System schematic of an open vented system with an oil boiler and a solid fuel stove as the heat source. The system has two central heating zones with radiators and a domestic hot water (DHW) cylinder.
The DHW cylinder is on the gravity fed circuit of the solid fuel stove and acts as the heat leak of the stove. Since the cylinder has two coils it can also be heated by the boiler when the solid fuel stove is not burning.
The NRG Zone 5 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 has 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 boilers 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.
With this solid fuel arrangement the stove’s heat is made available to the heating circuits in the NRGZone before it is allowed to pass through the primary heat leak DHW cylinder.
The temperature of the DHW then can be controlled by a combination of the pipe stat on the primary return to the stove and the DHW control stat on the cylinder which will allow excessive heat to be taken by the heating zones.
As with all solid fuel ‘drop systems’ it is critical to insulate the primary pipe work and the piping to the DHW Cylinder very well to minimise heat drift back out of the cylinder when the stove cools.
The Non Return Valve on the secondary DHW coil is also used to prevent any back circulation of the stored hot water from drifting back out of the cylinder to the system.