R2 System - A Boon For HVAC Industry

 Energy Efficiency is a very important factor these days, which drives our aim to become a Global, Leading Green Company.

  The Mitsubishi Electric Group established Environmental Vision 2021 to contribute to the development of a sustainable society, and is advancing initiatives to achieve a low-carbon, recycling-based society. While this vision represents the company, we aim to become by the 100th anniversary of our founding in 2021, our ultimate goal is to make lasting social contributions as a leading green company.

  To this end, we are working to strengthen our corporate constitution and to contribute to society. Strengthening our corporate constitution refers to disciplining ourselves to use less energy and fewer resources in our manufacturing, and increasing production efficiency to the highest level possible. Specifically, this means reducing waste generated during production and thoroughly implementing the "3Rs" of resources: reduce, reuse and recycle.

  Mitsubishi Electric products are made with a vision of “Eco Changes for a greener tomorrow,” which is our commitment to the society to develop energy efficient products.

A winning combination for HVAC

  With the advance of technology, Variable Refrigerant Flow (VRF) type air conditioners are now capable of transferring the heat energy from inside the room to hot water. VRF is an air-condition system configuration where there is one outdoor condensing unit and multiple indoor units. The arrangement provides an individualised comfort control, and simultaneous heating and cooling in different zones.

  Most leading brands in air conditioners like Mitsubishi Electric have introduced two-pipe or three-pipe VRF systems that provide simultaneous heating and cooling.

Two-pipe system with simultaneous heating and cooling operations

  Heat recovery type VRF systems are normally available in water cooled and air cooled systems. In water cooled type systems, a double heat recovery is possible. The refrigerant from the condenser and indoor units (which are a mix of vapour and liquid) is passed through a set of valves, which separates the gas and liquid and diverts the flow of refrigerant to required indoor units, depending upon the heating or cooling requirement. These types of VRF units can have special type of indoor units known as air to water type. They have refrigerant and water passing through a plate type heat exchanger and depending upon the temperature settings on the water side part of indoor, the valve assembly diverts the refrigerant for heating or cooling of water.

Cooling main with hot water generation...

50% Cooling with 50% hot water Generation.
( Most energy efficient operation)...

Schematic diagram of Booster unit...

  What helps is that a maximum amount of energy efficiency is obtained after water is heated when the other indoor units are in cooling operation. It also means that a simultaneous generation of hot water and heating by indoor units is possible during the operation. While air cooled outdoor units will expel unutilised energy into the atmosphere, water cooled units can be used for double heat recovery – expelling the energy to water which can then be used for pre-heating the water for other applications.

  A schematic diagram of typical heat recovery system with hot water generation has been mentioned above.

Features of the system

  The system provides two types of air to water indoor units. The first one is the Auxiliary unit which recovers available heat from air conditioning operation with a maximum water temperature up to 40° Celsius. The second one which is the Booster unit contains an additional inverter driven compressor which can generate water up to 70°Celsius.

  The number of air to water indoor units have to be selected depending upon the hot water requirement. The capacity of the auxiliary unit is available with 12kW and 25 kW heating capacity with a maximum temperature output up to 40°Celsius.The capacity of Booster unit is 12 kW with a maximum outlet temperature up to 70°Celsius. The maximum connectivity of air to water type indoor units are 50 to 150 per cent when connected with standard indoor units. Outdoor capacity is available from 08 HP to 36 HP capacity in air cooled type.

  The selection of the capacity of air to water indoor units is calculated on the basis of a formula like this:

  Capacity of Air to water indoor (in kW) = {(T2-T1) x 1 Kcal/Deg hour x Water qty in Liters} / 860.

  (Adding a safety factory of 15 per cent to the derived kW from above calculation is important) T2 – water outlet temp, T1- water inlet temperature.

  The maximum water flow rate for the Air to Water series is 0.6 m3 / hr to 2.15 m3 / hr, the operating pressure is 1 Mpa and the output temperature for water is 10° to 40°Celsius (70°Celsius for Booster type units).

A technological marvel

  While understanding the features is easier, some questions still remain unanswered. An often-asked question is: can we get hot water even if the air conditioner is not operating? The answer to this is an emphatic yes! Hot water is generated irrespective of the operation of the other indoor units. However, the best efficiency is when other indoor units with a capacity equal to the air to water type indoor units are operating in cooling mode. (50% cooling, 50% for heating water).

  Since the air to water type indoor units are multi-pass storage type, increase in temperature at a single pass is generally less than 5°Celsius. A storage tank with a closed loop system and multiple passage of water to increase the temperature is needed.

  Many people wonder whether such a system can be used along with a solar type-water heater. Air to water type indoor units can be used to increase the feed water temperature to solar water heaters and can also be used to maintain the temperature of the water at a desired level during the night or in low sunlight periods. This applies mainly to the hotel industry where the requirement of hot water is high during early morning hours.

The recommended water quality standard is  JRA-GL02E  or equivalent...

System for India?

  One may also wonder if this type of system is suitable for the water quality that is available in India. While using the system in India, it is mandatory to use a closed loop system with the storage tank and air to water type indoor units. This helps in maintaining the efficiency of the system, and also prevents scaling inside the air to water type indoor units. Periodically PHE (Plate Type Heat Exchanger) inside the storage tank can be replaced. It is advisable to use de-mineralised water between the PHEs.

