In a heat pump using electric resistance auxiliary heat, where must the indoor refrigerant coil be positioned in relation to the electric heating coil?

For a heat pump utilizing electric resistance auxiliary heat, the indoor refrigerant coil must be positioned before the electric heating coil in the airflow sequence. This arrangement is essential to ensure effective heating and energy efficiency.

When the heat pump is operating normally, it extracts heat from the outside air and transfers it to the indoor space via the refrigerant coil. However, during particularly cold conditions, when the heat pump cannot provide sufficient warmth on its own, the electric resistance auxiliary heat kicks in. Placing the indoor refrigerant coil before the electric heating coil allows the system to first transfer any heat it can gather from outside. If the heat pump requires assistance to meet the desired indoor temperature, the electric heating coil then provides additional heat.

This sequence helps to maximize the efficiency of the system, as the heat pump can do most of the work when conditions allow, while the electric resistance heat serves as a supplemental source only when necessary. Hence, positioning the refrigerant coil before the electric heating ensures that the system primarily relies on the more energy-efficient heat pump operation before resorting to the less efficient auxiliary heating method.