Central heating boilers have changed over the years to be far smaller, and yet more powerful. The demand for space in the house has put pressure on any item that can be removed without too much trouble. The removal of the hot and cold water tank, and the replacement with a combination boiler that provides heating and hot water directly from mains water supply on demand, has given a lot of extra space and far less piping.
The major problem is that the hot water supply from the combination boiler Geen warm water is limited, and to date has not been adequate when there are a large number of people in the house. One recent development is what the manufacturers call a Flow Smart system, where the hot water supply is dramatically increased by the addition of a small thermal store that is fitted just below the boiler. The space taken up is quite limited but the hot water supply increases enormously.
A typical combination boiler can deliver about 18 litres of water at a temperature of 50 to 65 degrees C for around 9 minutes, after which the temperature drops to about 40 degrees C. In a Flow Smart system when a 25 or 50 litre thermal store is added then the water temperature remains at 50 to 60 degrees C for over 30 minutes.
The system works by taking cold water from the mains and passing it through the boiler where the waste gases from the boiler preheat the cold water, and from there it passes through a coil in the thermal store where it is heated from hot water from the primary store. The water then flows into the boiler on demand at a temperature of 30 degrees C. The boiler can then heat this supply to 50 to 60 degrees C quite easily as the temperature rise is so much less, and therefore supply so much more hot water.
It is claimed that the system can supply equally as much as a 200 litre hot water tank at a far more efficient energy usage and in a lot less space. The thermal store can either be a 25 or 50 litre size depending on demand. Where small industrial units are supplied, the system has been ganged with 2 or more units rather than the giant boiler systems at a much cheaper cost. The system lends itself to the thermal store being heated by small solar panels.