System schematic of an open vented system with an oil boiler and a solid fuel stove, two central heating zones and a domestic hot water (DHW) cylinder. There is also a heat leak radiator on the gravity fed circuit of the solid fuel stove to prevent overheating when the stove is burning.
There is also a lever valve between the heat leak radiators and one of the heating zones. The valve can be opened so that the heat leak radiator can be heated from the oil boiler when the solid fuel stove is not burning.
The NRG Zone 4 manifold ensures that the boiler receives the coldest possible return water so that it is working under optimum conditions and with optimal efficiency. This is especially important for condensing boilers as it greatly increases the likelihood of the boiler operating in condensing mode, which is by far the most efficient. The manifold also ensures that the central heating zones and the DHW cylinder have access to the warmest possible water for their flow. The manifold also provides the system with a full bypass, meaning that the boiler can always maintain its optimal flowrate.
At the same time, it allows any unused heat from the boiler to have a direct bypass back to the Solid Fuel appliance to minimise condensation in the Solid Fuel appliance. This is beneficial since condensation in the solid fuel appliance can lead to corrosion in the appliance.