Setting up and balancing the central heating system has been updated by Practical Home Energy Saving plus more on setting thermostats plus more information added to the boiler types page. Balancing the central heating system means obtaining similar temperature drops across all radiators, i.e. they all have a good flow through them. Ideally each radiator will have a thermostatic valve (adjustable by a knob) at one end and a flow regulating valve (also known as a lock shield valve) at the other (usually covered by a cap). Often there will be one radiator without a thermostatic valve (usually in the bathroom). The objective is to get the temperature drop across all radiators to be about 12 degrees Centigrade (20 degrees Fahrenheit). The hotter end of the radiator is the ‘flow’ and the cooler the ‘return’. If the pump flow rate is too high the temperature drop across the radiators will be less than 12C on a properly balanced system. Once a system has been balanced it should only need redoing if modifications (including improved insulation) or repairs are carried out. It is quite common to come across systems that have never been balanced or balanced very badly. Zone control valves are fitted to some systems to enable some areas of the house to be turned off or kept at a different temperature e.g. turn off the heating to the bedrooms during the day. Before trying to set up a central heating system make sure there are no faults, the radiator fault page gives more useful information.
After a fair few questions from readers we have added a page on boiler types to the heating section. There are three types of gas and oil central heating boilers which are described below. Modern boilers are all of the condensing type to maximise efficiency, typically these boilers when set up properly are over 90% efficient. Each has advantages and disadvantages which need to be taken into account when choosing a replacement boiler. All boiler types can be difficult to set up to maintain maximum efficiency i.e. condensing under all circumstances.
Condensing boilers work by recovering the waste heat which is expelled through the flue system of a non-condensing boiler and passing it through a second heat exchanger where it extracts additional heat. With a boilers that are 10 years old or more which don’t have the benefit of condensing technology, as much as 30% spent on fuel for heating and hot water is wasted. With a condensing boiler When the flue gases get so cool that the water vapour in the gas condenses out (hence the name) even more energy is recovered from the condensing vapour, and the boiler efficiency is maximised. Whether the boiler condenses is affected by the temperature of the water returning to the boiler from the heating system which needs to be below approximately 55C for condensation to occur. By combining a new condensing boiler with intelligent heating controls the whole system can be made highly efficient.
Practical Home Energy Saving has added info on programmable valves to the thermostatic radiator valve (TRV) page. Often referred to as TRVs the purpose of thermostatic radiator valves is to enable control of the temperature in individual rooms, turning off the hot water flow when the room reaches the set temperature. If radiators are not fitted with these there is considerable scope to improve the efficiency of the heating system by fitting them. Unless there is a bypass system one radiator, usually the bathroom, should not be fitted with one otherwise when all rooms reach their set temperature the pump will be trying to force water through a blocked system.