PART-001: Basic Concept of Heating Ventilation and Air-Conditioning (HVAC)

I am starting a series of blogs for explaining important HAVC (Heating ventilation and air-conditioning) concepts into simple language. Theoretical knowledge we all can gain from books. But for practical knowledge we have to work hard in our field. I have 12 years and counting experience in HVAC industry. Thus, I will focus more on practical aspect of HVAC. If you find it interesting please like, comment and share the blog to keep me motivated. We all need motivation. Without constant motivation we lose interest and stop doing whatever we started. All type of questions based on the current topic are welcome.

Today, I want to discuss about aspect ratio in ducting. What is it and how is it so important?


Aspect ratio is very simple term. It is the ratio of two sides of duct, i.e. height: width. We consider 1:4 as maximum acceptable aspect ratio as per standards for rectangular duct. It is always better to have lower aspect ratio up to 1:1, if space permits. That means square duct. As aspect ratio increases, friction to air flow increases and thus cost of fan too increases. Similarly, cost of material also increases with increase in aspect ratio. Because thickness (gauge) of GI sheet (or any other duct material) used for duct-work depends on the size of duct. If you increase one side of duct, thickness of sheet will increase after specified size. As we move from square to rectangle, surface area increases. Increase in surface area increases duct heat loss. Furthermore, insulation material is increases because of increase in surface area.

Though, aspect ratio looks like very trivial term, but cost wise it plays very important role. Therefore, always keep aspect ratio in range of 1:1 to 1:2 and maximum up to 1:4 which is acceptable in case when there is no enough space to install the duct. In all such conditions you are supposed to re-calculate the ESP of fan before making decision to change the size. It is interesting to know that how ESP of duct and Aspect ratio are connected. For simplicity, equations of friction loss are derived for round duct. Thus, first we must calculate equivalent diameter for all rectangular ducts. Formulas are available in carrier hand book-chapter 2. Now, as aspect ratio increases, equivalent diameter decreases for two duct with same cross section area at constant air flow. Friction loss of duct is inversely proportional to the equivalent diameter for constant flow. Hence, friction loss increases with increase in aspect ratio for same air flow. 

There is one big misconception about re-sizing of duct when we have to avoid any obstruction like structural beam. Most of people increase width and reduce height, keeping cross section of rectangular duct same. This is a wrong practice. Keeping cross section area same does not mean that velocity and pressure loss will remain same. The correct practice must be to first convert rectangular duct by calculating equivalent diameter.

Equivalent Diameter Deq= 1.3 ((a.b)^.625 / (( a+b)^.25) )

Where, a and b are sides of duct.

Now, check from chart, for same equivalent diameter what rectangular duct sizes are available from ASHRAE or Carrier. Use any of those rectangular size which keep equivalent diameter same. It will keep velocity and pressure drop same even after reducing the height and increasing the width.   


Basic Information about Air-Conditioners (AC):

  • Type of AC : Window and Split?

Choice of AC depends on your comfort and room location. Window AC’s are cheaper than Split ac. Split AC consists of separate indoor and outdoor units thereby called split ac. Since it has separate outdoor unit consisting of Compressor and condenser, indoor unit is very quiet. Split ac are more decorative and comes with many filters.  If you want quite ac with aesthetic looks go with split ac. But if you have a window in your room or a wall which open to outside, you can go with window ac. Since window ac is a single unit incorporating all components including compressor, it makes more noise. Normally window ac are available upto 2.5 Ton because above that, their noise became unbearable. Consequently, for higher capacity you have to go with split ac. 5 ton and above split ac comes in floor mounted model.

If you are a middle class person or if you do not want to spend more on AC, window ac is good choice.

