ETS How the System Works


  2. Upon a heat call from the room thermostat, the heat pump's outdoor compressor unit is energized and warms the refrigerant coil in the heat pump unit. At the same time, the Electric Thermal Storage unit's supply-side blower is energized.

  3. The supply-side blower draws air from the home (shown at 68° F) across the air filter and the heat pump's refrigerant coil, extracting heat from the coil as it passes through.

  4. A sensor monitors the temperature of the air as it leaves the coil. If the air temperature is warm enough to be comfortable for people in the space, generally 90° F or higher, the supply air blower simply delivers the warm heat into the home through the supply air duct. Air temperature after passing over the coil in the diagram is shown at 85° F.

  5. If air temperature after the heat pump coil is below a comfortable level (generally less than 90° F), the system will call for back up heat, better known as auxiliary heat.

Because heat pumps generally have an operating efficiency of 150 to 300 percent (depending mostly on outdoor temperature), the ETS system first uses the heating ability of the heat pump. If the heat pump doesn't have the ability to satisfy space heating requirements, the ETS system starts working with the heat pump, using low-cost, off-peak energy to provide comfort. Combining the heat pump's efficiency with the off-peak ETS system yields comfort at a low operating cost.