Inverter or Non-Inverter Confusion!

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we can't just ignore what is being touted as the USP of this technology and that is that it turns out to be more economical when ACs are run for a long period by running the compressor at a lower capacity which is just enough to maintain the temperature of the room when the excess heat has been dumped out.

Assumes once you take the heat out it magically stays out. How does that happen. If you switch off the unit, how long will it take for the room to heat up again.

Forget how long the unit runs, just think about the heat load and the work required to pump it out.

 

[sultanofswing]

Finally a great, unbiased, discussion on the subject. This thread, more than other brand oriented ones, should help people decide the TYPE of ac based on specs, individual needs and usage patterns.
Brand preferences can come later.
Also, based on these calculations, can the math whiz(zes) come up with a formula (at least a approx one) which takes different variables into account to give a prospective buyer an idea of the total cost involved in owning an ac over a period of 8-10 years?
or maybe it's already mentioned..

 

[rdst_1]

Assumes once you take the heat out it magically stays out. How does that happen. If you switch off the unit, how long will it take for the room to heat up again.

Forget how long the unit runs, just think about the heat load and the work required to pump it out.

It obviously doesn't. And that is what the inverters are supposedly tackling. Instead of cooling and heating cycles they keep running so as to maintain the temp.
Let us say that a room is sized right for a 1.5T AC but after the temp has been reached, assuming the load variation is negligible, the AC only needs to run at 0.6-0.8T so as to maintain that temp . A normal AC will keep cycling between 0 and 1.5T and in my particular case, quite frequently because the difference between desired and ambient temp is mostly above 20°C.
Even for a one room setup this might be saving some money, but when you think of setting up a 2 room setup with a single ODU, that's where an inverter supposedly shines.
For 2 similar rooms, running ACs simultaneously, normal ACs will keep cycling between 0 and 3 T usage whereas you can buy a single 2 T inverter unit and once it has overworked itself cooling the 2 rooms it can easily idle at 1.2-1.5T the whole time and supposedly turn out to be cheaper in the long run, especially for people like my kinda usage where one AC runs for 20hrs and the other for around 16hrs.

This is what I had got when I was researching for a new AC 2 years back. I can obviously be wrong and getting sucked in by BS companies spout to sell a new product. At that moment we went with a normal AC because my Dad wasn't considering changing the AC in their room. That AC is now starting to be troublesome with wire heating issues and the compressor getting switched off for long periods even when the room heats up. Since we will definitely change that unit in a month or two when the temps start getting pretty high. I have paid upto 12k a month as electricity charges last year for the months of June - September despite the unit rates being pretty less than what it is in other parts of India. This is one of the reasons which made me want to look for a more efficient solution.

 

[cranky]

Don't connect dots that aren't meant to be connected.

A temperature differential of 20C is insane and impossible to maintain without severely oversized units, fantastic insulation with minimal entry/exit, extremely low amount of primary energy and a massive electricity bill. For example, a dual-decker hotel freezer with similar differentials (5C in first compartment and -25 in the second) uses ~1MW per month, about 350 for the first unit and 600+ for the second unit. And remember, these are the size of an average bedroom. If you consistently try to achieve that kind of temp drop with a domestic split unit or three over a period of 16 or more hours a day, you're asking for trouble. Going to an inverter unit will not help and you always be in high idle and you will still have compressor wear - worse, in fact, because it will operating continuously for the entire period.

To empty a tank, you can either turn a tap on and off between full and empty, or empty a lot of it at one shot, or open the taps to a trickle, or a combination of the above methods. All that matters eventually is the flowrate of water through the tap and the amount of water in the tank, added to the cost of that tap. Your goals are not compatible with domestic airconditioning offerings. You need to think about your problem in a very different light. Buckets and a tanker are what you need, not a tap.

 

[rdst_1]

Don't connect dots that aren't meant to be connected.

A temperature differential of 20C is insane and impossible to maintain without severely oversized units, fantastic insulation with minimal entry/exit, extremely low amount of primary energy and a massive electricity bill. For example, a dual-decker hotel freezer with similar differentials (5C in first compartment and -25 in the second) uses ~1MW per month, about 350 for the first unit and 600+ for the second unit. And remember, these are the size of an average bedroom. If you consistently try to achieve that kind of temp drop with a domestic split unit or three over a period of 16 or more hours a day, you're asking for trouble. Going to an inverter unit will not help and you always be in high idle and you will still have compressor wear - worse, in fact, because it will operating continuously for the entire period.