  • Inverter AC or Non Inverter AC: In Non inverter ac, compressor motor has two option-either on or off. Whereas in Inverter ac, motor can run at variable speed and thus saves electricity. Therefore, Inverter ac are good for power saving.
  • Refrigerant: Now, many companies stated shifting to CFC free, Ozone friendly refrigerant.  R410 was manufactured to replace R22. Now many companies are using R410 for their products. Previously R-22 was used in all the AC, but since it cause ozone depletion, it is being phased out by 2030. However, R-22 is more efficient refrigerant, but for environmental consideration, please go with Ozone friendly refrigerant. Companies like Godrej are befooling consumers by writing R-22 as eco-friendly. Most of refrigerant are ecofriendly, but we are concerned about Ozone here not ecology. Be careful. Say No to R-22 (Trade name Freon).
  • Compressor: Compressor is the heart of ac. Please read my last blog too for more information about different companies making AC’s by clicking here. Here I will let you know about different type of compressor. For small capacity i.e below 5 Ton, there are two type of compressor normally used: 1) Rotory. 2) Reciprocating.

Rotary compressor used less moving parts and thus need less maintenance. Reciprocating compressors are more rugged. For home AC, go with rotary compressor as they are more energy-efficient.

  • Some important terms: a) Ton or tonnage: In air-conditioning field, Ton is a unit of cooling not of weight. 1 Ton is defined as amount of cooling produce by melting of one ton of ice. The other unit for cooling capacity which is normally mentioned on AC unit is BTU/Hr. . One ton is equal to 12000 BTU/hr..
  • b) EER: Energy efficiency ratio: it is defined as the ratio of the cooling capacity (in Btu per hour) to the power input (in watts). Higher EER rating means the more efficient the air conditioner.



Check the Compressor Make before Buying an Expensive AC

Summer is approaching in India.The most important part in any AC is its compressor. Therefore, I was interested in knowing which brands are making their own compressors and which are using Chinese and western brand. Surprisingly most of the so-called Indian brands use Chinese components. Videocon, Onida & now Voltas and many more are manufacturing most of component in china including compressor. Below is the list of few famous brands in no specific order and there price (taken from each company website in Feb.2018):

1.5 Ton Window ac comparison
S.No. Brand Name Price *     (in Rs) Energy efficiency (ERR) Refrigerant Remark
1  Voltas by TATA (LZH series) 32,890 5 Star (3.32) R-22  
2   Onida (WA185FLT) 34,990 5 Star (3.42) R410A BTU/hr.=17401
3  Blue Star            (G-series) 30,000 5 Star R-22  
4  Videocon 37,500 5 Star (3.32) R-22  
5  Godrej 27,990 5 Star (3.4) R-22 7 Year compressor warranty
6 Samsung N/A N/A N/A Only split ac data found
7  LG 35,140 5 Star (3.36) R-22  
8  Hitachi (RAV518HUD) 37,090 5 Star (3.50) R-22 Quite operation, Compressor manufacturer
9  Carrier 34,000 5-Star R-22  
10  O-General 40,530 3-Star R410A Work up to 55 deg.C
* Price are taken from different websites and shown only for comparison.


First five are Indian multinational brands, and last five are International brand available in India. Because of price war with multinational companies, Indian brands also started manufacturing in China. The secrecy these companies maintain about component of their products is surprising. I checked many manufacturer websites and there brochures but did not find any information about compressor make and other major component manufacturing list. I expected little more transparency from companies.


Companies must have courage to tell the truth about their product to the costumers. Else, it is the duty of Government to save costumers from such fraud. Companies must be clearer about the manufacturing. They can use tag such as “Indian technology, assembled in China” or “Made in India with Chinese component”!

A costumer has a right to know what he or she is buying. When a company mention on a product: Made in India. It gives an impression that majority of components and whole assembly is done in India. If a customer has full information then he can make a better choice. For example: Very few companies are making compressors for their own AC’s, rest of all companies are buying compressors from other companies. When we want to buy an ac, we choose best brand thinking it will have best components and thus we are ready to pay more for it. But if I tell you that your selected brand and another cheaper brand both are using same compressor and cheaper brand is giving you better energy efficiency? Will you still buy the same brand?

