Heating, Cooling and HVAC

Heat pump systems are known as one of the most efficient methods of heating and cooling. Using an ETS unit to provide the supplemental heat needed with a heat pump at low outdoor temperatures instead of the more commonly used direct electric strip heat allows the heat pump’s high efficiency to be combined with the advantage of off-peak electric rates.

In heat pump applications, the ETS unit replaces the resistance strip heat or other back-up heat, with low-cost, off-peak stored heat. As outside temperatures drop, the stored heat in the ETS unit is used in conjunction with the heat pump’s heating capacity to satisfy comfort requirements. During on-peak hours or when the demand for heat is at the point where the heat pump alone cannot satisfy the heating requirements, the stored heat is used to supplement the heat pump. Using an ETS unit allows the heat pump’s high efficiency to be used even during times of cooler outdoor temperatures.

The Heat Pump/ETS system benefits:

Provides comfort 24 hours a day
Provides for a high efficiency, low cost heating and cooling system
Optimizes system performance by allowing the heat pump’s efficiency to be fully utilized
Eliminates the cool discharge air temperatures associated with older model heat pump systems during times of low outdoor temperatures.
The heat pump/ETS combination, when used with off-peak electric rates, is a more economical heating system than a heat pump with electric strip heat.

How the System Works

1.The room thermostat in the home is set to desired comfort level. If room temperature decreases below the room thermostat set point, the system is energized to deliver heat.

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 ETS 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 ETS unit’s core blower will modulate low cost, off-peak stored heat into the duct stream so comfortable heat (generally 90° F or higher) can be delivered into the home. In the diagram, the conditioned air is shown at 95° F.

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.

Source:Home Energy Library