To empty a tank, you can either turn a tap on and off between full and empty, or empty a lot of it at one shot, or open the taps to a trickle, or a combination of the above methods. All that matters eventually is the flowrate of water through the tap and the amount of water in the tank, added to the cost of that tap. Your goals are not compatible with domestic airconditioning offerings. You need to think about your problem in a very different light. Buckets and a tanker are what you need, not a tap.

I guess the temperature differential I quoted wasn't right. I meant that I keep the AC on 25 while the outdoor temp is 45-48.
And I get that my usage is definitely on the higher side and that is why I am looking for more efficient solution. Are you saying that I shouldn't be looking at consumer level ACs and perhaps get in touch with some local industrial experts. I have a friend who does interior designing for retail showrooms. I am sure he can get me in touch with his expert friends.

 

[cranky]

25 degrees indoor is a temp difference of about 10 degrees, which is well within domestic range, the unusually high ambient is a challenge, and I am assuming indoor temperature will be about 5 to 10 degrees lower depending on sunlight level etc.

My understanding is that if you need air-conditioning longer than 12 hours a day you need to be looking at an industrial solution. I also assume humidity is on the lower side - correct me if needed - and there are many innovative ways to reduce temperature in dry conditions that do not involve refrigerant and compressors.

 

[rdst_1]

25 degrees indoor is a temp difference of about 10 degrees, which is well within domestic range, the unusually high ambient is a challenge, and I am assuming indoor temperature will be about 5 to 10 degrees lower depending on sunlight level etc.

My understanding is that if you need air-conditioning longer than 12 hours a day you need to be looking at an industrial solution. I also assume humidity is on the lower side - correct me if needed - and there are many innovative ways to reduce temperature in dry conditions that do not involve refrigerant and compressors.

Yup. Humidity isn't much of an issue except for June and July. Till a couple of years ago I used to be happy enough with a water cooler but then became accustomed to an AC and also the water cooler doesn't work in the months of June and July and also the issue of adding water every 5-6 hours which becomes a PITA after a few weeks. I know, what can I say apart from I am lazy.

The rooms become incredibly hot because the roofs and walls have to endure the sun nearly throughout the day due to the bedrooms being at the top floor. Even these days, outside temp being 35/19, I find it uncomfortable to sleep in the bedrooms with just the fans on. Hence I sleep in the drawing room instead which is on the ground floor of the duplex apartment we live in. Also since this is a govt accommodation we can't make any changes to the building.

 

[Rave]

..... and there are many innovative ways to reduce temperature in dry conditions that do not involve refrigerant and compressors.

Do elaborate, Desert coolers and/or desert coolers with ducting?

 

[cranky]

Desert coolers, khus curtains with drip irrigation systems, wet sand under plaster board floor.

 

[rdst_1]

Was browsing online and came across some Daikin Inverter 2.2T for as low as 53-56k on Snapdeal. I am thinking it is an older model because there were some same capacity models from the same company for 70k+ as well.

 

[Niravh]

I had bought a Panasonic 1 ton 2 star (26K free standard installation) some 3 weeks back before i landed on this site/thread. rishigurus posts fascinated the electronics engineer inside of me. i spent approx 10 hours reading this thread. i had to buy another ac for my parents room. i was now sure i am buying an inverter. I realised sales person even in big stores are ignorant of rated capacities of inverters. Like a panasonic ys-series invertor is hardly running at 3..odd versus a sharp 4.02. But then i did my math. 1.1 ton sharp inverter 4.02 without the plasma cluster costs 36500 including standard installation at vijay sales mumbai. thats 10.5 grands costlier than my panasonic 1 ton 2 star. assuming 6 hour per day for 4 months in an year adds to 720 hours p.a. say my panny rated 1.1 kw consumes 720*1.1*6 rs=4752 rs per annum. i can only reasonably assume 50% savings on the inverter thats rs 2376 saved p.a. that puts the breakeven at 4.4 years. thats far too away in the future. i am sure new technologies in cooling will be introduced in next 5 years. so a sharp inverter with high upfront cost seemed unjustified for now. i repeat ordered a new panasonic.
also i have been brainwashed by 'learned' sales guys that the aluminium micro channel condersors while more efficient are likely to get corroded in the mumbai moisture vs copper condensors. i want your views.
also did a small math on non invertor star ratings. want your take on this. a panasonic 1 ton 3 star costs 28.5k.consumes 1.06kw. 40 watts per hour savings amounts to just 28.8 kw savings in the 720 hours. thats some 173 rs p.a. savings over a 2 star. i cudnt justify the 3 star cost.
are my computations correct. your views eddy rishi all.

