Comfort and Convenience is put first Users may expect an annual saving of at least 25% on fuel consumption A proven track record
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Building Research Establishment Investigation

Summary of Findings

The DCD Domestic Heating Controller has been investigated by the Building Research Establishment, an Executive Agency of the Department of the Environment, and it is with their permission that the Overall Summary of their findings is reproduced below.

The DCD heating controller is a purpose built full featured unit aimed at the domestic housing market for the control of central heating and hot water. It offers ten discrete heating programmes for each day of the week for central heating and hot water, together with additional features such as optimum start, temperature smoothing, boiler cycling control and pump overrun.

In the simplest type of installation, the controller may be used to replace a time clock but, at BRE, a house was set up with a full installation comprising; the main controller, and sensors for room, hot water and external temperature. The investigations were carried out in two traditionally constructed detached houses, built with insulation standard just beyond current building regulations and equipped with modern well controlled heating systems. Both houses were equipped with simulated occupancy, which is programmed to provide the incidental gains from a "four person" household. The main points that emerged from the investigations were:

• An annual saving of some 25% on fuel consumption may be expected.
  

• DCDs Smoothing is capable of maintaining a central heating temperature differential of 0.1C, as against 0.8C for a standard system. Furthermore, its pump overrun and boiler cycling controls, ensure that radiators are warmed evenly and that there is a more even distribution of heating throughout the house that provides a greater degree of comfort.
  

• The Optimum Start, or warm to temperature, facility is effective. It saves fuel by switching on later on warmer days in the Spring and Autumn, and keeps the house occupants warmer on cold days by switching on earlier.
  

• The combination of features provided by DCD are not provided by other domestic control systems in a single package. Furthermore, all the controller's features were found to work satisfactorily.
  

• DCD puts comfort and convenience first, and the controller reacts quickly to sudden changes in conditions. While boiler cycling is regulated to obtain fuel economies and to minimise maintenance costs, the controller does not restrict boiler output in order to obtain fuel economies at times that the full power of the boiler is needed to maintain maximum comfort
  

The tests demonstrated that the DCD controller is a capable unit with the ability to manage domestic heating and hot water services to a high standard and provide substantial energy savings. It has many features and can accommodate a wide range of user options in both installation and operation. Reducing temperature will always save energy but, with the flexibility of the DCD controller, warmth can always be provided when it is required. Bottom line cost saving will depend upon the way the user wants to run their heating system but, with the DCD controller, features such as optimum start, temperature smoothing and pump overrun can offer improved system management whatever the desired temperature requirements.

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Features

General Description

The controller offers up to ten discrete heating programmes a day for each day of week, for water and for central heating, with optimum start and central heating temperature smoothing. It therefore provides great flexibility in programming requirements for maximum comfort at minimum fuel cost, and avoids the overheating of rooms beyond the temperature required.

The controller comes supplied with a room sensor, a water sensor and an outside sensor to provide the full benefits of its facilities. It may be unpacked from its box, connected up and, after setting the correct day of week and time, left running with standard factory set heating programmes. It builds up its history of operating experience, on a daily basis, which it uses to progressively improve its heating optimisation performance.

Once the controller is in operation, easily identified keys enable the majority of requirements for temporary changes to be made. The Boost key provides water heating to order, at times when no water heating programme is in operation, the Heating Programme Override key provides manual control of central heating when needed, and further keys allow temporary programme changes to be made for time and temperature. Naturally, once initial experience has been gained, the user may enter his own heating programmes and temperature settings in place of the factory settings.

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Simple to Use and Operate The diagram of the front panel illustrates the straightforward design with the simple and easy to use controls. Return to Contents of Page

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Simple for the Installer Besides being simple to use from the point of view of the user, the Controller is simple to install. Note that there is no crossover wiring and that the connections for the sensors may be made with low voltage cabling, such as bell wire or telephone cable. Direct connections may be made when separate central heating and water control valves are installed, also when two pumps (including dual pumps) are used. Return to Contents of Page

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Standard Programmes for Central Heating and Water Heating

The controller allows for a maximum of ten programmes to be set for each day of the week, making a total of seventy programmes in all. Each programme may contain different settings for central heating and for water heating and each will optimise separately.

