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TPI translated

Research commissioned by controls association BEAMA has found that using a Time Proportional Integral (TPI) thermostat together with thermostatic radiator valves (TRVs) was shown to reduce home energy costs by 53 per cent1.

This is a further 13 per cent reduction in running costs compared to the tests using a more conventional room thermostat. So what makes a TPI thermostat different to a conventional device?

Room thermostats have traditionally featured an on/off algorithm, which in basic terms means that the heating will switch on when a room is below the thermostat’s setting, and the heating will switch off when the temperature goes above the setting.  

The majority of older room thermostats feature this type of functionality, however it is not the most effective when it comes to maximising homeowner comfort and keeping energy usage to a minimum.

This is because the room temperature is effectively fluctuating around the target temperature set on the thermostat, which will result in wasted energy. Another consequence may be that the temperature is not as consistent as it could be; meaning the comfort of the homeowner is not maintained.

What is TPI?

A number of modern and more advanced heating controls - such as room thermostats and programmable thermostats - feature Time Proportional Integral (TPI) control.

It is a proven method of minimising energy use by calculating the demand from a thermostat. Devices that boast TPI are able to ensure more accurate temperature control, and this results in both energy savings and increased comfort levels.

They feature a more complex algorithm, which constantly adapts to the conditions of the environment in order to estimate the correct steady state ratio of each room within six, ten-minute cycles per hour, when the Gas option is selected.

During each one of these ten-minute periods, the algorithm calculates the length of time the heating should be on for to maintain thermal equilibrium.

The ‘I’ (integral) part of the TPI control makes small, long-term adjustments to the process, varying the length of the heating times to keep the room temperature even more precisely on set-point.

Additional advantages

Furthermore, TPI room thermostats often allow for the overall temperature setting to be reduced, because they maintain the heat levels so efficiently.

This results in additional reductions in energy usage, which in turn will lower household heating bills. In fact, turning a heating system down by just one degree can actually reduce energy consumption by 10 per cent, so the savings that can be gained are significant.

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