Mechanical Contracting

An air conditioner is a system or a mechanical refrigeration machine that treats air in a defined, usually enclosed area via a refrigeration cycle in which warm air is removed and replaced with cooler air. A heat pump air conditioner is machine that can reverse its refrigeration cycle and instead of cooling the air to heat it up. In construction, a complete system of heating, ventilation, and air conditioning is referred to as HVAC.

Ventilation is the mechanical system in a building that brings in "fresh" outdoor air and removes the "contaminated" indoor air and to maintain indoor air quality for the humans.

In a workplace, ventilation is used to control exposure to airborne contaminants. Ventilation  is  needed to provide oxygen for metabolism and to dilute metabolic pollutants (carbon dioxide and odour) and pollutant from the structures and furniture. When, there are combustion appliances such as gas heaters inside indoor spaces with peoples, the spaces should be ventilated to provide oxygen to combustion appliances.

Ventilation  improves  indoor  air quality (IAQ) through mechanical means, such as through outdoor air intakes associated with the Heating, ventilation and air conditioning (HVAC) system and filtration.

Nowadays, the ventilation exhaust systems are combined with fresh air supply systems into a Heat/Energy Recovery system (ERU) so part of the cooling or heating energy contained in the exhausted air to be recovered and to be used in the pre-treatment of the fresh air supplied to the building.

The most widely used refrigeration method is mechanical compression  because of the well developed technology and availability of components.  Other type of refrigeration are: 
  • Absorption   Refrigeration 
  • Evaporative   Cooling 
  • Thermoelectric   Refrigeration 
  Mechanical Air conditioning systems are using refrigeration cycles but the term refrigeration is widely used in commercial application s  where rooms or warehouses are cooled below 16  0 C  ( coolers)  or   below 0 0 C (freezers). The refrigerated rooms are used to store commodities and products that will be corrupted and spoiled in ambient temperatures. 

A space heating system is a system that uses primary energy from hydrocarbon fuels or electricity or energy renewable sources such as wood pellets or from solar or a geothermal system to heat a room, a house, block of apartment houses, offices or hotels etc.

Space heaters are powered by electricity or a burnable fuel, such as natural gas, propane, fuel oil, or wood pellets. In the Northern Europe, the air conditioning systems for dwellings are solo heating ones as the cooling is not required.

However, in Southern Europe, the air conditioning systems must do both heating and cooling or to use one system for space cooling and another for space heating. In the past, heating of duelling was affected with radiators. Heating water produced by a boiler/ gas or gasoil burner system is circulated through the radiators which are heating the space by radiator and air convection.

The most popular heating system is a radiant floor system and it can be affected with electrical resistance wires or with hydronic piped floors. The most environmental friendly is the one that utilizes a heat pump heater which produces heating water by pumping the energy from the surrounding air. The technology of heat pump has developed so much that heat pump can pump energy even at ambient temperatures of -15 0C with a good efficiency. The heated floor radiates the heat to the space without any movement of the air.

In buildings, domestic hot water is required for sanitation in showers, baths, sinks and in kitchens for food preparation. Production of Hot water is an energy intensive process and different systems are employed depending on the application and budget.

Electric Resistors: A widely used method is the used of electric resistors. Industrial products built for the specific purpose are widely available in the market known as instant heaters, cylinder heaters etc. The used of electric heaters is usually limited to the production of hot water in isolated taps installed usually under counter tops in offices or small shops.

Direct or indirect fired Gas or Gasoil Cylinder heaters: Hydrocarbon fuels are burned in a boiler and hot water can be produced. The method is widely used in domestic and commercial applications especially where there is supply of natural gas and where due to the inclined weather ( very low ambient temperatures below -5 0C are present) and the use of renewables sporces such as solar or heat pumps is not effective.

High temperature Heat Pumps ( 60-65 0C): Nowdays, due to the evolution of the HP technologies and due to the EC’s compulsory directives and regulations, the heat pumps are widely used to prepare domestic hot water since are considered renewable sources and enviromental friendly with smaller energy foot print ( lower CO2 emissions). The ranges of available HP is very wide so the Hps are used both in residential, commercial and industrial applications. It is worth mentioning that due to the increasing cost of electricity or the cost of hydrocarbon fuels, heat recovery systems have become popular. For instance, a water chiller can be supplied with a desuperheater heat exchanger which gives the user the possibility to utilize the otherwise rejected to the environment heat to warm up water. In the market,there are heat pumps that can recover 100%the condensing heat of the refrigeration cycle through a water circuit. These heat pumps are called multipurpose or 4 pipe chillers etc. The multipurpose heat pump which can produce simultaneously and independently cooling or heating watetr are becoming popular in the hotel industry where the demand for domestic hot water is a prime expense.