The initial optimum start values are set at thirty-five minutes for heating and forty-five minutes for water. The values are progressively modified after the first day's operating, on a self-learning basis; an important exception is that records are not updated when an Override is operated, so the controller will be slower to learn requirements if Overrides are frequently used in the early days of a new installation.

On installation, the Controller should be set with the day of week and the current time, then left running with the factory set heating programmes. These programmes have been developed and tested in user trials and it has been found that some 85% of users are content to run their heating systems without making changes. Users are therefore advised to run with the factory set programmes, in order to gain initial experience, making only ad hoc Override adjustments to find the temperature settings that they find most comfortable; with one or two exceptions, that are described in the operating instructions, they are advised against changing the standard programmes during the first week or so.

The standard programmes vary the central heating and water temperatures, according to the time of day, thus ensuring that comfortable levels are maintained and waste is avoided by not running heating when it is not needed. A feature of the standard programmes is the overnight heating programme with a low temperature setting that is set to ensure that a satisfactory minimum level is maintained, whatever the weather; the cost of this heating is normally offset by a saving in the first or "wake up" programme of the day as it only operates in very cold weather. The overnight programme has been found to be especially beneficial for elderly people, those with small children, sufferers of Angina, Asthma, Bronchitis, etc.

The controller may be reset to the original factory installed configuration and heating programmes. This may be necessary if major changes are made to the heating installation or the controller is moved to another building. The facility to reset the whole controller with the factory installed configuration is different from and should not be confused with the heating programme reset that forms part of the Override facilities.

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Optimum Start (Time Heat Required) An optimum start facility that enables the user to set the time and temperature that heat is required for central heating, or for hot water, is quite different from the conventional setting of time clocks for on and off times. It offers significant advantages in terms of convenience and comfort, as well as enabling substantial energy savings over time clock systems which switch on and off the heating mechanism at a standard preset time, whatever the weather conditions happen to be. It ensures that heat is provided when required, yet avoids waste incurred by switching on too early on warmer days, by relieving the user of guesswork and allows him simply to set the system with details of the heating temperature needed and when the temperature specified is required.

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Furthermore, when a central heating or water heating programme is followed by another programme with a higher temperature, the currently running programme may be cancelled automatically to allow the later programme to start early to warm up to the higher temperature when conditions make this desirable. Thus, for example, an evening programme that runs to 6.30 p.m. at 19C, that is followed by a programme that requires a temperature of 21C, may be superseded by the later programme at 6 p.m., or whatever earlier time may be appropriate for the prevailing weather temperature conditions, in order to raise the temperature to 21C by 7 p.m.

The DCD designed system employs a method of progressive updating of heating history data based on actual performance, with approximately six thousand cells of stored information. The history is used to predict independent warm up times for both water and central heating, for each set heating programme, according to stored data for the nearest similar prevailing weather and heating conditions. Optimum start normally offers the greatest benefit when a house is warmed up first thing in the morning and the chart, reproduced above, shows the effect on three consecutive Winter days that were taken at random. It will be appreciated that a standard time clock system, or one based on a simple optimising algorithm, without regard to water heating requirements, could not match the performance of the DCD optimum start system in the three days illustrated.

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Smoothing of Central Heating

With a conventional domestic heating system, heating cycles involve heating radiators from a relatively low temperature and then switching the heating off when the room thermostat reaches a set temperature. The radiators effectively hold a reservoir of heat when the room thermostat reaches temperature and, after the heating is switched off, the room temperature continues to rise as this heat is dissipated by the radiators.

With the smoothing system, operational experience is recorded and used to adjust and smooth out heating cycles. This offers advantages in terms of greater comfort by avoiding fluctuations in temperature, and in terms of savings in energy, by smoothing or evening out peaks when rooms would otherwise be heated beyond the temperature that is needed for comfort. Furthermore, while boiler cycling is regulated to obtain fuel economies and to minimise maintenance costs, the controller does not restrict boiler output in order to obtain fuel economies at times when the full power of the boiler is needed to maintain maximum comfort.

An appreciation of the benefits of the DCD Smoothing System will be found in the summary of the report by the Building Research Establishment.