For a change, and to start back with my blog, I have chosen a different topic from the intended contents of this blog.
It is known universally that CAG report is tabled officially in the parliament also, but the parliament can not function. The ruling party and all opposition parties together (for the first, and may be last, time)are fighting as to how to fight further! They seem to be not interested in finding an answer to anthing, but just keep fighting for the sake of fighting!
It is JPC vs PAC or, now a discussion, as per the PM. I have a basic doubt, that is only technical, though in my opinion it is more relavent than than all these English letters!
What is a CAG, besides the fact that it is a three letter short form for Comtroller and Auditor General (Of India, not US)? What does the C stand for, or what does the CAG control?
In fact this agency seems to fucntioning better than CBI or CVC (all three lettered ones)! Why not empower this agency with more power to control, than just simply produce reports that have no power to it? Or atleast make him a two lettered fellow as AG and cut the C from him!
Then we can see how else the parties decide further to fight and enjoy their days in the pariament!
Monday, November 22, 2010
Saturday, December 05, 2009
One more fire in Chennai
A few days back one more fire was reported: This time from a bank in Tambaram, Chennai. Though it was not reported to be a fire from AC, we got communication/confirmation to that effect.
Why it happened? Can it be avoided?
Though there could be many reasons for the fire in an equipemnt, one reason that I can point out is; The termination of incoming electrical power supply to the indoor units of the split AC, rather than at the outdoor. When it is done this way, there is always a possibility of fire at the terminals whever the compressor starts or stops drwaing high current. The easieat way to eliminate atleast this one possibility is to insist on termination power at the outdoor.
Unfortunately many manufactureres do not have provosion for this: And the simple and SILLY reason? Cost control! By saving a few meters of wiring by whoever is doing that: In most cases the clinet will have to get it done, and to make him happy, manufacturers resort to this dangerous practice.
Can we expect some responsible behaviour from them?
Why it happened? Can it be avoided?
Though there could be many reasons for the fire in an equipemnt, one reason that I can point out is; The termination of incoming electrical power supply to the indoor units of the split AC, rather than at the outdoor. When it is done this way, there is always a possibility of fire at the terminals whever the compressor starts or stops drwaing high current. The easieat way to eliminate atleast this one possibility is to insist on termination power at the outdoor.
Unfortunately many manufactureres do not have provosion for this: And the simple and SILLY reason? Cost control! By saving a few meters of wiring by whoever is doing that: In most cases the clinet will have to get it done, and to make him happy, manufacturers resort to this dangerous practice.
Can we expect some responsible behaviour from them?
Friday, June 05, 2009
Unfortunate fire in a running AC indoor unit
Many of you might be aware of a fire accident in Chennai a few days back, where a few months old baby died, while sleeping in the bed! My condolences to the family for the irreplacable loss of a precious life.
In most of the AC units that are available in the market, it is the usual practice to terminate the incoming power in the indoor unit, that is very convenient for the installing contractor. And for the brand it results in an overall cost reduction, offfering an edge in price!
However it is the compressor that draws the maximum current in an AC unit. And it is located in the outdoor unit. This power is routed through either a contactor or a relay. Due to frequent starting and stopping of the compressor in an unit by the thermostat, there are possibilities of the contact getting damaged and sparks appearing. This remais a potential fire hazard always. Why is this contact located in the indoor unit then?
If the contcat is shifted to the outdoor unit this problem is atleast shifted to the outdoor unit and is away from the bed! Will the manufacturers and the government atleast wake up now?
In most of the AC units that are available in the market, it is the usual practice to terminate the incoming power in the indoor unit, that is very convenient for the installing contractor. And for the brand it results in an overall cost reduction, offfering an edge in price!
However it is the compressor that draws the maximum current in an AC unit. And it is located in the outdoor unit. This power is routed through either a contactor or a relay. Due to frequent starting and stopping of the compressor in an unit by the thermostat, there are possibilities of the contact getting damaged and sparks appearing. This remais a potential fire hazard always. Why is this contact located in the indoor unit then?