Source: http://coolingindia.in/blog/post/id/10009/r2-system-a-boon-for-hvac-industry

Energy Conservation in Clean Room

Clean rooms have controlled environment, where low level of pollutants such as dust, airborne microbes, aerosol particles and chemical vapours are permitted to remain. The controlled level of contamination is specified by the number of particles per cubic meter at a specified particle size. Clean rooms find applications where small particles can adversely affect the manufacturing process. They vary in size and complexity and are used extensively in industries such as research organisations, semiconductor manufacturing, pharmaceuticals, medical, aerospace, optics, military, etc..

  The key component of a clean room is the High Efficiency Particulate Air (HEPA) filter, used to trap particles that are 0.3 micron and larger in size. All of the air delivered to a clean room passes through HEPA filters, and in some cases where stringent cleanliness performance is necessary, Ultra Low Particulate Air (ULPA) filters are used. Persons working in cleanrooms are trained in controlling the contamination. They enter and exit the clean room through airlocks, air showers, etc. and they wear special clothing designed to trap contaminants, normally generated by human body. In clean rooms, technical arrangement is made to reduce the particulate contamination and also to control air parameters such as air temperature, velocity, humidity and pressure.

Air Conditioning

  Schematic diagram of a typical air conditioning (AC) system of a clean room is shown in figure 1. Chilled water from a centralised AC plant is used to chill the air and in turn to condense the moisture present. Pan humidifier and electrical heaters are used to maintain the required relative humidity (RH). Fresh ambient air is also chilled and added to meet the ventilation air requirement and the excess air gets out through small openings in the clean room. The air conditioned space is provided with false ceiling and chilled air enters through supply grille and there is separate duct for return air. The temperature of room air is controlled by the actuation of modulating valve to regulate the chilled water flow. Whenever the required conditions (say 23 ± 1 0C temperature and 55 ± 5 % RH) are achieved, the modulating valve will close and heaters will become OFF. Whenever the modulated valve is actuated (to reduce the chilled water flow), the chilled water is by-passed to the return line. Proper selection of blower will ensure that required air velocity is maintained inside the clean room for air circulation. Timely maintenance of air filters will ensure that strict dust level is maintained.

Figure 1: Schematic of a typical clean room.

Energy Conservation Opportunities

  The energy conservation opportunities in clean room applications are given below:

• The return air from clean room is hot and supply air is cold. Instead of using electrical heaters for RH control of chilled supply air, heat in return air can be transferred to supply air through a heat recovery wheel as shown in figure 2 and that much load on chilled water will also get reduced. The saving in energy will be enormous.
• Significant amount of power is being lost in transmission of power between motor and blowers. Now-a-days direct driven motor blowers are available with advanced controls for optimising the cooling load. Such systems need to be used.
• Conventionally, the air handling unit (AHU) filters are cleaned at some interval and some of the filters and chilled water coil fins are chocked. It is suggested to have 20-25 numbers of air filter panels of AHUs as stand by. The chocked filters need to be replaced (once in 2-3 weeks) with stand by ones. After washing, the clean filters may be used on next AHU and the process may be continued. This will improve the cooling performance of AHUs and avoid chocking of chilled water coils and to increase the life of AHUs. 
• Removing the air filters, the chilled water coil fins (in front of the blower) need to be inspected. The dirt between the fins needs to be cleaned with either compressed air or water jet from inside the AHU (opposite to normal air flow) so that dust and gel like substance is removed. It may be ensured that torn / damaged air filters are not used. If filters are cleaned in time, these things do not happen and performance & life of AHU is increased.
• Unnecessary heat generating loads (like UPS, photocopy machine, etc.) inside clean room needs to be shifted out to non-AC rooms.
• The efficiency of blower needs to be estimated based on the air flow rate, pressure developed and power drawn and if the efficiency is below 40 %, it needs to be replaced with high efficiency one.
• Replacement of three way valve of modulating motor with two way valve will lead to energy saving if variable frequency drive (VFD) is used with chilled water pump.

Figure 2: Schematic of typical heat recovery based RH control system

Conclusions

  Clean rooms find applications in many Industries and a detailed system study and analysis will lead to identifying all potential areas for energy conservation. Many such opportunities are described in this article.

---

Source: http://coolingindia.in/blog/post/id/14689/energy-conservation-in-clean-room

Clean Indoor Environment

Natural ventilation is the process of supplying and removing air through an indoor space by natural means, meaning without the use of a fan or other mechanical system. It uses outdoor air flow caused by pressure differences between the building and its surrounding to provide ventilation and space cooling. The use of natural ventilation is definitely an advantage with the raising concerns regarding the cost and environmental impact of energy use. Not only does natural ventilation provide ventilation (outdoor air) to ensure safe healthy and comfortable conditions for building occupants without the use of fans, it also provides free cooling without the use of mechanical systems. When carefully designed, natural ventilation can reduce building construction costs and operation costs and reduce the energy consumption for air-conditioning and circulating fans. An additional bonus is that no longer will any noisy fan be of your concern.

  Natural ventilation is very common in India. Even in the Mughal period when gross domestic product of India was one-fourth of the world economy, natural ventilations were widely used. It can be well understood from the design of Hawa Mahals where corridors are set in such a way to allow a high rate of air infiltration inside the building and ensure passive cooling in the same. However, with the advancement of technology, cooling systems were confined to refrigeration and air-conditioning. The underlying principal in these cooling systems is the Clausius statement of 2nd law of thermodynamics. According to the law, power input is required to run these cooling systems since in these systems heat is transferred from low temperature to high temperature body. For the sake of convenience, a heat engine can be coupled with refrigeration system for power input. In that heat engine heat is mostly supplied by burning fossil fuel which causes disturbance to the environmental harmony. Not only this, it is very difficult to find eco-friendly refrigerant. Commonly used refrigerants are being phased out as they are highly responsible for global warming (greenhouse gas) and ozone layer depletion. Considering these problems in active cooling, passive cooling through natural ventilation of wind is highly required to maintain harmony with nature.

