Electrical & Mechanical Controls Ltd – EMC LTD 21 Years of experience counts. Phone 01603 625535


Why do we need a Building Management System?

All Buildings have some form of mechanical and electrical services in order to provide the

facilities necessary for maintaining a comfortable working environment. These services

have to be controlled by some means to ensure, for example, that there is adequate hot

water for sinks, that the hot water in the radiators is sufficient to keep an occupied space

warm, that heating with ventilation and possibly cooling is provided to ensure comfort

conditions wherever, irrespective of the number of occupants or individual preferences.

Basic controls take the form of manual switching, time clocks or temperature switches that

provide the on and off signals for enabling pumps, fans or valves etc.


The purpose of a Building Management System (BMS) is to automate and take control of

these operations in the most efficient way possible for the occupiers/business, within the

constraints of the installed plant.


What is a Building Management System and how does it work?

The BMS is a “stand alone” computer system that can calculate the pre-set requirements of

the building and control the connected plant to meet those needs. Its inputs, such as

temperature sensors and outputs, such as on/off signals are connected into outstations

around the building. Programmes within these outstations use this information to decide the

necessary level of applied control. The outstations are linked together and information can

be passed from one to another. In addition a modem is also connected to the system to

allow remote access.


The level of control via the BMS is dependent upon the information received from its sensors

and the way in which its programmes tell it to respond to that information. As well as offering

a precise degree of control to its environment, it can be made to alarm on conditions that

can’t meet specification or warn of individual items of plant failure.

Occupancy times for different areas are programmed into the Building Management System

such that the plant is brought on and off to meet the occupier requirements.

These times are often under optimum start control. This means that the heating plant is

enabled, at a varying predetermined time, to ensure that the heated space is at the set

desired temperature for the start of the day. The Building Management System therefore,

based on the outside air temperature the space temperature and the building structure,

determines the plant start time. The maintenance operative at a large site will have

some knowledge of the Building Management System, but will not have the benefit of the

detailed training for the commercially available systems.