If the contcat is shifted to the outdoor unit this problem is atleast shifted to the outdoor unit and is away from the bed! Will the manufacturers and the government atleast wake up now?
Thursday, January 04, 2007
Cool, when you don’t need it! (?) Part I
In our earlier article on
‘How to use AC equipments efficiently’
we concluded by stating that, how to put into beneficial use energy saved by shifting the residences as well as small offices from conventional AC units to inverter based units.
Once upon a time offices used to work from 9 to 5!
No more now: Most of the IT companies work at nights: All call centers work more during nights: Even factories working round the clocks require air conditioning for a lot of areas.
Thus in addition to residences and a very few areas that required air conditioning at nights, a lot more air conditioning is called for at nights. In one way it is good. Because when energy is produced to meet the peak load during the day time, the reduced loads at nights was posing a problem of balancing the production with reduced demand. I believe, it is not an easy task. Well, I will limit myself with this fact, as I am not an expert in it.
Thus there is a need to create loads at nights also, so that production continues without any hitch. That is to say, create work for the sake of consuming available energy!
Air conditioning gives an ideal answer here. In addition, if a new air conditioning technology is available that can take advantage of the reduced demands due to the shift described above any time of the day, it is also beneficial.
Like energy has to be consumed when there is no actual demand,
We need a process of air conditioning that produces cooling, when there is no demand!
Surprising? But a way has been found. We will touch on it in our next posting.
‘How to use AC equipments efficiently’
we concluded by stating that, how to put into beneficial use energy saved by shifting the residences as well as small offices from conventional AC units to inverter based units.
Once upon a time offices used to work from 9 to 5!
No more now: Most of the IT companies work at nights: All call centers work more during nights: Even factories working round the clocks require air conditioning for a lot of areas.
Thus in addition to residences and a very few areas that required air conditioning at nights, a lot more air conditioning is called for at nights. In one way it is good. Because when energy is produced to meet the peak load during the day time, the reduced loads at nights was posing a problem of balancing the production with reduced demand. I believe, it is not an easy task. Well, I will limit myself with this fact, as I am not an expert in it.
Thus there is a need to create loads at nights also, so that production continues without any hitch. That is to say, create work for the sake of consuming available energy!
Air conditioning gives an ideal answer here. In addition, if a new air conditioning technology is available that can take advantage of the reduced demands due to the shift described above any time of the day, it is also beneficial.
Like energy has to be consumed when there is no actual demand,
We need a process of air conditioning that produces cooling, when there is no demand!
Surprising? But a way has been found. We will touch on it in our next posting.
Saturday, December 30, 2006
Sizing an air conditioner for Indian conditions
(Contuation of earlier article will appear after this post!)
Sizing an air conditioner
Recently I read in an Indian HVAC magazine the following.
0.5 TR AC for upto 250 sft(25 SQM),
1 TR Ac for upto 550 sft(55 sqm), and
2 TR for upto 1400 sft (140 sqm).
Is it not very surprising? For, this one seems to be addressing residences!
Even in a multistoried complex, with all the floors conditioned, these figures are going to be impossible to achieve.
I feel the data would be correct if it reads like:
With Indian ambient conditions, 0.5 TR is ruled out for many applications. Hence,
1 TR for up to 120-200sft,
1.5 TR for up to 150-250 sft &
2 TR for upto 200-300 sft!
depending upon other factors.
Sizing an air conditioner
Recently I read in an Indian HVAC magazine the following.
0.5 TR AC for upto 250 sft(25 SQM),
1 TR Ac for upto 550 sft(55 sqm), and
2 TR for upto 1400 sft (140 sqm).
Is it not very surprising? For, this one seems to be addressing residences!
Even in a multistoried complex, with all the floors conditioned, these figures are going to be impossible to achieve.
I feel the data would be correct if it reads like:
With Indian ambient conditions, 0.5 TR is ruled out for many applications. Hence,
1 TR for up to 120-200sft,
1.5 TR for up to 150-250 sft &
2 TR for upto 200-300 sft!
depending upon other factors.
