Combined Heating and Hot Water Systems in Dorset

When designing a heating and hot water system, it is first very important to calculate the heat losses from the building and the demand for hot water. Insulation levels in new properties are now designed to much higher standards which in turn lowers the heating requirements and hence the carbon footprint of the building. It is often possible to upgrade the thermal insulation of existing properties which is the first port of call when considering a new heating system. 

A traditional heating and hot water system has always been designed with the calculation for the boiler size being based on the worst case scenario. That is, full demand on the system with an outside air temperature of minus 2 degrees centigrade. However, these conditions only prevail on perhaps only 8 days a year and for the rest of the time a large capacity boiler is not working efficiently.

Combined heating and hot water systems involve using two or more different heat sources, using the lowest carbon source first and gradually adding heat until the total required output is obtained.

For example, solar thermal panels can provide most of the domestic hot water requirement for a family home throughout the summer months with barely a sign of a carbon footprint. These panels may produce 3 kWs or more and even contribute to the whole heating system throughout the remainder of the year.

If a wood burning stove with back boiler is added to the system, this can contribute perhaps another 12 kWs which again is carbon neutral and would probably provide sufficient heat for most of the year.

In times of severe weather or when the stove is not lit, then perhaps the system can be backed up with an air source heat pump or condensing gas or oil boiler. An air source heat pump is an extremely efficient way of producing hot water for both domestic use and central heating.

As from April 2011, the Renewable Heat Incentives (RHI) should be introduced and it currently looks as though a rebate of 7.5pence per kW of heat produced will be available for an air or ground source heat pump. The proposed RHI for a solar thermal panel is likely to be around 18pence per kW of heat.

Obviously, a condensing gas or oil boiler will not be eligible for RHI but with up to 94% efficiency, push button convenience and limited use, they may prove valuable to the overall system design.

All these combined heating inputs can be teamed up with both radiator or under-floor heating systems and various designs of hot water storage. Control of the system is of the utmost importance to gain the maximum efficiency and lowest carbon footprint. Addition of weather compensation to the controls adds a further sophistication.

Here at Low Carbon Energy Centre in Dorset we analyse the requirements of both the Client and the property and design a bespoke system to accurately suit their needs. The installation will not only reduce the carbon footprint of the property but also save money, add comfort and provide sustainability of supply for the years ahead.