The design for Econostor II was born out of the development of what is known as the dual-tank principle and this technology in simple terms utilises a neutral primary fluid between an outer tank and inner tank indirectly heating the water within the inner tank for secondary hot water usage. The neutral fluid is heated by way of the combustion chamber and flue ways and this fluid can also be utilised for the purposes of providing heating. Therefore, the Econostor II can serve a dual purpose of not only a hot water service generator, but can also provide heating. The unit would ideally suit those commercial properties where the heating load is relatively low in relation to the hot water service load and space is of a premium. However, the unit can be utilised extensively for hot water service generation only.