Regarding the internal refrigerant coil, the heating speed is very fast, much more convenience for customers use the hot water. Better protect the compressor.
However, the coils contact the water under high temp with long time, the coils will be easy to corrosion. For bad water quality area, we do not suggest customers choose internal refrigerant coil.
Internal refrigerant coil
External refrigerant coil
Regarding the external refrigerant coil, the coils do not contact the water directly. The coils are not that easy to corrosion or oxidation. more durable & do notaling. Make sure the water clean when using. But the heating speed is not that fast than internal refrigerant coil.