Solar Systems: The used of solar systems for the production of hot water has become a must especially in the EC countries. In Cyprus, there is long tradition for solar systems since they have being widely used since the 70’s ; Once, Cyprus was a leader & pionner in the production and use of thermosiphon type solar heaters. Nowdays, the use of solar heater in the residential sector has been a standard choice dictated by the need to reduce CO2 emissions whereas in the hotel industry is obligatory as a term of the built permit.

Modern buildings cannot be inhabited or use without running cold and hot water services. The water is used in toilets, basins, sinks, showers, baths , dish washers and in clothes’ washing machines. In any catering or food processing water is needed in food preparation but for cleaning and sanitizing.

Usually, the fresh water from city mains is stored in plastic in tanks and then is pumped by a booster pump to the sanitary fittings.

The pipe distribution networks are made of a diverse type of materials. In the past copper pipe materials were dominating the sector but nowadays because of the development in the technology of plastics and the fact that plastics are more economical, plastic pipe materials are mostly used such as:

  • PPR Polypropylene Random Copolymer plastic
  • PEX (crossed linked polyethylene)
  • HDPE/MDPE (high or medium density polyethylene

The dirty soiled water from the toilets, wash basins, sinks, showers and other points of use inside the building are drained out to the sewer through a network of pipes either by gravity or with the aid of pumps.

In the past, the material used to build soiled water networks was galvanized iron or cast iron when reduced noise properties were sought. Nowadays, plastics pipes are mostly used either plain or in composite form such as: UPVC, Polypropylene (PP), polypropylene mineral composites (PP-MD).

The composite plastic pipes are pipes that have been designed to reduce the noise generated during the flow of liquids and emitted to the surrounding areas. Noise is important in certain application and nearly silent pipes are available in the market.

A swimming pool, swimming bath, wading pool, paddling pool, or simply pool is a structure designed to hold water to enable swimming or other leisure activities. In simple form, the mechanical system of a swimming pool consists of a circulating pump which draws water from main drains and skimmer overflow fittings/perimeter overflow channel, pasts it through a sand filter, through a chlorinator or other water treatment device and delivers it to the inlet nozzles inside the pool.

The Water in a swimming pool must be kept in circulation for many hours so the dirt and debris is removed and the bacteria and other pathogen microorganisms are destroyed when in contact to the chemical agent such a free chorine. A swimming pool owner must maintain the chlorine level of swimming pool water, the pool pH, pool Alkalinity, chlorine stabilizer (Cyanuric Acid), and pool Calcium Hardness levels so that to keep pool water clean and safe for swimmers.

Irrigation is the application of controlled amounts of water to plants at needed intervals. Irrigation helps to grow agricultural crops, maintain landscapes, and revegetate disturbed soils in dry areas and during periods of less than average rainfall.

The four main methods of irrigation are:

Surface: Water is distributed over and across land by gravity, no mechanical pump involved. Sprinkler: Sprinkler Irrigation is a method of applying irrigation water which is like rainfall. Water is distributed through a system of pipes usually by pumping. It is then sprayed into the air and irrigated entire soil surface through spray heads so that it breaks up into small water drops which fall to the ground.  Sprinkler irrigation is suited for most row, field and tree crops and water can be sprayed over or under the crop canopy. However, large sprinklers are not recommended for irrigation of delicate crops such as lettuce because the large water drops produced by the sprinklers may damage the crops.

Drip/trickle: Drip irrigation is one of the most efficient types of irrigation systems. The efficiency of applied and lost water as well as meeting the crop water need ranges from 80 to 90%. Subsurface: Subsurface irrigation, also designated as sub irrigation, involve irrigation to crops by applying water from beneath the soil surface. Subsurface drip irrigation is a low-pressure, high efficiency  irrigation  system that uses buried drip  tubes or  drip  tape to meet crop water needs.... Water is applied directly to the root zone of the crop and not to the soil surface where most weed seeds germinate after cultivation.

