Where should the electric backup heating system be located in relation to the indoor coil of a heat pump?

The correct placement of the electric backup heating system is downstream of the indoor coil of a heat pump. This configuration is essential because it ensures that the warm air produced by the backup heater is delivered to the living space after the air has passed through the indoor coil. If the air is first heated by the heat pump, which is typically the primary heat source, it can then utilize the electric backup heating system to further elevate the temperature when necessary, particularly during colder weather or when the heat pump's efficiency decreases.

Placing the backup heating system downstream allows it to effectively supplement the heat generated by the heat pump, ensuring a consistent and comfortable indoor environment. This arrangement also plays a vital role in system efficiency, as it prevents unnecessary operation of the electric heat and promotes the use of the heat pump as the first line of heating defense.

In contrast, locating the electric backup system upstream would directly cause it to heat air before it even passes through the heat pump coil, potentially leading to inefficiencies, as the heat pump could have to work harder than necessary. This strategic placement is vital for optimizing the heating performance and energy efficiency of the entire system.