System schematic of an open vented system with two solid fuel appliances, two radiator zones and a domestic hot water (DHW) cylinder.
The two solid fuel applainces use the DHW cylinder as a common DHW heat leak circuit.
The returns to the appliances show optional piping methods.
The cooker on the right will draw from the coolest zone return water and the stove on the left will have better access to the warmer bypassing water.
The NRGZone 4 manifold ensures that the central heating zones and the DHW cylinder has access to the warmest possible water for their flow.