The most common  active type fire extinguishing system is the wet sprinkler system. In simple words, a net work of fire piping with sprinkler nozzles attached on it is kept under water pressure by a sprinkler booster system.  The other type of the fire sprinkler systems is:   
  • Dry pipe systems 
  • Deluge systems 
  • Pre-action systems 
  • Foam water sprinkler systems 
  • Water spray systems 
  • Water mist systems. 
Fire sprinklers  are activated   by  high heat  of the air above a fire . When a blaze ignites, the air directly above it heats  up  rapidly .  When the air  temperature reached the activation temperature of glass bulb of the sprinkler head, the glycerin -based liquid inside the bulb expands and the glass bulb brakes opening  the nozzle to allow water to flow. The water hits the reflector and  a   umbrella of water  is formed  to cover a given  area.  According to the space protected, the sprinklers can come  with different activation temperatures as well with   different type of deflector.  The activation temperature is  differentiated by  the color of the bub.  Each deflector during activation produces different type of water umbrella; hence we have Pendent, Upright, side discharge etc. The sprinklers can  be visible or concealed type.     Also, sprinklers according to the requirements of the engineering study can be of standard response of quick response. The difference between them is to the time required for the glass bulb to brake once the air temperature reached the activation temperature. The bulb of the standard response type has 5mm diameter whereas that of quick is only 3mm.   
dry fire riser   is a network of pipes with a double inlet at ground floor and landing outlet valves at any other floor. It is placed vertically usually in the staircases and it allows the fire brigade to connect its pumping equipment from the outside of the building, to pump  a  large amount of water to the landing valves.  Thus; t he firemen can connect the ir  portable hose with nozzle equipment at any floor  with fire outbreak  to manually extinguish the fire.  Usually, t he fire riser s are  required for all type of low  height residential  or office buildings.     The  wet fire riser   is   like  the dry riser but is permanently connected through a pumping set within the building to a large reservoir/tank of water. The wet riser is intended for tall  buildings, taller than 7 floors where  the fire brigade equipment cannot cope with the pressure required.  Because of the h eight , to balance the available pressure at each  level pressure  reducers are required  to be installed  before each landing valve . 
Fire hose reel systems  consist of pumps, pipes, water supply and  hose reels  located strategically in a building, ensuring proper coverage of water to combat a  fire . The  system  is manually operated and activated by opening a valve enabling the water to flow into the  hose  that is typically 30 meters away.  This system complements the dry risers and it is intended for low level buildings  that are usually extended horizontally so the firemen can fight fires at any position within the building. 
Automatic fire suppression systems control and extinguish fires without human intervention. Examples of automatic systems include  Mist  sprinkler system, gaseous fire suppression, and condensed aerosol fire suppression .    This  system  uses inert  gases —such as nitrogen, argon, and carbon dioxide—to reduce the oxygen level around the  fire  and suppress it in the process. The concentration of  gases used  in  INERGEN   systems  is safe to use around people.   Fire suppression systems are  used to extinguish or prevent the spread of  fire  in a building.  Suppression systems  use a combination of dry chemicals and/or wet agents to suppress equipment  fires .  The main  differences between  a  fire sprinkler and fire suppression  systems are how they extinguish  fires  and when each system would be ideal to use.  Fire  sprinklers use water to extinguish and control  fires , while  fire suppression  systems can use  several   different  agents.  The Five Main Types of Fire Suppression 
  • FM200  or INERGEN  Gas systems  
  • Kitchen Fire Suppression – Chemical Foam ( Amerex , Ansul  etc ) This system is specifically designed for commercial kitchens. ...  
  • Water mist System. ... 
  • Foam Deluge System. ... 
  • Pneumatic Heat Detection Tube. 

Fire compartmentation  is an important element of 'passive  fire  protection' and is achieved by dividing the premises into ' fire  compartments' thought t he use of  fire  doors, floors and walls of  fire -resisting construction, cavity barriers within roof voids and  fire  stopping to services that penetrate through these compartments.

