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Specifying controls

Sarah Delany, NBS technical author, introduces a new approach to the specification of services controls.

The E&W Building Regulations Part L1 requires provision and commissioning of ‘energy efficient fixed building services with effective controls’, towards the conservation of fuel and power in buildings. It is therefore important that the controls system is designed and specified to ensure the requirement is met.

Specifying controls for engineering services is predominantly a matter of describing the performance of the controls rather than the equipment to be used to achieve the control. Controls organizations have different ways of achieving the end result which can all be valid, and it is important to produce a specification that can take advantage of this expertise. Whether you are specifying controls for local heating and hot water, or for a full building management system where security systems are linked with access systems and CCTV systems, it is the performance of the control system that is most important.

Within the NBS Engineering Services section structure is a subsection for describing system performance, which is ideal for this type of specification. However, producing a set of generic specification clauses for describing performance of controls is rather more of a challenge than for products such as boilers and generators.

Terminology within the controls industry has not kept pace with developments in technology over the last ten years, which have increased the scope of controls throughout the whole building. The ability to monitor and manage plant centrally and remotely has opened the way to complex interlinking of many systems throughout a building and the terms ‘building management systems’ (BMS) and ‘building energy management systems’ (BEMS) are not as clearly defined as they were.

The NBS Engineering Services section on controls (Y40) has been rewritten to take account of these factors and to make the preparation of a controls specification an easier process. The current section covers all controls, which is a very broad scope. It has been replaced by two sections: Y40 Mechanical engineering control and monitoring systems and Y41 Building monitoring and management systems.

Y40

The new section Y40 has been limited to the control and monitoring of all the mechanical engineering services, e.g. water supply, heating, cooling and air conditioning. Y40 is designed to be used to describe either a central control system or local control systems. A set of generic clauses describing system performance allows the selection of appropriate equipment performance clauses covering all types of equipment, from boilers and chillers to pumps and fans. The method of start and stop control and the interlinks between items of plant can also be described. The clauses are based on the information contained in the specification sections of BSRIA Application Guide 7/98 Library of system control strategies. This document includes schematics, descriptions of the control philosophy and the control strategy of many different items of plant for both air and water systems. At the end of each plant item is a BMS points list, a summary of plant operation and a flow chart.

An important part of controlling the use of fuel and energy is to monitor the operation of the plant to ensure it is operating efficiently. Section Y40 includes clauses for data logging information from equipment such as actuators and three port valves, and clauses for including requirements for plant monitoring equipment such as fans and pumps. This information can be used in managing and analysing plant operation.

Clauses with details for equipment such as control panels, actuators, motorized valves and sensors are included in the Products subsection.

Information on the commissioning of the controls system is included in NBS Engineering Services section Y50.

Y41

A new section, Y41, has been created for building monitoring and management systems, e.g. CCTV, access control, energy management and lighting control systems.

Section Y41 is a series of clauses for describing input signals, control modes and output actions for different systems. Many of the relationships between systems will be project specific and could include the function of turning on CCTV in an area where a security alarm has operated, or activating lighting and temperature control in an office when the person using that area enters the building through the access entry system. The system might also monitor energy consumption and plant operation so that maintenance can be managed. This information can be monitored and managed either locally or remotely by a facilities manager.

The work carried out to develop section Y40 and to introduce section Y41 provides a new approach to specifying controls and was done with the help of consultants and controls specialists. Feedback on the content and ease of use of the sections can be sent to info@theNBS.com.