How to run AC units efficiently at home or office? PART 6
Now you have selected and installed a inverter unit. Setting up the required temperature is your job, as you only must know what you want!
After this is over, let us assume that you have just entered the room and switched on the unit. As the room was unconditioned till then, the difference between the set point and room temp at that time will be high. Sensing this, the system sets itself to produce maximum cooling. The temp starts approaching the set point. As soon as the room temperature is reached, the compressor does not cut off now. Some heat continues to flow into the room constantly, the compressor runs at a matching speed just producing that much of cooling only. So there is no questioning of over cooling. We have eliminated the requirement for thermostat having to perform two opposing functions at a single set point. It simply keeps relaying the room temperature only to the control system. Now that the need for more or faster cooling is over, the compressor receives a command to reduce its speed. Thus the room temperature just stays where you want it to stay with no fluctuations or cycling. As there is no frequent staring and stopping of compressor, the power supply also does not get disturbed. Thus the unit meets the cooling demand as per needs, producing more at the beginning till the room is fully cooled, and then adjusting its speed in line with the room load.
Imagine this type of units being used by all. Will it not be nice? The energy demand will be reduced especially in nights, and voltage as a result will stay more stable! Government can relax, having solved the problem of shortage of electricity as well as avoiding fluctuations in voltages!
Thus having reduced the momentary demand to lower values from users of such small capacity clients, how can this benefit be passed on to the industry or commercial sector?
We will see it in our next topic.
After this is over, let us assume that you have just entered the room and switched on the unit. As the room was unconditioned till then, the difference between the set point and room temp at that time will be high. Sensing this, the system sets itself to produce maximum cooling. The temp starts approaching the set point. As soon as the room temperature is reached, the compressor does not cut off now. Some heat continues to flow into the room constantly, the compressor runs at a matching speed just producing that much of cooling only. So there is no questioning of over cooling. We have eliminated the requirement for thermostat having to perform two opposing functions at a single set point. It simply keeps relaying the room temperature only to the control system. Now that the need for more or faster cooling is over, the compressor receives a command to reduce its speed. Thus the room temperature just stays where you want it to stay with no fluctuations or cycling. As there is no frequent staring and stopping of compressor, the power supply also does not get disturbed. Thus the unit meets the cooling demand as per needs, producing more at the beginning till the room is fully cooled, and then adjusting its speed in line with the room load.
Imagine this type of units being used by all. Will it not be nice? The energy demand will be reduced especially in nights, and voltage as a result will stay more stable! Government can relax, having solved the problem of shortage of electricity as well as avoiding fluctuations in voltages!
Thus having reduced the momentary demand to lower values from users of such small capacity clients, how can this benefit be passed on to the industry or commercial sector?
We will see it in our next topic.
How to run AC units efficiently at home or office? PART 5
These new units are called DC INVERTER AC units, with rotary or scroll compressors. We are limiting our attention to rotary compressors that is considered better for the lower capacities.
The very basic difference, from your point of view is that, these systems produce exactly the amount of cooling required by a room, and not a fixed cooling having no relevance to the room load like the earlier units discussed above.
It is enough for you to know this much.
They achieve this by running the compressor at varying speeds, and not at a fixed speed. Since DC motors can be better controlled, they employ a DC motor instead of AC motors that is adopted in earlier AC units.
How does it satisfy YOU?
Wait for the next part.
The very basic difference, from your point of view is that, these systems produce exactly the amount of cooling required by a room, and not a fixed cooling having no relevance to the room load like the earlier units discussed above.
It is enough for you to know this much.
They achieve this by running the compressor at varying speeds, and not at a fixed speed. Since DC motors can be better controlled, they employ a DC motor instead of AC motors that is adopted in earlier AC units.
How does it satisfy YOU?
Wait for the next part.
