Advice on Boiler Temperature Settings

With the cost of energy so high, there is little wonder that householders have become very conscious about fuel efficiency. With space heating accounting for around 65% of home energy fuel costs, any method of minimising energy wastage is likely to be welcomed by cash strapped families trying to make ends meet.

Heating technology has come a long way in the last 30 years. Compared with the old boilers they replace, new condensing boilers have managed to improve domestic boiler efficiency from below 75% to levels in excess of 90%. However, whilst domestic consumption has fallen as a result, gas prices have fluctuated considerably and although they have recently reduced slightly, the prospect of future rises remains quite likely.

Householders naturally seek to extract maximum efficiency from their expensive fuel. Many modern homes have been furnished with very sophisticated temperature monitoring and automatic heating control systems. However, opinions differ on what the correct boiler temperature setting should be. Turned up high or turned down low.

In the context of trying to establish what the correct boiler temperature setting should be, various factors come into play that can influence the improvement of efficiency, or the complete opposite.

For a modern condensing boiler, the return flow to the boiler must be below 55 degrees C for heat recovery by condensation to take place. If the return temperature exceeds this, the whole purpose behind installing a condensing boiler, and the benefit of reclaiming latent heat from the flue gases, is all but lost. Ideally, the return should be as low as possible, but not at the expense of inefficient space heating throughout the home.

There are a number of schools of thought on what might constitute the ideal boiler temperature setting. One view suggests that the introduction of two temperature gauges, one placed on the boiler flow outlet and the other on the flow return may provide the answer. These will allow an operator to manually correct the boiler temperature. By monitoring the return flow to ensure that its temperature does not exceed 55 degrees C. the operator can observe the outflow gauge to determine the hot water temperature required to support it. The operator can then adjust the boiler temperature settings accordingly.

A second method suggests that operating the boiler at its highest temperature setting continually will reduce gas usage by heating the home quickly to its required temperature and then the boiler will cycle on and off to maintain it.  The boiler will eventually settle down to deliver a return temperature of 55 degrees C. This system relies on the home having a full set of thermostatic controls and programmable settings. It also requires TRV’s on each radiator to turn off the heat supply to the radiator when the pre-set temperature is reached. Initially this results in the return flow to the boiler exceeding the 55 degrees C. required for condensing heat reclamation, so the boiler reduces its burner temperature automatically to reduce this in-balance. In combination with environment control programmers and timers, this method is purported to reduce overall gas consumption by quickly providing and then maintaining the household’s preferred temperature for pre-set periods, but only when required to do so.

A third school of thought would totally disagree and suggest an alternative method. They argue that setting the boiler temperature to a lower setting and running the central heating for much longer periods reduces gas usage. By operating the boiler at the lower temperature, the boiler does not cycle intermittently to boost heat levels, with the potential of overshooting heat requirement prior to room controls operating to reduce output. For this method to work efficiently, the radiators, or emitters must be of the larger capacity and size. Because of the lower output from the boiler, rooms take longer to heat up but expensive bursts of energy are not required to produce and maintain the heat. The condensing heat recovery is enhanced due to lower return temperatures. Heat exchangers in the boiler also tend to work more efficiently with lower temperatures.

Because this method relies on heating by a lower, longer heat supply, the boiler will need to operate continuously during cold weather to maintain internal temperatures and prevent condensation forming due to boiler inactivity caused by pre set programmers.

With this method of operation, the system must have a zone valve operation to provide domestic hot water priority. The domestic hot water must reach a minimum of 60 degrees C. to achieve protection from harmful microbial incubation and proliferation.

The final viewpoint on boiler temperature settings suggests that rather than concentrating on spending valuable time and money fiddling about with internal heating controls, homeowners might be better served by fitting a weather compensator. It probably goes without saying that the outside temperature variation has much more influence on internal temperature than delayed boiler activity to counteract its effects. By predicting the effect of cold weather on internal temperatures, and in combination with internal programmers, a weather compensator can activate a boiler earlier than would otherwise be the case. The boiler responds by gently raising output to compensate for expected heat loss from the building.

Many homeowners and their households enjoy a certain amount of control over their heating. This can be substantiated by observing the growing popularity of remote heating controls. For those who enjoy tinkering with heating controls to improve efficiency the matter of boiler temperature setting is subjective and a matter of opinion. Each home differs in the level of insulation, and indeed, the materials used in the build, and as such, each home will have specific requirements.

For those who simply want a comfortable home with the minimum energy cost, adhering to the guidance surrounding property insulation is essential.  The installation of suitable timers, thermostats and programmers and the addition of a weather compensator will override any contradictory advice relating to boiler temperature settings.

For simplicity and optimum efficiency, just leave it to the technology.