Why is it economic to use supplemental heat to “top off” the water temperature?
The EarthLinked system is capable of heating the water from its supply inlet temperatures (typically 10°C to 25°C up to 50°C) three times faster and at one quarter the cost of standard electric heating. When a compressor is called upon to deliver heat to water that is hotter than 50°C, there is greater resistance to heat transfer, so the compressor must work harder and use more electric energy. Although it may still be twice as efficient as standard resistance heating elements, it is necessary to avoid overloading the compressor. The remaining temperature rise is accomplished with supplemental heat, usually electric heating elements. Thus the EarthLinked system does most of the heating (69-77%) with high efficiency and the remainder is done with supplemental heat.