How to run AC units efficiently at home or office? PART 4
(For the time being we are ignoring the existence of Inverter type units)
The heat loads are normally estimated for the worst ambient conditions and units are selected. However the actual load seldom remains the same because the ambient temperature keeps varying. However once a unit is selected and installed, it always tries to produce its full capacity possible at that ambient condition, irrespective of the actual cooling required. Though there is a thermostat, the room goes through a cyclic cooling, which makes the occupant feel uncomfortable. The cyclic process is unavoidable for a few reasons. First, the rate at which cooling is produced is never equal to the rate which heat enters the room. Hence the unbalance always produces un-comfortableness. Second, the thermostat being a mechanical device requires two end points to cut off the compressor and restart it a little latter. When the cutting off takes place, say at 24 ˚ C, then the next minute theoretically it would have to restart because the temperature would have risen. But in practice it is allowed to do so, as otherwise the compressor starts cycling, or repeatedly starts and stops. This not only disturbs the power supply systems characteristics, but also the life of the compressor itself! Also practically it is impossible to produce a device that does two opposing functions at a single point, namely cutting off and restarting. Hence a gap is given in the device to function, which is referred to as ‘differential’. Either it is allowed to overcool and restart at the set point or cuts off at the set point but restarts at a slightly higher temperature!
In addition the human body is so sensitive to temperature, that at the same indoor temperature, it feels differently during summer and winter. (i.e) You may feel very comfortable at 22 ˚ C during summer, but during winter a slightly higher temperature will feel more comfortable. The poor combination of your compressor and thermostat do not understand this.
So as long as you have installed an equipments that produces constant cooling irrespective of the load, you have to set your preferred temperature in the thermostat and accept a cyclic nature of indoor temperature and be comfortable with that!
Now enter the new variety of, not only ENERGY EFFICIENT AC units, but also units that can think like you!
The heat loads are normally estimated for the worst ambient conditions and units are selected. However the actual load seldom remains the same because the ambient temperature keeps varying. However once a unit is selected and installed, it always tries to produce its full capacity possible at that ambient condition, irrespective of the actual cooling required. Though there is a thermostat, the room goes through a cyclic cooling, which makes the occupant feel uncomfortable. The cyclic process is unavoidable for a few reasons. First, the rate at which cooling is produced is never equal to the rate which heat enters the room. Hence the unbalance always produces un-comfortableness. Second, the thermostat being a mechanical device requires two end points to cut off the compressor and restart it a little latter. When the cutting off takes place, say at 24 ˚ C, then the next minute theoretically it would have to restart because the temperature would have risen. But in practice it is allowed to do so, as otherwise the compressor starts cycling, or repeatedly starts and stops. This not only disturbs the power supply systems characteristics, but also the life of the compressor itself! Also practically it is impossible to produce a device that does two opposing functions at a single point, namely cutting off and restarting. Hence a gap is given in the device to function, which is referred to as ‘differential’. Either it is allowed to overcool and restart at the set point or cuts off at the set point but restarts at a slightly higher temperature!
In addition the human body is so sensitive to temperature, that at the same indoor temperature, it feels differently during summer and winter. (i.e) You may feel very comfortable at 22 ˚ C during summer, but during winter a slightly higher temperature will feel more comfortable. The poor combination of your compressor and thermostat do not understand this.
So as long as you have installed an equipments that produces constant cooling irrespective of the load, you have to set your preferred temperature in the thermostat and accept a cyclic nature of indoor temperature and be comfortable with that!
Now enter the new variety of, not only ENERGY EFFICIENT AC units, but also units that can think like you!
How to run AC units efficiently at home or office? PART 3
First you must understand the approximate temperature you feel comfortable at. Then set the temperature to a value equal to or slightly higher than that. Otherwise you suffer like as described above. If you do not know your preferred temperature, find it out. It is simple, but requires a little patience and time. First set the thermostat, say at about 24 ˚ C if there is any marking on the thermostat, or set the pointer of the thermostat to roughly point to 1 ‘O clock position of your clock! Run the unit for a reasonable time, say one day at least. If you feel you require more cooling, then set it at say 23 ˚ C or point it to 2 ‘O clock position (Rotate it to your right). If you feel too cold, then do the opposite. Set it close to 12 ‘O clock position or at 25 ˚ C. After doing such adjustment, again allow the unit to run at least for a day. Then if you still feel not satisfied, repeat the above steps in the direction desired by you. Till you finally feel satisfied.