Component make and manufacturing is one of the best-kept secret in ac market. Even sales man will not be aware about it. They will tell you about filters, remote control, dust control, exterior body, coil materials, evaporator fans etc. However, nothing about compressor except 5 year warranty. All compressors comes with 5-7 years warranty. Nevertheless, 7 years is not such a long time when it comes to home appliances. We want to use it for next 20 years. If one compressor will work for 5 years, you have to replace it 4 times in 20 years’ service!

One more surprising thing is refrigerant. Most of the companies still using R-22 as refrigerant. R-22 (Trade name Freon) contain CFC- a chemical causing Ozone depletion. Eventually, all the HCFCs have to be phased out by the year 2030 including R-22. Hence, if you are planning to buy an AC and expecting to use it for more than 10 years, make sure you do not buy AC with R-22 refrigerant. After 2030, price of R-22 will increase abnormally. It is better to make wise decision now.

To protect environment, let us shift to green technology and CFC free gases. R-410a and R407 are CFC free and does not cause ozone depletion. Buy inverter AC to safe electricity.

Internet: How it changed the World in last 25 years


Some Key Milestone:

September 2, 1969: First time two computers communicated with each other.

Oct 29, 1969: Message sent from computer to computer in different locations.

1971: The first email was sent.

Jan 1, 1983: ARPANET adopted the standard TCP/IP protocol.

March 1989: Tim Berners-Lee invented the World Wide Web.

April 22, 1993: Mosaic became the first web browser.

Till 1995, few entrepreneurs recognized the power of world wide web. But majority of world was still unaware of this giant monster called Internet.Those who recognized its power and future potential becomes some of the world richest business person in next 25 years. and are few enormously successful websites increasing their business ever since. As time passed by many new entrepreneurs started new companies to facilitate internet users like search engines. Larry Page & Sergey Brin founded Google in 1998. Today it is the largest internet company by revenue.

It is not just the internet but the vision, commitment and persistent hard work that make these companies what they are today. Nevertheless, Internet provided them powerful tool and platform to connect with the world. Jack Ma founder of Ali baba group, during various interviews keep telling people that when he started his business, no one knew about internet and speed of net was too slow. Most of the things were against him but still he continued with his vision. Today he is one of the richest man in China.

As Internet become famous, more and more companies join the bandwagon. After 25 years, presently internet connects more than a billion peoples around the globe. Almost half of the world population uses Internet. Internet becomes a symbol of development. More internet user means more developed region. Websites are increasing at exponential rate. Even though doing business on internet is becoming difficult because of international competition websites are increasing because of ease of starting and user-friendly website setup that too at low maintenance cost. WordPress and Wix are two examples of websites, which allows you easy setup of your website even without knowing web design and development.   

For small companies too, Internet has huge potential. With right kind of product and skill, they can cater needs of international market. One can display their products to whole world! You can also advertise on social networking sites in free or by paying money for advertisement based on CPC (Cost per click) or CPM (Cost per thousand impressions). If you are passionate about making Videos and sharing your experience and ideas, you can start your own channel on YouTube. If you find many viewers for your videos (more than 1000 views), you can monetize your channel and earn some money. Do not start any You Tube channel or any website with the sole intent of making money without being passionate about your work.

Internet is a great tool for education and learning too. All kind of educational stuff, books, online classes, videos and latest news are radially available on internet. As time will pass, importance of internet will increase further.  

The inhuman caste system

There are two concept of caste system in India. One that is practically existing and other that is theoretical. In Practical caste system, Society is divided into four main groups (with a fifth, “the untouchables,” outside of the caste system). Shudra are lowest caste below them are untouchable. Brahmans are the highest caste and they are the one who can read scriptures and perform rituals and Puja in temples. The Sanskrit word for caste is Varna. Manusmriti, widely regarded to be the most important and authoritative book on Hindu law and dating back to at least 3000 years “acknowledges and justifies the caste system as the basis of order and regularity of society”.