  There are basically two types of natural ventilation that can be employed in a building: wind driven ventilation and stack ventilation. Both of which are caused by naturally occurring pressure differences. However, the pressure difference that causes wind driven ventilation uses the natural forces of the wind whereas stack ventilation is caused by pressures generated by buoyancy as a result in the differences in temperature and humidity. Hence, there are different strategies in the optimization of the two types of natural ventilation.

Stack Ventilation

  Buoyancy ventilation can be induced by temperature (known as stack ventilation) or by humidity (known as cool tower). Most commonly used is the stack driven ventilation. For stack ventilation to work properly there must be a temperature difference. As the warm air (usually given off by the occupants and their computers), which is less dense, in the building rises, the cooler air is sucked from the openings below. Design considerations for stack ventilation are (i) inlets should supply air low in the room. Outlets should be located across the room and at high level, (ii) the vertical distance between the inlet and exhaust openings should take advantage of the stack effect, (iii) use skylights or ridge vents and (iv) the function as fire exits of enclosed staircases should not be compromised if stack ventilation is incorporated into the design. With stack ventilation, it does not rely on the wind. On hot summer days with no wind, the naturally occurring stack effect can take place with relatively stable air flow. Moreover, because it does not rely on the pressure and direction of the wind, there is a greater control on locating the air intake. However, stack driven ventilation is limited to a lower magnitude than wind driven ventilation. It is also very dependent on the inside and outside temperature differences.

Figure 1: Map of India with three different wind roses in coastal regions

Wind Driven Ventilation

  As naturally occurring wind blows across a building, the wind hits the windward wall causing a direct positive pressure. The wind moves around the building and leaves the leeward wall with a negative pressure, also known as a sucking effect. If there are any openings on the windward and leeward walls of the building, fresh air will rush in the windward wall opening and exit the leeward wall opening to balance and relieve the pressures on the windward and leeward walls. Capturing the wind and bring ventilation to the building depend on the building shape, building orientation and location, building form and dimensions, window typologies and operations, types, shape and size of openings, construction methods and detailing, external elements, urban planning consideration, etc.

Wind Speed and Availability

  India is a tropical subcontinent which has larger coastal regions. In these regions, wind flow is highly induced due to differential heating of land and water. In these coastal regions, lots of villages are also situated especially in the states of Orissa, Andhra Pradesh, Tamil Nadu and Kerala. In these villages there are many hut like structures where natural ventilation can be provided by the proper setting of the window. Obviously, wind speed plays a major role in natural ventilation. From the view of human comfort wind speed should neither be very large nor very low. Best wind speed ranges for passive cooling is the wind speed for breeze which varies from 2-8 m/s. Now the question is the availability of this wind speed range in that particular location. Wind speed is highly location specific. Even in a particular location wind speed greatly varies in different months. To determine availability of a particular wind speed range, an availability factor can be defined which can be equated to the probability of occurrence of wind speed in the particular range for that location. The prerequisite of determining availability factor is the measurement of wind speed in each hour. India has a large network of meteorological stations controlled by Indian Meteorological Department (IMD) which measures hourly mean wind speed data in each of twenty-four hours of a day and 3 sec gust wind speed data. However, wind zone map of India is based on 3 sec gust wind speed data in which India is divided into six zones and basic wind speeds on the basis of peak gust wind speeds have been determined which vary from 33 to 55 m/s. The map is very much useful for specification and codification of design wind load on structures under extreme wind conditions. However, for wind induced natural ventilation parent wind climate modeling is of greater importance. For this purpose it is required to understand the measurement and analysis of hourly mean wind speed data. Hourly mean wind speed is measured at a height of 10 m by dyne pressure tube anemograph. It is measured in the last 10 minutes before the completion of the full hour and the last 10-min mean is considered as hourly mean wind speed. Though wind speed data is non-stationary, they can be converted into independent and identically distributed data (iid) by carrying out time series analysis and removing trend as well as white noise from the data. After converting wind speed data into random data, they can be modeled by a suitable probability distribution. It has been observed that wind speed probability density distributions, especially for the coastal regions, are highly skewed. Hence, normal distribution may not be an appropriate choice for wind speed data modeling. For this purpose, Weibull, Log Normal and Exponential distributions can be used. The availability factor can be determined by integrating probability density distribution within the appropriate wind speed range.

Figure 2: Wind rose of Ahmadabad

Wind Direction and Wind Rose

  Apart from wind speed, wind direction also plays a crucial role especially in corridor setting. Wind rose is required for this analysis. Wind rose can be defined as the pictorial representation of wind direction from which fraction of time for a particular wind direction can be determined. Three typical wind roses are depicted in Fig. 1. For better clarity, the wind rose of Ahmadabad is depicted in Fig. 2 below. It helps in determining the most favorable wind direction of a particular location and accordingly, corridors can be oriented. It is also equally necessary to fit wind direction data into suitable statistical models such as two-component and four-component von-Mises distributions.