Now as soon as your temperature is reached in the room, no more cooling is delivered to you as the thermostat would have ordered the compressor to shut off, so you feel comfortable. As soon as the temperature rises above your preferred temperature the compressor again starts because of the command from the thermostat and the process is repeated.
Now there are a few problems with these units. What are they? We will see it in next part.
Now as soon as your temperature is reached in the room, no more cooling is delivered to you as the thermostat would have ordered the compressor to shut off, so you feel comfortable. As soon as the temperature rises above your preferred temperature the compressor again starts because of the command from the thermostat and the process is repeated.
Now there are a few problems with these units. What are they? We will see it in next part.
How to run AC units efficiently at home or office? PART 2
All the AC units are equipped with either reciprocating/rotary/scroll compressors with a thermostat and another button that said, “Off/Fan/Low cool/medium cool/high cool” or similar.
The common misconception amongst many people was that you set the temperature to say, 18˚ C or so, you get good cooling!
It is not so. The rate at which cooling produced has got no relation to the set point temperature of the thermostat.
Unfortunately your AC does not know what you are thinking! The thermostat does its job perfectly and the compressor does its job even more perfectly. How?
Thermostat will keep sensing only the room temperature. If the room temperature is higher than the temperature that you have set, it will simply tell the compressor to keep running. As soon as the set temperature is sensed, with a little bit of safety margin, it will ask the compressor to shut off.
As far as the compressor is concerned, it does not understand the concept of temperature or set point. As long as it gets instruction from the thermostat, ordering it to run, it will keep running. Even if the occupant is freezing to death! That is why many times you would have been compelled to get up and shut off or adjust the unit in the middle of the night. Or if you had a remote, you would have only saved yourself the trouble of getting up. Nothing more than that!
Is there not a better way address the problem? There is. We will see it part 3.
The common misconception amongst many people was that you set the temperature to say, 18˚ C or so, you get good cooling!
It is not so. The rate at which cooling produced has got no relation to the set point temperature of the thermostat.
Unfortunately your AC does not know what you are thinking! The thermostat does its job perfectly and the compressor does its job even more perfectly. How?
Thermostat will keep sensing only the room temperature. If the room temperature is higher than the temperature that you have set, it will simply tell the compressor to keep running. As soon as the set temperature is sensed, with a little bit of safety margin, it will ask the compressor to shut off.
As far as the compressor is concerned, it does not understand the concept of temperature or set point. As long as it gets instruction from the thermostat, ordering it to run, it will keep running. Even if the occupant is freezing to death! That is why many times you would have been compelled to get up and shut off or adjust the unit in the middle of the night. Or if you had a remote, you would have only saved yourself the trouble of getting up. Nothing more than that!
Is there not a better way address the problem? There is. We will see it part 3.
Friday, September 29, 2006
How to run AC units efficiently at home or office? PART 1
How to save electricity?
How to keep your current bill under YOUR control?
How do you set your thermostat to be comfortable yet spent less on electricity?
How to make your AC think like you?
These are common questions faced by all.
But a very few take the trouble of understanding it.
===================================================================================
In India atleast, it is not very uncommon to see a client buying the best TV at a higher price, but buying an AC that is cheaper! By watching that TV he does not spend much elctricity additionally: But he is going to spend more on elctricity by running the AC. Hence it makes a lot of sense to buy an efficient AC. Still he chooses to buy a cheaper unit! It is ironical. Is it not? I am not attempting to change one's buying preferences, which I can't. I can only tell how you can run any AC atleast effectively! '
=================================================================================== contd....... in Part 2
How to keep your current bill under YOUR control?
How do you set your thermostat to be comfortable yet spent less on electricity?
How to make your AC think like you?
These are common questions faced by all.
But a very few take the trouble of understanding it.