Small towns and most of the villages are still infected by this caste system. Lower caste peoples are treated in an inhuman ways. They are untouchable and can-not enter temple. Partially poverty and mainly religious belief make lower caste to accept such inhuman torture. Since centuries, they are living and suffering but never raise voice. Only after independence, and after government provided reservation for SC/ST and OBC, now we can see emergence of leadership in so-called lower caste.

Education played a vital role in reducing inhuman torture based on caste system. It is education, which pave the way for theoretical caste system, which eliminate hierarchy system based on birth from caste system. According to new system caste are based on work you performed and not based on your birth. The Varna system prevalent during the Vedic period was mainly based on division of labor and occupation. That means a Shudra can become Brahmin and a brahmin can become a Shudra based on their work. But this is only theoretical concept which is used to cover up evil of caste system. Truth is even in 21st century when we have abolished slavery entirely, there are peoples who still wants to maintain their supremacy based on caste and are forcing lower caste to live a miserable life.

Let us stop this age-old inhuman activity. Let us treat every human equal and make India strong.

An Open letter to TEEN-INDIA

Hi Mates,

Let me take some liberty to write in your language. :). Because it is always easy to make someone understand in his or her language. Here is my message to TEEN-India.

I am not a preacher. I am just like you-An Indian with some gray hairs and with a vision to make India developed Nation by 2030. Thanks to IT (information Technology) that you have all the information on your fingertips literally. Just a click on google and you find information about everything invented or discovered until this date. You are empowered to bring change in sleeping giant called India. So gear up guys and gals and be the change you want to see in our Nation. Start from yourself.

You are tomorrow’s entrepreneurs. So Work on tomorrow’s technologies. Work on AI, Block chain, AR, VR, edge computing, renewable sources of energy, space technology, Robotics, Genetics, synthetic biology, stem cell, Nano technology etc. Look around yourself, what problems Peoples are facing and how you can solve them using technology and convert it into a successful business idea.

What Hollywood movies shows you is not real west. In real west, large no. of peoples are dedicating life to research and development of Science. They publish most of the books and read them too. That is how they are so advance and developed nation. Someone asked Elon Musk (A man behind Space X and Electric car Tesla) “how do you know about so many things?” He simply answer in three words “I read books”. Here in India just a wink distract whole Nation! People will tell you that Bill Gates was a drop out. However, they forget to tell you that he used to study books for hours in his free time. Below is what Bill Gates told about his learning habit:

“I’ve always loved digging into the science and math behind my work. At Microsoft, I got deep into computer science. At the foundation, it’s computer science plus biology, chemistry, agronomy, and more. I’ll spend hours talking to a researcher or an expert, and then I’ll go home, dying to tell Melinda what I’ve learned. I can’t imagine a better way to spend the bulk of my time”: #TBT

Reading books, along with your textbooks, are very important for a better perspective of your life. Watch motivational and inspiration videos from all over the world. Learn about Great personalities, innovators and entrepreneurs across the globe like Jack Ma, Elon Musk, Richard Dawkins, Jeff Bezos, Sunder Pichai, Indra Nooyi , Steve Jobs, CV Raman, APJ Abdul Kalam, Aryabhatta , Galileo, Newton, Einstein and Stephen Hawking to name a few.

What India needs is a youth with scientific attitude towards life. An ignited mind. A desire to change corrupt systems and vote for right candidates. Start early. Do not just memories books for exams. Understand them. Believe that everything you are reading is important. Ask questions, try to understand practical implications of knowledge you are gaining. Apply what you learn in school in your daily life. Be an observer. Ask yourself can we do things differently. Find some innovative ideas and try setting up a business. Right now, we have fewer jobs and more qualified students searching for jobs. Hence, the only solution is instead for becoming job seeker become job creator. Govt. has introduced many schemes for starts up under Make in India initiative.