Wind Circulation and Corridor Setting

  After orienting the corridor according to wind direction, inside circulation can also be provided. When wind flows over a bluff body, at the back of the same vortices are formed due to adverse pressure gradient and subsequent boundary layer separation. At the sharp edge also where the gauge pressure is negative, circulation occurs widely and the same also occurs at the front of the object mildly due to distortion of the stream line. This phenomenon of fluid mechanics can be used to provide natural circulation which is depicted in Fig. 3.

Figure 3: Wind Induced Circulation

  Now-a-days due to global warming and high level of pollution, atmospheric boundary layer changes which would lead to the change of the wind climate. The aerosols in the air also increase drastically which also absorb solar radiation. As a result, temperature increases but the irradiation on the surface of the earth becomes gradually less which would in turn affect the pressure gradient and wind flow. Hence, it may not be possible to predict wind speed and direction from probability distribution without considering the effects of climate change. Therefore, it is also required to determine the long term trend of wind speed and direction for proper predictions of the same.

Design Strategies for Natural Ventilation

  As shown in Fig. 4, wind and stack action combined yields best circulation and hence the design for natural ventilation should incorporate maximizing both the wind and stack driven ventilation design concepts. General design considerations include: (i) Increase air supply intake by ensuring no outside obstruction (such as vegetation or site objects) nor inside obstruction (such as furniture and interior partition) obstruct inlet openings; (ii) Rooms should have inlet and outlet openings located in opposing pressure zones. This can include openings on the windward and leeward walls or on the windward wall and roof; (iii) All occupied spaces should have an inlet and outlet opening in which at least a minimum of one opening should be an operable window to control flow; (iv) Inlets should supply air at a location low in the room. Outlets should be located across the room and at a higher level; (v) The long facade of the building and the majority of the openings should be should be directed so that the windward wall is perpendicular to the summer wind; (vi) Use skylights or ridge vents. They are very desirable for night time thermal comfort in houses to vent heated/warm air that rises, and allow heat to be radiated into the cold. It is also can be a good outlet for wind driven ventilation; (vii) At least 3m allowance for the floor to ceiling; (viii) window areas should not be excessive and be protected by exterior shading devices; (ix) Design for high thermal capacity and exposed ceilings for night cooling; (x) Reduce the possibility of wall warming by the sun through use of light-coloured building exteriors, trees/shrubs to provide shading and evaporative cooling, grass and other groundcover to keep ground temperatures low, and ponds and fountains to enhance evaporative cooling; and  (xi) Internal loading should be kept low. Many of the considerations taken above is to either increase the air flow or lower the heat gain so that the natural ventilation can effective cool the spaces in the building.

Figure 4: Distribution of Inside and Outside Pressures over Height of Building

Unique system of “natural ventilation” in Lotus Temple of New Delhi is based on the principles of ancient buildings ventilation. Image for representation purpose only

Clean Indoor Environment

  Outside air may contains unacceptably high level of pollutant including ozone, pollen, carbon monoxide, particulate matter, odors, toxic agent, etc. Hence, the filtering of incoming air is required to get clean environment, which is very essential for comfort and health. The type and number of filters are generally dependent on clean room applications. The main filter groups include: (1) filters for removing solid and liquid particles (viscous impingement and dry screen available in renewable, cleanable and throwaway variations, fibrous, electrostatic and air washers); (2) filters for removing gases and vapors (e.g. activated carbon and chemical filters); (3) filters for removing bacteria (e.g. ultraviolet or germicidal lamps). Apart from air inlet, the pollutants may enter in the air conditioning space with occupancy also and hence they are required to enter and exit the cleanroom through airlocks, air showers and/or gowning rooms, and they must wear special clothing designed to trap contaminants that are naturally generated by skin and the body.

Conclusions

  Efficient cooling systems are highly required but in harmony with nature. In most of the cases, traditional cooling systems cause harm to the environment and also human health. Hence, the passive cooling system through the natural ventilation of wind can be considered as a holistic solution in place of traditional cooling system. However, large uncertainties are involved in the availability of the desired wind speed range. Climate change can also influence both wind speed and direction. Accordingly, corridors should be oriented for passive cooling and many design strategies discussed in this article have to follow. As the outside air contains large amount of dust and pollutants, the proper filtering system is needed to get fresh air.

---

Source: http://coolingindia.in/blog/post/id/14697/clean-indoor-environment

Clean Room Devices & Technologies

A room in which the concentration of airborne particles is controlled, and which is constructed and used in a manner to minimise the introduction, generation, and retention of particles inside the room and in which, other relevant parameters, e.g., temperature, humidity, and pressure, are controlled as necessary, is called a Clean Room. This is a precise description of Clean Room.

Clean room for industrial segment

  The cleanroom is a modern phenomenon. Although the roots of cleanroom design and management go back for more than 100 years. Need for a clean environment for industrial manufacturing is a requirement of modern society. Clean rooms are needed because people, production machinery and the building structure generate contamination. As will be discussed later, people and machinery produce millions of particles, and conventional building materials can easily break up. A cleanroom controls this dispersion and allows manufacturing to be carried out in a clean environment.

  A major user of clean rooms is the semiconductor fabrication industry, where processors are produced for use in computers, cars and other machines. Micro particles can cause an electrical short circuit and ruin the semiconductor. To minimise contamination problems, semiconductors are manufactured in clean rooms with very high standards of cleanliness.

Clean room for hospitals

  The table shows manufacturers who require the absence of micro-organisms, as their growth in a product (or in a hospital patient) could lead to human infection. The healthcare industry is a major user of cleanrooms, as micro-organisms or dirt must not be injected or infused into patients through their products. Hospital operating rooms also use cleanroom technology to minimise wound infection.