  • Fire protection to the structural frame of the building
  • Fire-resisting doors and fire door furniture
  • Fire shutters
  • Compartment walls and floors
  • Fire-resisting walls and partitions
  • Suspended ceilings
  • Fire-resisting glazing
  • Fire doors and hardware
  • Industrial fire shutters and curtains
  • Fire fighting shafts and stairwells
  • Fire-resisting dampers (mechanical or intumescent) used in horizontal or vertical air distribution ducts
  • Fire-resisting ductwork
  • Fire-resisting service ducts and shafts
  • Penetration seals for pipes, cables and other services
  • Cavity barriers
  • Fire-resisting air transfer grilles (mechanical or intumescent)
  • The building envelope, e.g. fire-resisting external walls, curtain walls etc.
  • Reaction to fire coatings
  • Hydrocarbon structural fire protection systems /li>

A  smoke  control  system  controls the flow of  smoke  in a  building  in the event of a fire. It keeps  smoke  from spreading throughout the  building  and gives the  building's  occupants a clear  evacuation  route, as well as preventing further damage to the  building's  interior .

Smoke control systems are one of the most complicated and often misunderstood systems within a facility, and rightfully so. It’s important to point out that a true Smoke Control System vs a post fire Smoke Management System are two entirely different animals. To use an analogy from the animal kingdom which illustrates the differences between these two systems let ’ s consider the use of water by a fish (Smoke Control System) and a camel (Smoke Management System). Both the fish and the camel need water to survive, however a fish uses the water as a medium in which to live while the camel uses its water as fuel to travel great distances.  Similarly, a Smoke Control System manages the medium of smoke in order to increase egress times so that occupants can escape safely. Conversely, Smoke Management Systems are used during post fire events to remove smoke from a facility and/or restrict smoke from entering specific areas of a facility during general evacuation.

A  Smoke Control System  can be defined as an engineered electro-mechanical system that uses mechanical fans and dampers in cooperation with electronic monitoring and controls to produce pressure differences across smoke barriers which inhibit or facilitate smoke movement. A smoke-control system is used to achieve one or more of the following design objectives:

  • -Inhibit smoke from entering stairwells, means of egress, areas of refuge, elevator shafts, or similar areas
  • -Maintain a tenable environment in areas of refuge and means of egress during the minimum required evacuation time
  • -Inhibit the migration of smoke from the smoke zone
  • -Provide conditions outside the fire zone that enable emergency response personnel to conduct search-and-rescue operations and to locate and control the fire
  • -Contribute to the protection of life and to the reduction of property loss

A smoke management system is applied to one or more of the following intended uses

  • -Roof hatch ventilation for smoke removal in high atrium spaces
  • -Maintain a tenable environment in areas of refuge and means of egress during the minimum required evacuation time
  • -Smoke exhaust fans in parking garages
  • -Pressurization fans in stairwells and/or elevator shafts

Understanding the Smoke Control design and installation process can be difficult with challenges at each phase of the project.  These systems are generally code mandated based on occupancy type, architectural construction methods, occupancy loads and a variety of other factors. With no single entity or trade being solely responsible for the entire solution, the interdependency across all professional engineering and installation trades is critical for a successful project.

What are the recommended indoor temperature and humidity levels for homes?

The ASHRAE Standard 55-2017, Thermal Environmental Conditions for Human Occupancy, notes that for thermal comfort purposes, temperature could range from between approximately 19 and 28 °C. A more specific range can be determined from the standard but depends on relative humidity, season, clothing worn, activity levels, and other factors. The standard notes that HVAC systems must be able to maintain a humidity ratio of at or below 0.012. This corresponds to an upper relative humidity level as high as more than 80% at low dry bulb temperatures but may be lower dependent upon factors such as temperature and the other factors listed above. The standard does not specify a lower humidity limit but notes that non-thermal comfort factors such as skin drying, irritation of mucus membranes, dry eyes, and static electricity may place limits on acceptability of very low humidity environments. ASHRAE Standard 62.1-2016 recommends that relative humidity in occupied spaces be controlled to less than 65% to reduce the likelihood of conditions that can lead to microbial growth.

The HVAC mechanical contracting comfort field is dealing with the installation mechanical systems that can provide an artificial indoor climate environment able to meet the comfort need s of the human occupants . Similarly, in industry there is need to maintain an artificial environment to facilitate an industrial process like food preparation or to facilitate working conditions for industrial equipment like a data center. Hence; Heating or Air conditioning systems can raise or lower the temperature /humidity in a controlled manner. The systems are provided with temperature /humidity control system s so the users, depending on the season, clothing worn, activity lever etc , to be able to select their individual comfort conditions that the system would provide. Be able to provide comfort conditions , it is very important because the productivity of the individuals is highly dependent on the comfort levels.