World is full of small and negative thinkers. If you are not getting good-grades in your exams that does not mean you are not genius. You might have some other skills or you are just not interested in studies. Your grades are not representative of your intelligence. Einstein never scored good grades in exam but still he is one of the most brilliant mind in human history. Believe in yourself. Don’t always listen to others. Sometimes we feel that everything is finish. We start thinking that I do not have any quality. I am a total failure and I am an embracement for my family. There is no point in living.  That is not true.

After every dark night, there is a bright day. We never know what our destiny holds for us. One or two failures does not end anything. Greatness is not in never falling, but in raising again every time you fall. You are not a failure until you give up! My friends NEVER GIVE UP. Pin point your problem that is holding you back. Work on it and get rid of it. Life is beautiful. Believe in yourself. One day you will succeed. You will have everything you dream about if you never give up. If you can’t run-Walk. If you can’t walk-Crawl. Nevertheless, never ever stop in your life. Always keep moving forward.

Wishing you happiness and success in all walks of life. Jai Hind.

A fellow Indian.

Facebook Down-Are you too having problem?

I though only I am having problem with facebook accessing. But it seems lot more people facing same problem. Facebook is taking lot more time in opening and most of the time it hang! Many more people are facing the same problem as can be seen on below link.

Please let me know in comment section if you have solution or if you too are suffering.


Artificial Intelligence (AI) and Machine Learning (PART-1: Introduction)


As we usher in new century, we entered a new world-a world of artificial intelligence. Though people were working on AI from last 50 years or so but only now we are able to see practical application and fast development in this area. AI is the simulation of intelligent behaviour in computers using programming. That means AI imitates human intelligence without emotional interference. Since the programming is based on lot of research data AI can perform better than human. AI machines beaten human in games like chess and Go. Silently they are entering our daily life. If you use iPhone you must be familiar with siri- an AI application.

Artificial Intelligence is still in developing stage. Yet many Peoples find it dangerous for human kind. Their intuitions might be right. There are two ways AI research can proceed in future. One is called slow takeoff and other is fast takeoff. A slow takeoff is a situation in which AI goes from sub-human to human to superhuman intelligence very gradually. We will have enough time to study dangers associated with it and to remove those dangers. But in fast take off in few years we will develop super artificial intelligence and that will not give us enough time to study, understand and restrict dangers associated with it. We can not predict behaviour of anything which is more intelligent than us. Presently all data suggest medium to fast takeoff because all big companies and developed countries are spending billions of dollars on it. Within ten years we might reached  singularity a term used for AI reaching human brain power.

Machine learning is another major part of AI. Learning without any kind of supervision requires an ability to identify patterns in streams of inputs. It is much more like how a baby learns to interact with world. I find it more powerful than AI based on programming every known thing. Because in that case you cannot expect more than what you input and intelligence of machine is dependent on programmer intelligence. If programmer is not careful enough, machine will make mistake. But in machine learning, based on sensors machine learn itself from its surrounding. It gives machine ability to learn from data without programming it explicitly. This process is slow but has more potential in long-term. We might be able to make a machine which can answer some of the ultimate questions which we can’t answer because of our limited capabilities.  Google Deep mind uses reinforcement learning and thus it can improve itself. Alpha Go made by Google deep mind division already beat human in Chinese game of Go which is much difficult than chess.

to be continued in Part-II

Cars fitted with Hydrogen fuel cell is better solution than Electric Vehicle in India :

Search for clean fuel for automobile took us to two different directions: one towards Electric vehicle which uses lithium-ion batteries and charging ports and another is hydrogen cell which use hydrogen from filling station. Both are clean solution. Electric vehicle has no effluents and Hydrogen cell cars produce water. But the most important difference is that for electric vehicle we have to first produce electricity using other sources, some of them may not be renewable like coal and thus still cause pollution. So basically we are just shifting problem from one place to another. In developing countries where we do not have enough electricity for 24 hours supply in cities forgets about villages, adding more consumption will be disaster. If electricity will be cheaper than petrol (which seems likely in few years) when use in automobiles, for economic reason people’s will buy electric vehicles. Electric cars are far better than combustion engine cars and have less maintenance. Thus there will be huge increase in demand of electricity in future. Big question is how we will manage the increasing demand of electricity when we are already short of supply?