What is cleanroom technology?

  As can be seen now, cleanroom technology can be divided into three broad areas. These areas can also be seen to parallel the use of the technology as the cleanroom user moves from firstly deciding to purchase a room to finally operating it.

Two types of clean rooms are popular

1) Conventionally Ventilated
2) Unidirectional Flow Type

---

S. D. Bandal is E&T/C Graduate Engineer from COEP, Pune

Source: http://coolingindia.in/blog/post/id/10022/clean-room-devices---technologies

Good Indoor Air Quality Makes Life Better & More Comfortable

Although we like to be outdoors as much as possible, people still spend an average of 85% to even 90% of their time indoors -- in schools, on the working floor, in offices, but most of all in our own houses or apartments. Therefore, it is of utmost importance to take into account these aspects that influence the inner climate, such as fresh air. As the interest in insulation and airtight construction is growing, the importance of a good ventilation is also increasing. Air circulation, replacing polluted indoor air by fresh outdoor air, leads to a healthy and comfortable indoor climate. A topic to really think about. 

  Each day, the indoor air is polluted by a number of sources; occupants (breathing, sweating), their activities (cooking, showering, heating, smoking, …), but also by the building itself and its furnishing (radon, volatile organic compounds, paint, glue, varnish, detergents, …).

Do you know, that …

• a new building has 3000 to 5000 litres of humidity, which has to disappear and that humans during normal activity produce about 1 litre of sweat every day? 
• if the humidity is over 75 % for more than 72 hours you will have mould in your house. 
• the number of dust mite increases exponentially with the increase of the humidity and that this is the main reason for allergies.
• the concentration of all these pollutants indoor can be 2 to 5 times worse than outdoor levels, occasionally even much higher.
• the CO2 level in an average room will reach the unhealthy level in 3 hours if the room is not ventilated adequately.
• radon is the most dangerous radioactive gas and it is widely found in houses.
• we do not see these pollutants, but they are there and they have an impact on our health if we do not take the necessary actions to get them out of our buildings. 
• 16 % of all heath spending is related to the air quality!

  With an increasing trend towards airtight construction, there are problems with humidity, CO2 and various other substances staying inside the home as adequate ventilation is not considered. As a matter of fact, excessive insulation and inadequate ventilation create a dead and stale air which accumulates mites, molds, viruses, bacteria, as well as moisture and harmful chemicals. It has been proven that breathing larger amounts of these pollutants for even the shortest period will affect our health. This may cause health problems (irritation of eyes, nose and throat, headache and sickness, among other issues) as well as comfort problems (smells, condensation, moisture). This is why we must regularly and properly ventilate our buildings, using demand controlled ventilation.

How to ventilate?

  Humans do need about 20 m³ of fresh air to feel well. Fresh air, full of oxygen, gives us energy, improves concentration and avoids sleepiness. In the past, ventilation was not an issue, as most of the old buildings had their own ‘natural’ ventilation through cracks in the construction. Today, our houses and other buildings are constructed as airtight as possible and architects and builders need to include elements, guaranteeing the indoor air quality is not poor.

  Many people still believe that opening windows from time to time is sufficient. However the effect of openings windows is only temporary and ventilation through open windows is uncontrollable and, therefore, wasting energy. In addition, they lead to other problems, such as noise, the risk of burglary, the intrusion of insects, …. Many buildings are also equipped with air-conditioning systems. People or building operation and maintenance companies are, however, setting these airconditioners with energy savings, which means they are just recirculating already cooled air, without combining it with fresh outside air. As a consequence, the pollutants concentrate inside the room. A controlled ventilation, 24 hours a day, is the only effective and secure solution to obtain a good indoor air quality and a healthy inner climate.

The A, B, C(+), D of ventilation

  In general, there are 4 different ways of ventilating, all of them based on the same three principles:

• The supply of fresh air in the dry rooms, such as living room, sleeping room, ….
• The drive of air through the dwelling via halls by means of louvres in the doors.
• The extraction of filthy air in the wet areas, e.g. toilet, kitchen, bathroom, ….
  These ventilation systems are classified by the way the air is supplied and extracted.

A. Natural supply and extraction

  The most easy and cheap way of ventilating, which does not always respect the standard. The circulation of air happens in a natural way based on the differences in pressure. The air enters the dwelling through adjustable openings in windows, walls or the roof. These openings are adjustable as they can be opened or closed just a little bit. In this way you can prevent the ventilation to go in overdrive during windy days. Some of these openings are self-regulating, which means they determine the volume of supplied air depending on the weather. Slits under doors allow the air to circulate through the dwelling, ending in the wet rooms, where it is extracted in a natural way by means of adjustable extraction openings.

B. Mechanical supply and natural extraction

  Using ventilation system B, the fresh air supply happens mechanically and the air is circulated throughout the dwelling via integrated ventilation channels. The mechanical supply of air results in a so-called chimney effect, resulting in the automatic extraction of air in a natural way. Combining a mechanical supply and a natural extraction, this system can be used to ventilate in a correct way in loud areas or in places where smells can appear. This supplied air can be directed through a filter before entering the dwelling. This kind of ventilation is however barely used in dwellings. Why? The answer is simple: the ventilators of the system are constantly using electricity. The system cannot be stopped and is therefore less interesting than a demand-controlled ventilation system C+ or D.

