but useful as backup or emergency heat when the heat pump cannot keep up.

Why is my thermostat showing auxiliary heat?

That usually means the system has turned on the heat strips to help the heat pump reach the set temperature. It often happens during very cold weather, defrost cycles, or when the thermostat is raised quickly.

Are heat strips expensive to run?

Usually yes compared with standard heat-pump operation, because electric resistance heat uses a lot of power. Short backup operation is normal, but heavy dependence on strips can push energy bills up quickly.

How do I know if a heat strip has failed?

Weak backup heat, a system that cannot hold temperature in cold weather, breaker trips, or an air handler that runs without expected temperature rise are common clues. Diagnosis usually requires electrical testing inside the unit.