The central water heater tank is a heat exchanger storage tank that is used to heat up the desired liquid.
It’s called a calorifier tank when the source of heat is another liquid generated from boilers, solar system, etc.
And it’s called an electrical water heater tank if the source of heat is the electricity (electrical resistances).

These centralized water heater tanks can be supplied in several types:

• Water Heater Tank with Single Serpentine Type (Or called with Fixed Internal Heat Exchanger).
• Water Heater Tank with Double Serpentine Type (Or called with Two Fixed Internal Heat Exchangers).
• Water Heater Tank with Tube Coil.
• Electrical Heater Type.

Electrical type can be combined with other types as backup power