C. Natural supply and mechanical extraction

  This is a system, which can be easily integrated in new builds and renovation. The installer only has to integrate a minimum of ducts and apart from the regular maintenance of the extraction louvres and the self-regulating window vents no further maintenance is needed.

C+. Natural supply and demand-controlled extraction

  The difference between C and C+ is the demand-controlled extraction, using modulating extraction louvres. The ventilation level is adapted based on the way of living. As the ventilation level is never higher than really needed, energy consumption can be minimized. This kind of systems use a central extraction unit, combined with extraction louvres in the various wet rooms.

  Ventilation system C+ combines the constant supply of fresh air through self-regulating vents and the transit via door grilles with the extraction on-demand of polluted air in the wet as well as dry rooms thanks to a central extraction unit Healthbox. This unit has a powerful motor with control modules that can ensure proper ventilation of any connected room at all times. Dynamic sensors measure the extraction air in both the wet and the dry rooms 24 hours a day on CO2 or humidity and/or VOCs and adapt the ventilation level to the needs of the residents in an intelligent way. In this way, the Healthbox® makes a healthy indoor environment possible. Thanks to a new integrated technology, the polluted air is not only extracted in the wet rooms, but also in the sleeping rooms, which is very important to have a good air quality during sleep.
 

  This technology ensures that the house is optimally ventilated according to the residents’ activities. As a matter of fact, you can have ventilation controlled within the rooms the residents are most present. When they are watching television, the extraction level is raised in the living room. When they go to sleep, the extraction in the living room is decreasing and more polluted air is extracted in the sleeping rooms. Result: RENSON® developed a system that follows the residents and guarantees an optimal air quality in the house.

  The supplied air in this setup is not heated. In order to prevent draughts it is better to use self-regulating window vents. The more wind, the more the valve is closing, resulting in the same volume of air supplied at all times. When you are living along a road with a lot of traffic, you can use acoustic window vents. In this way, fresh air is supplied without having problems with disturbing noise.

D. Mechanical supply and mechanical extraction

  System D is based on the mechanical supply and extraction of air by means of ventilators. Both the supply and extraction can be controlled, but you need to have a double duct net: one for the supply in the dry rooms and one for the extraction in the wet rooms. In most cases, systems with heat recovery are used. The supplied air is then heated using the warmth of the extracted air. This system has its advantages in some cases, but is also more expensive as you need to have more ducts and you have to take into account the maintenance and change of filers on a regular basis in order to prevent health problems.

Special focus on demand controlled ventilation (DCV)

  Demand controlled ventilation (DCV) allows air to be circulated according to a building’s use and occupancy. DCV uses sensors to monitor and measure ambient conditions and feed real-time data back to a controller, which adjusts the fan speed modulating the ventilation rate to match the use and occupancy of the building. In this case, ventilation rates are kept to a minimum when nobody is the building or in a specific room. The ventilation is increased when people are entering a specific area of the building. This results in a good air quality in every room of the building and reduces energy in a significant way.

  Just an example: if people get up in the morning, they first go to the toilet. The clever sensors of the ventilation system notice someone entering the toilet and immediately increase the ventilation level in the room. When the occupants of the building move from the toilet to the bathroom taking a shower, the ventilation system will detect the increase in humidity and automatically adapt the level of ventilation in both rooms. In the end, when people are going to work, the ventilation will be reduced to a minimum.

  Today, demand controlled ventilation can even be extended to the bedroom. As the sleeping rooms are seen as dry rooms, in a normal setup only supply of fresh air is integrated, no extraction. The new technology adds extraction to the bedroom, because during the night people are creating a lot of filthy air, reducing the air quality in the room. By extracting bad smells, humidity and other pollutants out of the bedroom, people are guaranteed a good and healthy rest during the night, increasing activity and improving life quality during the day.

---

Credits: RENSON®

Source: http://coolingindia.in/blog/post/id/11392/good-indoor-air-quality-makes-life-better--more-comfortable

Need for Smart HVAC Control Systems

Controls for heating ventilating and air conditioning cover a broad range of products, functions, and sources of supply. Controls are the starting stopping or regulation of any heating, ventilating, and air conditioning. The application of HVAC controls starts with an understanding of the building and HVAC systems, and the use of the spaces to be conditioned 

and controlled. The type of HVAC system determines the control sequence. Several types of control products such as pneumatic, electric, analog electronic, or electronic direct digital control are available.

     At one time, draft dampers followed by thermostat control of the dampers controlled heating. The use of mechanical stokers for coal firing required another step in the use of control. When oil burners were introduced, the concept of combustion safety control became necessary. This involved the sensing and proof-of-flame in the proper time sequence of introducing draft, fuel, and ignition.

     The use of steam and hot water radiators led to the concept of zone control and individual room control. Forms of zone control included closed loop control using zone thermostats and open loop control with outside conditions setting the rate of heat delivery to the zone. Both of these forms of control were used to regulate the delivery of heat. The means of regulation included the following: Valves to control the flow of steam or hot water, controlling pumps to circulate hot water, and controlling boiler operation. When IRC was used the central supply was maintained and radiator valves were controlled by room thermostats. The use of fans to deliver ventilation as well as heated air was controlled by dampers, which varied the source and volume of air. The typical control of unit ventilators was by pneumatic controls and included the following features: minimum outside air, discharge air, low-temperature lim, and thermostats with lower night settings activated by compressed supply pressure level. The increased usage of air conditioning led more complex control sequences in larger systems to central monitoring and control.