===================================================================================
In India atleast, it is not very uncommon to see a client buying the best TV at a higher price, but buying an AC that is cheaper! By watching that TV he does not spend much elctricity additionally: But he is going to spend more on elctricity by running the AC. Hence it makes a lot of sense to buy an efficient AC. Still he chooses to buy a cheaper unit! It is ironical. Is it not? I am not attempting to change one's buying preferences, which I can't. I can only tell how you can run any AC atleast effectively! '
=================================================================================== contd....... in Part 2
Friday, December 09, 2005
What temperature for Chennai?
Chennai or Madras has got a high ambient temperature. The seasons that we are blessed with are known commonly as HOT, HOTTER, & HOTTEST!
While no one can deny the fact that AIR CONDITIONING is almost a must for any organisation, what should be the inside design temperature for a hotter place like Chennai?
In most of the IT companies it is found that temperatures close to 72 deg F(22.2 deg C) are selected or recommended for the general workstation areas.
Do we really need that? In western countries, where there is more need to heat, there is meaning in limiting the temperatures to lower and acceptable limits. But do we need to copy that when our requirement is just the opposite of heating, or having to cool most of the times? Does it not make sense to keep the temperatures a litle higher but at an acceptable level?
On one side everyone talks of the need to conserve energy, but on the other side we compel equipements to consume more energy by pushing the set point to lower levels.
Who is responsible for this? The clients or the consultants?
On the other hand the requird importance is not fully given to fresh air needs(by the designer initially and/or by the client latter).
Systems are simply overdesigned, with less importance to fresh air.
May be two negatives make one positive!
While no one can deny the fact that AIR CONDITIONING is almost a must for any organisation, what should be the inside design temperature for a hotter place like Chennai?
In most of the IT companies it is found that temperatures close to 72 deg F(22.2 deg C) are selected or recommended for the general workstation areas.
Do we really need that? In western countries, where there is more need to heat, there is meaning in limiting the temperatures to lower and acceptable limits. But do we need to copy that when our requirement is just the opposite of heating, or having to cool most of the times? Does it not make sense to keep the temperatures a litle higher but at an acceptable level?
On one side everyone talks of the need to conserve energy, but on the other side we compel equipements to consume more energy by pushing the set point to lower levels.
Who is responsible for this? The clients or the consultants?
On the other hand the requird importance is not fully given to fresh air needs(by the designer initially and/or by the client latter).
Systems are simply overdesigned, with less importance to fresh air.
May be two negatives make one positive!
Friday, December 02, 2005
AIR COOLED vs WATER COOLED
It is generally accepted that water cooled chillers consume less energy than air cooled units for the same capacity. But is that all, that need to be considered while selecting a system?
Air is (still) free, it is not charged! But water? Even if one is willing to pay for it, can the required quantity be continuously assured? That too in summer, when air conditioning is essentially required? Water of the same quality through out the year? Are clients willing to invest on water treatment plants? Can they be easily maintained or, will they ever be maintained at all? What happens if the parameters are not maintained? Does any one, really understand the effect of fouling factor etc in the long run, as a result of the above factors?
I WISH OUR COMMUNITY CONSIDERS ALL THESE WHILE RECOMMENDING AGAINST OR A FOR ANY SYSTEM!
Air is (still) free, it is not charged! But water? Even if one is willing to pay for it, can the required quantity be continuously assured? That too in summer, when air conditioning is essentially required? Water of the same quality through out the year? Are clients willing to invest on water treatment plants? Can they be easily maintained or, will they ever be maintained at all? What happens if the parameters are not maintained? Does any one, really understand the effect of fouling factor etc in the long run, as a result of the above factors?
I WISH OUR COMMUNITY CONSIDERS ALL THESE WHILE RECOMMENDING AGAINST OR A FOR ANY SYSTEM!
Invitation
This site is intended to be used for the benefit of all AIR CONDITIONING professionals in and around Chennai.
Anything on the subject, that will be useful for those who are new to the profession are welcome.
To start with, I define air conditioning in simple language as,
" A process of altering the temperature, humidity and cleanliness of air for use at controlled velocities for HUMAN comfort or to aid industrial processess"
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