Mechanical, electrical and plumbing (MEP) refers to the installation of services which provide a comfortable space for the building occupants. In residential and commercial buildings, these elements are often designed by a specialized MEP engineering firms. The part of Mechanical in the overall MEP system is almost 70% of the total work. MEP's design is important for planning, decision-making, accurate documentation, performance- and cost-estimation, construction, and operating/maintaining the resulting facilities.
MEP specifically encompasses the in-depth design and selection of these systems, as opposed to a tradesperson simply installing equipment. In countries of Asia such as Pakistan, China and Saudi Arabia the use of MEP is increasing in building construction projects due to extreme climates in summer and winter. For example, a plumber may select and install a commercial hot water system based on common practice and regulatory codes. A team of MEP engineers will research the best design according to the principles of engineering, and supply installers with the specifications they develop. As a result, engineers working in the MEP field must understand a broad range of disciplines, including dynamics, mechanics, fluids, thermodynamics, heat transfer, chemistry, electricity, and computers.
Design and documentation
As with other aspect of buildings, MEP drafting, design and documentation were traditionally done manually. Computer-aided design has some advantages over this, and often incorporates 3D modeling which is otherwise impractical. Building information modeling provides holistic design and parametric change management of the MEP design.
Maintaining documentation of MEP services may also require the use of a geographical information system or asset management system.
Components of MEP
Mechanical
The mechanical component of MEP is an important superset of HVAC services. Thus, it incorporates the control of environmental factors (psychrometrics), either for human comfort or for the operation of machines. Heating, cooling, ventilation and exhaustion are all key areas to consider in the mechanical planning of a building. In special cases, water cooling/heating, humidity control or air filtration may also be incorporated. For example, Google's data centres make extensive use of heat exchangers to cool their servers. This system creates an additional overhead of 12% of initial energy consumption. This is a vast improvement from traditional active cooling units which have an overhead of 30-70%. However, this novel and complicated method requires careful and expensive planning from mechanical engineers, who must work closely with the engineers designing the electrical and plumbing systems for a building.
A major concern for people designing HVAC systems is the efficiency, i.e., the consumption of electricity and water. Efficiency is optimised by changing the design of the system on both large and small scales. Heat pumps and evaporative cooling are efficient alternatives to traditional systems, however they may be more expensive or harder to implement. The job of an MEP engineer is to compare these requirements and choose the most suitable design for the task.
Electricians and plumbers usually have little to do with each other, other than keeping services out of each other's way. The introduction of mechanical systems requires the integration of the two so that plumbing may be controlled by electrics and electrics may be serviced by plumbing. Thus, the mechanical component of MEP unites the three fields.
Electrical
Alternating current
Virtually all modern buildings integrate some form of AC mains electricity for powering domestic and everyday appliances. Such systems typically run between 100 and 500 volts, however their classifications and specifications vary greatly by geographical area (see Mains electricity by country). Mains power is typically distributed through insulated copper wire concealed in the building's subfloor, wall cavities and ceiling cavity. These cables are terminated into sockets mounted to walls, floors or ceilings. Similar techniques are used for lights ("luminaires"), however the two services are usually separated into different circuits with different protection devices at the distribution board. Whilst the wiring for lighting is exclusively managed by electricians, the selection of luminaires or light fittings may be left to building owners or interior designers in some cases.