     The development and use of computers and microprocessors has caused great changes in the HVAC controls industry. Minicomputers were installed on jobs to collect data to provide centralised control. Then, microprocessors were used for remote data-gathering panels to gather data – and provide direct digital control. Computers are now used as on-site central controllers with operator interfaces and as computer assisted engineering tools in the design of system programs, databases, and documentation. Microprocessors are still used in remote data gathering, yet also in small unit controllers and in smart thermostats.

     HVAC systems are classified as either self-contained unit packages or as central systems. Unit package describes a single unit that converts a primary energy source of electricity or gas and provides final heating and cooling to the space to be conditioned. Examples of self-contained unit packages are rooftop HVAC systems, air conditioning units for rooms, and air-to-air heat pumps.

     Central systems are a combination of central supply subsystem and multiple end use subsystems. End-use subsystems can be fan systems or terminal units. If the end use subsystems are fan systems, they can be single or multiple zone type. With central systems, the primary conversion from fuel such as gas or electricity takes place in a central location, with some form of thermal energy distributed throughout the building or facility.

     There are many variations of combined central supply and end use zone systems. The most frequently used combination is central hot and chilled water distributed to multiple fan systems. The fan systems use water-to-air heat exchangers called coils to provide hot and/or cold air for the controlled spaces. Another combination central supply and end use zone system is a central chiller and boiler for the conversion of primary energy, as well as a central fan system to deliver hot and/or cold air. The multiple end use zone systems are mixing boxes, usually called VAV boxes. The typical uses of central systems are in larger, multistoried buildings where access to outside air is more restricted. 
Typically central systems have lower operating costs. Besides packaged unitary and central systems, there are a variety of special-purpose systems. These include the following:

• Heat pump cycles on chillers that use rejected heat or tower cooling.
• Thermal storage.
• Cogeneration of electricity and heat.

     Basic control regulates the amount of heating or cooling necessary to meet the load in conditioned spaces. Minimum outside air needed for ventilation is provided whenever a space is occupied. When outside air temperature is a suitable source for free cooling, it is controlled as needed at values greater than the minimum.

     The approach in packaged unitary equipment is to control the generation of heating or cooling by space thermostats. The approach in central systems is to control the delivery of heating and cooling by the end use zones to match the load in the space. The supply is controlled to match the load imposed by all the zones. A typical method of doing this is for room thermostats to control zones, and discharge controllers to control central supplies. Discharge temperature controllers control the rate of primary conversion of chillers or boilers, and pressure controls determine the delivery rate of the pumps or fans distributing the central supply. In many cases, there are multiple boilers and/or chillers and pumps, which are put on or off line as necessary to provide proper capacity. Those online are modulated as necessary to meet load needs. The controls to put units online and off-line would normally be applied to meet the system needs.

     Direct digital control, is sometimes used to describe everything a computer or microprocessor-based control system does. The original use of the term signifies closed-loop control of local loops by a digital computer or microprocessor.

     Energy management application programs are different than local loop control – and are named for their specific functions, such as start or demand control. The considerations of which energy management application programs should be used rely upon the type of building and HVAC system. For instance, optimum start-stop programs are not appropriate for a hospital that has 24-hour operation. Load reset of supply temperatures is appropriate for systems that supplying heating and cooling simultaneously, such as reheat systems or hot and cold deck mixing box systems.

     The concept of optimising control is not only to control space conditions, but also to do it in a manner that minimises the energy and costs when different forms of energy are available. An optimising strategy is generally to improve the efficiency of primary supply equipment or to reduce the losses of energy in end-use systems. The sizing of equipment is to meet maximum loads, but the equipment is usually run at less than maximum load. This means that the part load characteristics of the equipment determines the efficiency in meeting a given load.

     When there are multiple chillers or boilers, an optimising strategy would be to choose the most efficient equipment, which has the capacity to meet the load at any given time. Also, with some types of end use systems, energy wasted by bucking heating against cooling can be minimised by resetting supply temperature levels to be no more than that is necessary to meet a given load condition. Another way to optimise is to use the thermal storage of a building to make use of energy stored at low cost and used when needed. Moving heat from one area of a building to another can be an optimising opportunity as well.

     These optimising principles are used for specific types of HVAC. The variable in all of these circumstances is the amount of heating or cooling load and the control action to make some change in the way a load is supplied. This process has led to the use of the terms load reset and dynamic load control to describe this general approach to optimising control. The selection of the most efficient combination of chillers to supply a cooling load has been called optimised chiller selection.

     Before World War II, the main suppliers HVAC controls in commercial buildings were companies that promoted pneumatic controls. The predominant idea at that time was that controls for commercial buildings were too complicated to sell over the counter – and had to be installed and supervised by the controls manufacturer. This concept included having branch offices with installers and service people.

     Electric control systems for commercial buildings were modulating type controls. They were sold on a supervised basis. When several other companies entered the commercial controls market with electric and electronic controls, some of their distribution was through distributors and branches. Some of the newcomers, who started with electric and electronic controls, expanded into pneumatic controls – either by their own development or by association with foreign companies.

     When computer-based supervisory control systems came to market, some larger companies with computer-based products entered the HVAC controls market; but eventually gave up. As international business developed and companies became multinational, some foreign-based controls companies expanded into the U.S. markets directly or through associations with smaller U.S. control companies. During the 1970s, some small companies evolved with limited product lines for energy management functions. When DDC became accepted, some small companies developed microprocessor- based DDC controllers and supervisory systems.

