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 are also two heat leak radiators on the gravity fed circuit of the solid fuel stove to prevent overheating when the stove is burning.
There is also a motorized valve between the heat leak radiators and one of the heating zones. This is a normally open valve and it will stay open if there is a power outage or if the overheat thermostat tells it to. The valve ensures that the solid fuel stove has access to all the radiators of heating zone 2 to prevent overheating if the heat leak radiators are unable to dissipate all the heat.
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.