Cylinder Types
Directly Heated
In this system the water drawn from the storage cylinder has passed directly through the heat exchanger of the appliance.
Indirectly Heated
In an indirect system (see figure) the stored water is heated by a calorifier (heat exchanger) within the storage cylinder. This calorifier can be either a coil type or an immersion type(as shown further down).
Cold water storage tank
Circulator
Hot Taps
Direct Cylinder
Circulator
Cold water storage tank (for hot water)
Cold water storage tank (for central heating)
Indirect Cylinder
Coil Inside Cylinder
Hot Taps
Direct System
Cold Feed (from cold water storage tank)
Vent Pipe(going to cold water storage tank)
To draw off points i.e hot taps
Primary Flow From Boiler
Primary Return To Boiler
Coil Type
Indirect System
ImmersionType
Vent Pipe(going to cold water storage tank)
To draw off points i.e hot taps
Cold Feed (from cold water storage tank)
Primary Flow
Return
Vent pipes
Vent pipe
The heat exchanger is connected by flow and return pipes to the heating appliance and there is no direct contact between the water in the appliance and the water drawn from the taps. This sytem is particularly suitable in hard water areas, as water circulating through the heat exchanger is not continually replaced with fresh, thus minimisng formation of scale.