     The full line control companies that started out as major players currently remain as major players – but with more competitors that have limited systems. Some major HVAC systems manufacturers have acquired or developed control capabilities. They market packaged HVAC systems with controls and supervisory control systems. Some companies provide products for specific applications. The selection of a source of supply should consider the life cycle needs and costs as well as the track record of suppliers.

     The mounting of room thermostats and room humidistats has been the subject of much discussion, and for many years the industry standard has been for the thermostat to be mounted near the door of a room 5 ft from the floor. The problem is that if the room is full of children, the thermostat is not controlling the temperature where the occupants are.

     It's important to study the location of the room thermostat or humidistat as to the effect of conditions at the thermostat. Remember, the thermostat responds only to what is going on at its location. If there is a ceiling diffuser blowing air at the location where the thermostat is mounted, there is going to be cycling of the system.

     Sometimes, installers and others are concerned about the way thermostats and humidistats are mounted on the wall; that is, whether they should be mounted in a horizontal or a vertical position. Generally, aside from writing on the unit's face, either horizontal or vertical mounting is fine. There is, however, one important exception: when the thermostat is electric and has a mercury bulb switch contact. This type is common in residential and commercial buildings and requires the thermostat to be mounted a certain way. Some of these require the installer to use a level to mount it properly.

     Room thermostats and humidistats are devices that control automatic valves and dampers in a control system. These devices have built in sensors as well as moving parts that control the device. An example is a pneumatic thermostat that has a bimetalic sensor and a relay. Usually the complete package is under one cover on the wall, and all action takes place at the thermostat. There are, however, sensors that are mounted under the cover in the room that have no actuators relays under the same cover. They usually transmit the temperature information to another device at a remote location that does the controlling with relays, and so on. Normally, this principle is used in electronic control systems involving a wire wound resistor mounted under a cover, which reads the temperature in the space and transmits that information to an electronic controller in an equipment room.

     Often, there is confusion with the terms thermostat and sensor. The concept of a sensor under a cover in the room is new and came about because of the advent of electronic control systems. Room sensors are used with other control systems and are sometimes called transmitters. 

     In the case of pneumatic controls, the transmitters use a sensor and a special relay that transmits a pneumatic air signal proportional to the medium being sensed. An example is a transmitter under a room thermostat cover that transmits an air signal based upon the temperature being sensed in the room.

     The transmitter may look like a thermostat, but it does no controlling by itself, it depends upon a receiver controller in a different location to take the action on the controlled device. The dials of these devices are only used for calibration, and are not moved. These transmitters come in standard ranges and send out a signal based on the medium being sensed. 

     Thus, we understand that Building Automation & Control System plays a vital role in integrated building planning. The system provides energy savings, greater comfort, safety and better operational efficiency. In India, the rising concern for Greenhouse Gases along with rapidly increasing power demand-supply gap are contributing to the growing adoption of the automation & control systems in the buildings – through electronic security & safety, HVAC and lighting control equipment. Majority of the building automation solution & system integration companies, are focusing towards new buildings and not on retrofits. This is on account of higher energy saving potential in the new buildings. 

     According to India Building Automation & Control Systems Market Forecast & Opportunities, by 2019 the market of India Building Automation & Control System is projected to grow at around 21.7% during 2015-19. The demand for BACS systems is majorly driven by commercial building segment, due to increasing number of shopping malls, office buildings, educational institutes, hotels, hospitals, etc. 

     The market is further supported by mandatory regulation of energy efficiency in commercial buildings.The policy & regulatory support such as building codes, incentive schemes and labeling schemes such as LEED rating scheme and BEE star rating scheme are expected to continue driving the BACS market over the next four years. The market growth is further supported by emerging trends of cloud based energy control solutions, ESCO schemes and automated demand response in building automation system. With the huge growth in the technological advancement, fast technology, and accepting such developments by the consumers, the currently available HVAC Controls are smart in many ways. 
Environmental concerns have forced some government to make regulations, which essentially requires the use of smart HVAC controls. The Smart HVAC Controls systems are definitely more energy-efficient compared to the existing HVAC Controls, either by having sensors that can communicate to the thermostat or with the ability to access a home HVAC system over the cloud using a smart-phone application or a web browser. The concept of Modular Approach is also expected to play a vital role in Smart HVAC controls market.

     The market is segmented in terms of product type such as Temperature Controls, Ventilation Controls, Humidity Controls, and a mixture of two or more controls as an Integrated Controller to provide the required environment in a cost effective manner. Also, the smart HVAC controls report is segmented in terms of various components such as sensors, controllers, controlled devices, and smart vents. It is very important to differentiate the modes of operation of any smart HVAC controls, which otherwise are segmented by Wireless Controls, Programmable Controls, Weather Compensating Controls, and Remote Access Controls. The Smart HVAC Controls Market is further segmented according to Verticals which include: Residential and Commercial sector, and Geography which include:The Americas, Europe, APAC and Rest of the world. Various smart HVAC controls market trends such as Digital and IP Based systems, BACnet and LonWorks controls from major players like Honeywell International, Inc., Johnson Controls, Inc., United Technologies Corporation, Siemens AG, Daikin Industries, Lennox International, Hitachi, Ingersoll-Rand Inc., Schneider Electric SA and Emerson Electric Company.

---

Norman Dsouza,Sales & Marketing Director, NewkemEngineers Pvt. Ltd.

Source: http://coolingindia.in/blog/post/id/8457/need-for-smart-hvac-control-systems