Air-Handling Unit (AHU): A device which forces air over pipes such that water in the pipes heats or cools the air. The air thus treated is blown into room spaces which require the warm or cold air. AHU’s may re-circulate a percentage of air drawn from a room or not. When cooling it is important that if colder air is available externally this is used for “free” rather than using chillers to cool warmer air.

Audit Report: A report which contrasts the performance of an existing control system in a building with Best Practice for that building (i.e. the ideal).

Back-end temperature: The return temperature of a boiler. This determines fairly accurately flue temperature, if too low condensates form, which if the fuel is sulphur rich are acidic and may damage plant. Generally when a boiler is enabled it should remain enabled until return temperature reaches 60 Celsius to prevent problems.

Best Practice: Generically a guideline from the UK government Energy Efficiency Best Practice programme (EEBPp) suggesting how a building should be controlled to be efficient.

As all buildings differ a total prescriptive recommendation is not possible to cover all possibilities. Therefore we define Best Practice as the control strategy which will meet building service requirements at minimum cost and environmental impact.

Boiler: A device used to heat water. It may be low or high pressure or a steam boiler. Water flows through tubes which surround a combustion zone where fuel is burnt in air. The fuel-air mix may be at atmospheric pressure or higher (blown gas).

Boiler/Chiller Sequencing: The control of activates of multiple burners/compressors to match the heat/chill load, so that unnecessary energy is not consumed.

BEMS (Building Energy Management System): An integrated system which reports on plant use in a building and allows a user to specify requirements for building users e.g. target temperatures and occupancy.

Burner: The device on the boiler which produces the flame – responsible for mixing fuel and air in correct proportions.

Burner Controller: The device which maintains control procedures over the burner to dictate when the burner burns. It ensure that safety procedures are in place and allows a management system to control whether the boiler is enabled. If a boiler is enabled it will produce heat if and only if safe to do so.

CHP (Combined Heat and Power or Co-generation): Any generation of electrical or motive power where heat that is generated as nominal waste in the process is utilised elsewhere. This heat is often called “free heat”. It is perhaps better thought of as by-product heat.

Compensation: Relation of a target temperature to another temperature. E.g. direct boiler compensation is where boilers produce lower temperatures on hotter days.

Compensation with automatic set backWhere compensation is employed it is possible for the target temperature to be met or exceeded in a space, automatic setback adjusts the compensation to match the requirements.

Compensation with automatic set back: Where compensation is employed it is possible for the target temperature to be met or exceeded in a space, automatic setback adjusts the compensation to match the requirements.

Delta: A difference between two temperatures (often flow and return) given a constant flow rate this is proportional to the net heat transfer across the sensor points.

DHW: Domestic hot water.

Direct Fired Water Heaters: High efficiency water heaters where water heated is for occupant use rather than as a heat transfer medium.

Exercising: Occasional deployment of plant to no purpose other than to maintain it (e.g. exercising valves can prevent them from sticking or locking through corrosion or scale build up.)

Fabric Protection: Operation of plant outside normal hours under cold conditions to prevent pipes freezing or condensation damage.

Header: The pipes immediately prior to and after a set of boilers in the primary circuit.

Implementation: The process of upgrading controls from existing methods to Best Practice, this may require new hardware, modification of software or simply fine tuning of the existing system.

Isolation valve (also butterfly): A valve which allows or prevents flow through a pipe.

Optimum start: The automated assessment of when plant needs to be enabled to achieve a target objective by a certain time. The BRESTART algorithm is recommended.

Pre and Post Purging: In a boiler which relies on compressed fuel-air mix prior to ignition and after extinguishing air is blown through the boiler with no fuel, this ensures that no unsafe ignition can take place.

Rotation sequencing: Changing duty patterns of plant to achieve similar objectives while ensuring approximately equal use of plant.

Sequential Start: Where on start separate zones are enabled at staggered times to prevent cold water slugs causing contraction stresses to plant.

Specification:  A document which describes changes to control facilities required to bring an existing control system in line with Best Practice.

Three-port valve (Bypass): Controls the proportion of flow from one pipe to which enters either of two other pipes.

Three-port valve (Mixing): Controls the proportional mixture of two separate flows to a valve to enter another pipe.

Twin Pump set: Two pumps which together share the role of creating flow in a pipe either both are off or one or the other is on. If an active pump fails then the twin takes over.

Zone:An area of a building with independently controllable building service provision. For efficiency zones should be separate where occupancy, uncontrollable gains or losses of heat/chill or target temperatures can be predicted to differ (e.g. north and south facing spaces).