Heating-system controls on trial

Published:  01 November, 2013

TACMA, control, TRV, room thermostat, University of Salford, space heating
The true effectiveness of heating controls — Colin Timmins.

Colin Timmins, director of TACMA, the controls association within BEAMA, explains how research has shown that potential energy savings from heating controls are very much larger than previously thought.

How do you reduce the energy used by space heating in homes? A pertinent question, given that space heating is usually the single biggest element of a home's energy use and is something that householders increasingly worry about, as shown by the now regular debate about how late in the year you can wait before turning on your heating system.

The application of building insulation and installation of a higher efficiency boiler are often talked about as the solutions to high heating costs. In many cases the application and use of heating controls, is almost seen as an afterthought. To address this, the controls association within BEAMA, TACMA, recently carried out some research to identify the technical potential for savings from heating controls alone.

The key finding from this research is that the installation of a room thermostat and thermostatic radiator valves (TRVs) onto a heating system can reduce the energy costs by more than 40% — far higher than currently estimated by the standard UK calculation methodology for energy saving measures (SAP).

Representative of over five million homes in the UK — the Energy House at the University of Salford.

The research was based on independent testing by the University of Salford in its Energy House facility. This facility consists of a full-size house built within an environmental chamber. It is designed to monitor energy consumption before and after retrofit measures are installed so that the true effectiveness of new and existing technologies to reduce energy can be assessed. The house is representative of over five million of the current UK housing stock and is fully furnished and fitted as a typical working home with a conventional heating system with an A-rated condensing boiler and radiators.

Three tests were carried out with the environmental chamber maintaining an average winter external temperature of 5°C and with the heating system timed to come on and off in accordance with the SAP weekday heating pattern of two hours in the morning and seven hours in the afternoon/evening, both with a 30 minute warm-up time. The tests were as below.

• Test 1. The heating system was operated with no temperature control other that the internal boiler thermostat. The cost of running the system for 24 hours was £5.31.

• Test 2. The heating system was operated with temperature control by a room thermostat (with interlock) located in the living room. The cost of running the system for 24 hours was £4.68, 12% less than test 1.

• Test 3. The heating system was operated with temperature control by a room thermostat (with interlock) in the living room and TRVs on all radiators other than the one in the living room. The tests were conducted using TRVs with the ‘keymark’ which independently guarantees reliability and performance. The cost of running the system for 24 hours was £3.15, 41% less than test 1.

Graph 1: With no control other than the boiler’s own thermostat, the return temperature (red line) was a fairly steady 60°C, preventing condensation.

The scale of savings shown in these tests is significantly better than what is generally assumed, particularly for TRVs. The same house had an assessment carried out using the SAP methodology, which is the standard calculation tool used by Government in many of its policy tools such as the Green Deal. Under this tool the energy savings from the addition of TRVs is estimated at 2%, rather than the approximate 30% savings shown under the actual tests.

An interesting observation from the tests was the effect of controls on the boiler operation. The boiler used in the tests was a condensing boiler, as is typical of most boilers installed in the UK in recent years, which operate most efficiently when the return temperature is lower. In test 1, where the boiler was operating without any external temperature controls the return temperature remained fairly constant at around 60°C. [Graph 1]

However, by test 3 when the boiler is operating with temperature control by both a room thermostat and TRVs the return temperature has reduced to an average of around 50°C, even though the boiler thermostat setting was the same as in the first test. [Graph 2]

Graph 2: With the same boiler thermostat setting as in Fig. 1, the addition of a room thermostat and TRVs reduced the return temperature (red line) to an average of around 50°C — permitting condensing operation.

More analysis will be undertaken to look at the effects of the controls on the efficiency of the boiler, but the indications are that the controls are delivering more efficient operation as well as reducing the energy that the boiler needs to deliver by maintaining lower temperatures in rooms other than the main living area.

What is certainly clear is that these readily available controls can significantly improve comfort for householders by providing satisfactory heat distribution around a dwelling.

Other emerging research is showing how householders without adequate controls face a running battle to maintain comfortable temperatures with their system by, for example, by opening windows, manually operating radiator valves, or simply turning the boiler on or off — none of which are satisfactory from either a comfort or efficiency perspective.

It seems clear from this new evidence that the UK heat strategy should have, as a priority, a plan to address the millions of UK homes that currently don't have suitable control systems.

Colin Timmins is director of TACMA, the controls association within BEAMA. TACMA represents manufacturers and suppliers of electrical and electronic controls. Members are: Danfoss, Honeywell, Horstmann, Invensys, Myson, Pegler Yorkshire, Siemens, and Sunvic.

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