Controls can have a significant impact on the energy value calculated by DEAP. Table 4.8 of the DEAP manual defines the control category based on the type of controls installed in the dwelling. There are various groups of controls to select from based on the heating system type in Table 4.8. More recently, controls are provided via mobile Apps, enabling remote control of heating temperatures and scheduling. Determine the applicable level of control from the Heating control list below for these Apps when identifying the appropriate DEAP entries.
This information is required on BER certificate. The check box in the DEAP software facilitates its inclusion on the BER certificate, without having any impact on the primary energy calculation in DEAP. For systems using underfloor heating, this answer is assumed to be yes. For radiator-based systems the answer is assumed to be no, however, where an applicable sign-off from the system installer confirming that the distribution system could operate at a lower or more efficient temperatures, then the answer can be yes.
The influence of the heating system controls is based on entries in the ‘Space heating: controls and responsiveness’ tab with reference to Table 4.8. The following are descriptions of the types of controls accounted for in this table.
A room thermostat senses the indoor air temperature and switches on or off the space heating. Unless otherwise specified in guidance, the user must be able to set a single target temperature.
A switch operated by a clock to control either space heating or hot water, but not both. The user chooses one or more on periods, usually in a daily or weekly cycle
Two switches operated by a clock to control both space heating and hot water. The user chooses one or more on periods, usually in a daily or weekly cycle. A mini programmer allows space heating and hot water to be on together, or hot water alone, but not heating alone. A standard programmer uses the same time settings for space heating and hot water. A full programmer allows the time settings for space heating and hot water to be fully independent.
A programmer may be specified in the following cases:
A combined time switch and room thermostat allowing user defined occupancy periods with different target temperatures for space heating, usually in a daily or weekly cycle.
A device or feature within a device, to delay the chosen starting time for space heating according to the temperature measured inside or outside the building. A regular room thermostat, as defined above, does not meet the criteria of a delayed start thermostat.
A radiator valve with an air temperature sensor used to control the heat output from the radiator by adjusting water flow. As shown in Table 4.8, a programmer and TRVs are generally required to affect the calculated energy use. At least 50% of the dwelling’s radiators should have TRVs to select this option in DEAP. Towel rails are not considered in the TRV count.
A cylinder thermostat measures the temperature of the hot water cylinder and can switch on and off the water heating. A single target temperature may be set by the user, or the thermostat may have a pre-set temperature.
A TRV on the cylinder or a thermostat on the cylinder pipework will not achieve this level of control and are not considered to act as a cylinder thermostat.
A cylinder thermostat is assumed present when the main water heating is from a group heating plate heat exchanger, an immersion heater, an integrated thermal store, a combi boiler or a CPSU. See Table 5.1 for further detail.
A flow switch detects when there is no water flow because the TRVs on all radiators are closed.
This is not a physical device but an arrangement of the system controls ensuring that the boiler does not fire when there is no demand for heat. Boiler interlock can be achieved by correct wiring interconnections between the room thermostat, cylinder thermostat, and motorised valve(s). It may also be achieved by a suitable boiler energy manager. Boiler interlock can be achieved for combi boilers by fitting a room thermostat.
In systems without an interlock, the oil or gas boiler cycles even though no water circulates through the main radiators or to the hot water cylinder. Boiler cycling reduces operating efficiency and Table 4.6 specifies that a gross seasonal efficiency reduction of 5% should be made for such oil or gas fuelled systems. Interlocked systems are systems where both the space and water heating are interlocked, and a reduction is not applied to system efficiency.
A cylinder thermostat normally shuts down the primary circuit pump when the hot water temperature set point is reached. The cylinder thermostat itself may not switch off the boiler; this is only done if the pump and boiler are interlocked and so the presence of a cylinder thermostat does not in itself signify the presence of an interlock for water heating. If there is no cylinder thermostat, however, there can be no interlock since the system does not know when the demand temperature is reached. A boiler system with no cylinder thermostat must therefore be considered as having no interlock.
A boiler system with no connected room thermostat (or a device equivalent in this context, such as a flow switch or boiler energy manager), even if there is a cylinder thermostat, is generally considered as having no interlock.
For solid fuel boilers and dry core electric boilers, the boiler interlock question is not relevant and the efficiency values in Table 4.4 allow for normal operation of these appliances. For such systems, there is no efficiency reduction for the absence of interlock.
Notes:
A fixed bypass is a piping arrangement that maintains minimum flow rate through the boiler by ensuring that one radiator stays open or by adding a short pipe with a valve between the flow and return pipe. A radiator without a TRV or hand valve is a common form of fixed bypass. Alternatively, a short pipe with a fixed position valve between the flow and return pipe can be used. An automatic bypass valve controls the water flow in response to the water pressure difference, typically by spring loading, so that the bypass operates only to the extent needed to maintain a minimum flow rate through the system.
The control type 'TRVs + programmer' is a non-interlocked system in the absence of other arrangements to provide the interlock function.
Typically, a device intended to improve boiler control using features such as weather compensation, load compensation, start control, night setback, frost protection, anti-cycling control and hot water override. It is equivalent to a hard-wired interlock. Other features such as weather compensation or load compensation are considered separately using the relevant DEAP guidance below.
In order to specify time and temperature zone control, it must be possible to program the heating times of at least two space heating zones independently in addition to one or more independent temperature controls (room thermostat) per zone. It is not necessary for these zones to correspond exactly with the zone division that defines the living area fraction, (see living area in section 2). Where the dwelling is more than 300 m2 floor area, then extra time/temperature zones are required as follows:
Table 4.2 – Number of zones required for time and temperature zone control
| Dwelling total floor area (m2) | Number of space heating zones required for Time and Temperature zone control |
|---|---|
| <300 | 2 |
| <300 and <400 | 3 |
| >=400 and <500 | 4 |
| Add 1 zone for each extra 100m2 | |
In the case of wet systems, separate plumbing circuits are required, either with their own programmer, or separate channels in the same programmer. By contrast, conventional TRVs provide only independent temperature control. If a TRV can be time controlled, and provides the same functionality as a room thermostat, it is considered as part of a fully zoned system subject to the guidance on control of the number of zones required as outlined in the table above.
Time and temperature zone control can be specified for electric systems, including under floor heating, by providing separate temperature and time controls for different rooms.
A device or feature which adjusts the temperature of the water circulating through the heating system according to the temperature measured outside the building. A regular room thermostat, as defined above, does not meet the criteria of a weather compensator.
A device or feature that adjusts the temperature of the water circulating through the heating system according to the temperature measured inside the building. A regular room thermostat, as defined above, does not meet the criteria of a load compensator.
There are three types of control that can be used with electric storage heaters: manual charge control; automatic charge control; and CELECT-type control. Automatic charge control uses internal thermostat(s) or an external temperature sensor to control the charging of the heaters. Availability of electricity to the heaters may be controlled by the electricity supplier on the basis of daily weather predictions. A CELECT-type controller has electronic sensors throughout the dwelling linked to a central control device monitoring the individual room sensors and optimising the charging of all the storage heaters individually (and may select direct acting heaters in preference to storage heaters).
Appliance thermostats on room heaters are typically identified as a thermostat mounted on the appliance, allowing its average heat output to be adjusted. The actual room temperature in the room may or may not be indicated on the appliance thermostat control.
In some cases, controls providing the functionality represented in different sections above are provided via mobile devices and enhanced systems incorporating software and user displays. These are entered in DEAP based on the applicable level of control identified above.