MEP

Question 1

What is mechanical system of a building?

Answer 1

Mechanical systems most commonly relate to heating ventilation and air conditioning systems, but they can also relate to transportation systems such as lifts and escalators, elements of infrastructure, industrial plant and machinery, and so on.

Question 2

How buildings losses heat?

Answer 2

• Fabric losses – heat transfers through the floor, walls, roof and windows of a building
• Ventilation losses – heat loss when old air is ventilated from building
• Infiltration losses – unintentional losses through gaps and cracks in building envelope

Question 3

What are the main heat sources in a building?

Answer 3

• Solid fuel – timber, coal, peat, biomass.
• Liquid – oil, liquid petroleum gas (LPG).
• Gas - natural gas, biogas.
• Electricity - grid, wind turbines, hydroelectricity, photovoltaics.
• Water – solar thermal, geothermal, ground source, water source.
• Air source.
• Heat recovery.
• Passive – solar gain, thermal mass.
• Internal heat loads - heat generated by people and equipment.

Question 4

What are the main heat generators?

Answer 4

• Boilers.
• Solid fuel burners.
• Combined heat and power (CHP) plant.
• Electrical heaters.
• Gas heaters.
• Heat pumps.

Question 5

How is heat distributed within a building?

Answer 5

Heat generators can be local to the demand for heat, or can be centralised and distributed, either within a single building or on a wider basis as part of a district heating network. Heat distribution can be by:

• Air blown through ducts, plenums or occupied spaces.
• Water pumped through pipework.
• Steam distributed through pipework.
• Passive air movement.
• Passive diffusion of heat through thermal mass.

Question 6

How heat can be delivered within a building?

Answer 6

• Fan coil units.
• Air handling units.
• Radiating panels.
• Embedded pipes in thermal mass.

Question 7

What are the heat transfer mechanisms?

Answer 7

• Radiation.
• Convection.
• Conduction.
• Phase change.
• Underfloor heating

Question 8

How heating can be controlled?

Answer 8

• Locally by manual or automated thermostats, switches or dampers.
• Centrally by manual or automated thermostats, switches or dampers.
• Building management systems.

Question 9

What is Combined heat and power (CHP) plant?

Answer 9

Combined heat and power (CHP), sometimes referred to as cogeneration, is a process in which the heat that is created as a by-product of power generation is captured and used rather than simply being wasted.

Question 10

What is Air Handling unit?

Answer 10

Air handling units (AHU, sometimes referred to as ‘air handlers’) form part of the heating, ventilating and air conditioning system (HVAC) that supplies, circulates and extracts air from buildings. Generally, they are connected to the ductwork that supplies air to and extracts air from the interior and can provide ventilation, heating, cooling, humidity control and filtration.

Question 11

What is Fan Coil units?

Answer 11

Fan coil units (FCU) consist of only a fan and a heating or cooling element, are located within the space they are serving, and are generally not connected to ductwork. They may either just recirculate internal air, in which case a separate ventilation system is required, or may introduce s proportion of ‘fresh’ air that is mixed with the recirculated air.

Question 12

What is Energy Centre?

Answer 12

Energy Centre is general term of the main heat generating plant and associated equipment. A modern energy centre typically contains a combined heat and power unit, back up boiler, thermal storage vessel, water treatment equipment and expansion vessels.

Heat is then distributed to the network through flow and return pipework.

Question 13

What is Heat Interface Units (HIU)?

Answer 13

Heat Interface Units (HIU) are typically used during the construction of large apartment complexes and social housing projects. Here rather than each property or dwelling being fitted with an individual boiler, a central boiler is used to provide heat and domestic hot water to all dwellings.

Question 14

What are the factors determining the choice of ventilation systems?

Answer 14

• predicted heat gains to the space
• occupant usage patterns
• External noise levels and air quality
• the need for removal contaminated air

Question 15

What are the main methods of ventilations?

Answer 15

• natural ventilations
• mechanical ventilation (extract only, supply only, supply and extract systems)

Question 16

How supply and extract ventilation system work?

Answer 16

A supply and extract system comprises a central handling unit (AHU) typically containing separate supply and extract funs, air filter and heating coil. A ductwork system is used to supply and extract air from around the building. the heating coil can provide the main source of heat for the building.

Question 17

What are the main method of managing ventilation in a building?

