Features:
1) Uses a copper coil as the heat exchanger inside the tank, rather
than water
2) The storage tank acts as a thermal source
3) Mains pressure cold water flows directly through the copper coil
making it hot

Picture Key:
1) Storage Tank Fill
2) Heat Exchanger Mains Cold In
3) Thermal Source
4) Copper Coil As Heat Exchanger
5) Vent
6) Heat Exchanger Hot Out