Hydrogen fuel cell is the solution. Already many countries started using hydrogen fuel cell. It is a proven technology. Instead of electric charging station we have to build hydrogen charging station. No more infrastructures required! No burden on electricity production. No need of batteries. Japan is producing and paving the way for hydrogen cell vehicle. Japan, Germany and US are increasing hydrogen filing station. UAE also opened its first hydrogen filling station. Though this technology is expensive but is the real solution of pollution. With tie and more and more use of this technology it will become cheaper and better.

Digital India- A dream without the vision.

According to the 2011 census of India, 68.84% of Indians live in Total 640,867 different villages. These villages neither have permanent electricity nor do they have computers and smart phones. They simply cannot afford computers and smartphones because 30% Indian lives below poverty line and most of them are found in villages. They are uneducated and unlettered. They do not know whether they will get food tomorrow or not. They need good agriculture policies.

Government must start from building Infrastructure. First let there be electricity for more than 18 hours a day. Than bring network cables and mobile towers in all villages and connect them with internet, Schools, Banks, Hospitals and Roads. Once we have this basic infrastructure ready it will be the right time for starting “Pradhan Mantri Gramin Digital Saksharta Abhiyan”.

Will you give a windows software to someone who don’t have a computer? How about teaching villages about Mars mission or perhaps Artificial Intelligence? Will it work? I don’t think so. First make them literate. Improve standard of Government schools. Appoint more teachers. Don’t waste money in unproductive and unaccountable things like Digital Saksharta.

We have to be practical in our approach. We must move forward step by step. For that we need leaders with vision. Without that we cannot achieve any substantial growth. If we want to develop India we have to start developing villages. But villages are dependent on agriculture. So we have to provide latest technology related to agriculture like irrigation technology, information about fertilizers, high yielding seeds, information about soil, crop rotation, water harvesting, biogas and solar energy utilization.

Now question is how we develop villages? First, we have to complete electrification of villages. That means minimum 18 hours’ electricity in every village. To achieve this, we have to increase production of electricity. Which no government is doing. Till the last year officially there were villages without electricity. Now government has installed few solar panel here and there and claiming that all villages are electrified. Congratulations!

Second step must be quality education for all. We are really lacking in it. Government schools in villages are becoming worst place for education except few exceptions. In some primary schools there is only one teacher. Some don’t have basic facility like class rooms, fans, chair and toilets. Some students have to go more than 5 KM for attending school. A survey named Annual Status of Education Report (ASER), shows that even though the number of rural students attending schools is rising, but more than half of the students in fifth grade are unable to read a second grade text-book and are not able to solve simple mathematical problems. What is the benefit of such education where students are not learning anything? Should not it be government first responsibility to improve basic education and hire more teachers than to start digital education. If there are good schools, digital literacy can be made part of curriculum. But without basic quality education there is no meaning of digital elementary literacy.

Finally comes the IT (information technology). Technology is changing with such a rapid pace that what you learn today will not be useful after 5 years. There was a time when we used floppy disk. Now it’s no more in use. New computers do not even have slot to insert floppy. Now we use CD and DVD or USB. Every years Microsoft launch new version of Windows. Similarly, smart phones are changing rapidly. Ten years back there was no touch screen mobile phones. Apple Inc.  changed everything with touch screen smartphones. If you are not educated and if you do not keep yourself updated, you cannot catchup with technology.

Everyone have dreams, only great Peoples have vision. Without long-term vision India will not become developed nation. A government that makes policies for billionaire businessman and change them according to expected elections result can never take India forward. We need a government with long term Vision.