The simplest type of control system is an on/off thermostat or a hydrostat which switch off and on the source of heating / cooling or a humidifier of a dehumidifier acc o rding to the temperature set by the user. Today, the thermostats are fully electronic, smart with connectivity to internet. Depending on how precisely one wants to control the fluctuation on temperature/humidity the control systems can become quite complicate and quite expensive.

In an electric power system, switchgear is composed of electrical disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults downstream

Electricity is used to produce lighting and to power motors and appliances. To power and to switch on /off electricals loads of high voltage either single phase 230V or 3-phase 400V safely, we need   switch gears  such as  the contactors/relays and switches which are housed in distribution boards or panels.

The electrical panel with motorized switchgear usually has a primary high voltage electrical circuit of voltage 230V/400VC and an auxiliary low voltage 24 V control circuit .The low voltage control circuit  helps as to extend safely  the  controls outside the cubicles of the Electrical panels inside the building  so as to switch on/off loads and to monitor their operation  without  needing to provide isolation and without putting in danger the operators in case of electrical leakage.

A control circuit  is any  circuit  that has as its load, the operating coil of a magnetic motor starter, a magnetic contactor, a relay, a pilot light, or any other  control  device that exercises  control  of another  circuit . In other words, a  control circuit  exercises  control  over one or more other  circuits .

Building Energy Management Systems  (BEMS) are integrated, computerized   systems  for monitoring and controlling energy-related  building services   plant  and  equipment  such as  heating, ventilation and air conditioning  ( HVAC )  systems ,  lighting ,  power   systems  and so on. The phrase  Building Energy Management Systems  is sometimes used interchangeably with  Building Management Systems  (BMS), however, strictly speaking,  Building Management Systems  can be used to monitor and control a wide range of  building systems , including  fire ,  smoke detection  and  alarms , motion detectors,  CCTV ,  security  and  access control ,  lifts  and so on.  Building Energy M anagement Systems  relate specifically to energy-related  systems . Small  buildings  may have independent controls for  energy   systems , but for larger or more complex  buildings ,  sites  with a number of  buildings , or  organizations  with  buildings  on a number of  sites , the integration of  systems   operation  through a single  Building Energy Management System  offers greater control and can achieve significant savings

Increasingly, simple BEMS are being developed that are suitable for even the smallest  buildings . BEMS provide  real-time  remote monitoring and integrated control of a wide range of connected  systems , allowing modes of  operation ,  energy use ,  environmental   conditions  and so on to be monitored and allowing hours of  operation ,  set points  and so on to be adjusted to optimise   performance  and  comfort . BEMS can also trigger  alarms , in some cases predicting problems and informing  maintenance   programmes . They allow  records  to be kept of historical  performance , enable  benchmarking  of  performance  against other  buildings  or  sites  and may help automate  report  writing. Claims  for the  scale  of savings that can be achieved by BEMS range from 10% to 25%. 

Operated  properly, they should allow  energy use  to be optimised without compromising  comfort  or  performance . However this requires a thorough understanding of how  buildings  are supposed to perform, and how different  systems  within them interact. To  function  correctly they must be properly designed,  installed  and commissioned and must have a  user   interface  that is easy to  operate . They should then be continually assessed and fine-tuned as  performance  is better understood over a number of seasons and modes of  operation , and changes are made to  buildings  or  operations .  Maintenance  is also necessary to ensure  systems  continue to  operate  correctly, for example, replacing sensors and  batteries , checking connections, checking the  operation  of dampers and  valves , upgrading  software  and so on. BEMS can be wired or wireless  systems . To determine whether a wired or wireless  system  is the most appropriate,  buildings  should be audited to test how well signals can be received and how likely disturbances are.

Choosing the correct BEMS  system  then depends on the size and usage of the  building , the  scale  of the  project  and the  budget . As a general rule, larger, more extensive  projects  tend to be best suited to wireless solutions. BEMS may have remote outstations that can be interrogated locally, or may be  accessible  from mobile devices. However, major  buildings  may be vulnerable to cyber attack , especially when they are associated with prominent  organisations . This can be a particular issue where  functions   operate  in the 'cloud', such as cloud-based  analytics , and the ability to  access  and manage multiple  buildings  remotely. The ability to  access  live  analytics , or receive  alarm  notifications from hand-held devices has great potential benefits, but may also bring additional  risks .