Answer 17

• Natural Ventilation,
• Mechanical ventilation
• Comfort cooling
• Air conditioning

Question 18

What HVAC stands for?

Answer 18

Heating, ventilation and air-conditioning system

Question 19

What are the types of air condition systems?

Answer 19

• centralised air systems
  
  • Constant volume (CV)
  • Variable air volume (VAV)
  • Displacement ventilation
• partially centralised air/water system
  
  • fan coil units
  • chilled beams
  • chilled ceilings
  • room based heat pump
• Local systems
  
  • Split systems
  • Variable refrigerant flow

Question 20

What is VAV?

Answer 20

• Variable Air Volume (VAV) in which the temperature of the supply air remains constant, but the volume varies (also known as variable volume, constant temperature VV-CT).
• In simple VAV systems, air handling units (AHU) supply air through ductwork to spaces within the building, and the temperature of the spaces is moderated by adjusting the supply flow.

Question 21

What are the chilled beams?

Answer 21

• Typically, chilled beams are distributed regularly across the ceiling of a space. They include chilled water pumped through copper cooling coils bonded to aluminium fins that cool air by convection.
• Very broadly, chilled beams can be passive or active.

Question 22

What are chilled ceilings?

Answer 22

• Radiant chilled ceilings typically incorporate a network of chilled water coils in ceiling panels with insulation above. In some systems, pipework may be incorporated into plasterboard, but this is less efficient as plaster is an insulator. The ceiling surface then cools the occupied space by both radiation and convection. This provides even temperatures throughout the space and avoids draughts.
• Very little space is required for chilled ceilings, which may be installed with a depth of just 100mm. In some systems, small bore cooling coils can be embedded in plaster ceiling finishes themselves.

Question 23

What are split systems?

Answer 23

Split systems are made up of two components: one or more indoor room cooling units and an outdoor refrigerator unit which dumps heat taken from the building.

the indoor and outdoor units are linked by pipes which transport refrigerant between the units.

Question 24

How can you control building services?

Answer 24

• Manual control
• Analogue controls
• Direct digital controllers (DDC_
• Building management system (BMS)
• Integrated System

Question 25

What does FCU/AHU/VAV stand for

Answer 25

• FCU- Fan Coil Unit
• AHU – Air Handling Unit
• VAV – Variable Air Volume System

Question 26

Why do we install generator in the building?

Answer 26

Generators are normally installed in building to act as a back up power supply should the primary power supply fail

Question 27

What is power generator?

Answer 27

The term ‘power generation’ describes the process of generating electrical power. Types of power generation include:

• Fossil fuel thermal energy such as coal or natural gas.
• Biogas energy.
• Geothermal energy.
• Hydroelectricity.
• Wind energy.
• Solar thermal energy.
• Tidal energy.
• Photovoltaics.
• Nuclear energy.
• Chemical energy generated from fuel cells, batteries, and so on.

Question 28

Name some On-Site power generator

Answer 28

• Photovoltaic – converts sunlight directly to DC electricity. The solar cells consist of a thin piece of semiconductor material (silicon).

• Combined Heat and Power (CHP) – know as a co-generator, is the generation of both heat and electrical power from the same source.
• Fuel cells – electrochemical device that can covert the chemical energy of a reaction into the low voltage DC.
• Standby Generator – to provide back up power supplies in the event the normal main power supply fails.
• Uninterrupted Power Suppliers (UPS) - two types: rotary and static; they have two key functions:

o to ensure the continuity of the power supply, irrespective of fluctuation or interruptions. this is essential service for critical services such as IT and communication system.

o to provide a clean and stable power supply free from power quality issues such as spikes, sags and harmonics.

Question 29

How is electricity supplied to a building?

Answer 29

1. Originates from power plant – which generate the energy from col, natural gas or nuclear. Typically, coat is burned to create a heat
2. The heat creates water to create a steam to drive a turbine which Is connected to generator. The turbine creates there phase electricity at 25kV altering current (AC).

The electricity voltage is then increased by step up transformer for transmission on national grid at 132kV, 275kV or 400kV

3. At points of use, High Voltage (HV) distribution is reduced via step down transfer to 33KV for heavy industry buildings, 11kV for light industry and large commercial and to 400V or 230V for small commercial and domestic building.
4. the voltage is then transfer to main distribution swich board containing Air Circuit Brakers and then sub-distribution board into final circuits.