 

[prakash14]

@Niravh - good to find someone in the same boat as I am I have been trying hard on this forum to mention that inverters or star rated save money only if someone uses it extensively and that too throughout the year. Something like a Bank ATM which needs to run it 24 X 7 for 365 days, then yes you have fast ROI. But if you use it for residence where usage is usually around 100-120 days a year for around 8 hours a day, then the ROI is around 8 years, which many hardly believe. But good that you have done lots of calculations and proved that this entire Star Rated and Inverter is just a marketing gimmick and in day to day usage you will hardly notice any change in your electric bills.

 

[rdst_1]

@Niravh - good to find someone in the same boat as I am I have been trying hard on this forum to mention that inverters or star rated save money only if someone uses it extensively and that too throughout the year. Something like a Bank ATM which needs to run it 24 X 7 for 365 days, then yes you have fast ROI. But if you use it for residence where usage is usually around 100-120 days a year for around 8 hours a day, then the ROI is around 8 years, which many hardly believe. But good that you have done lots of calculations and proved that this entire Star Rated and Inverter is just a marketing gimmick and in day to day usage you will hardly notice any change in your electric bills.

Well I have always been with your school of thought, just never felt like saying anything. 2 years ago I had come to the exact conclusion when researching ACs.
Getting an inverter AC only makes sense if one is running them for around 12-16hrs or more for around 6-8 months. Another advantage of getting an Inverter AC, IMO was that one could undersize as the inverter technology enables the AC to run between 30-120% of the rated capacity. Hence for a room, where one would normally buy a 1.5T AC, a 1T inverter would be enough. In hindsight I should have bought an inverter unit because of our excessive usage. I am gonna post my bills and also I am starting to keep a daily log of my meter readings from today.

 

[Crazy_Eddy]

assuming 6 hour per day for 4 months in an year adds to 720 hours p.a. say my panny rated 1.1 kw consumes 720*1.1*6 rs=4752 rs per annum. i can only reasonably assume 50% savings on the inverter thats rs 2376 saved p.a. that puts the breakeven at 4.4 years. thats far too away in the future.

Yes with lower capacity ACs and lower usage, you will not see the returns as fast as you expect. In fact the savings will be even lower than what you calculated since an AC never runs at 100% duty cycle, and a 50% saving is a high assumption.

But if you use it for residence where usage is usually around 100-120 days a year for around 8 hours a day, then the ROI is around 8 years, which many hardly believe.

One thread you said 2~3 hours, another its 3~4 hours, maybe somewhere else 5~6 hours, now here its 8 hours. When will you decide how many hours you're actually using the AC for? Now do you know why people like me have a hard time understanding your claims?

I had come to the exact conclusion when researching ACs.
Another advantage of getting an Inverter AC, IMO was that one could undersize as the inverter technology enables the AC to run between 30-120% of the rated capacity.

I'm sorry but the 'research' is incorrect . Never ever undersize an Inverter AC since efficiency drops off significantly if the compressor keeps running above rated capacity.
At the same time I'm glad you realised its not possible to use the AC for 2~3 hours, and most people end up using an AC much more than they planned. I have no idea how people sleep comfortably if they wake up in 2 hours to turn off their AC

 

[prakash14]

One thread you said 2~3 hours, another its 3~4 hours, maybe somewhere else 5~6 hours, now here its 8 hours. When will you decide how many hours you're actually using the AC for? Now do you know why people like me have a hard time understanding your claims?

Each statement was made based on that thread conversation. Here I have not mentioned I am using an AC for 8 hours. What I said is if the user uses AC for 8 hours then his ROI would be X amount. Also my claims are realistic figures and based on exact calculations. These are in actual usage scenarios and not under "test conditions" where in someone sets the temperature at 29 and says they save on bills. I consider 25 as a pleasant temperature and all claims are based on the fact that AC X or Y needs to cool it to that level to bring the room temperature down.

At the same time I'm glad you realised its not possible to use the AC for 2~3 hours, and most people end up using an AC much more than they planned. I have no idea how people sleep comfortably if they wake up in 2 hours to turn off their AC

There is something like a timer in almost all ACs so you simply set the AC to shut off automatically after 2 or 3 hours. ACs also have sleep function where in you can automatically increase temperature by a couple of degrees at night so you dont feel the chill

 

[rdst_1]

I'm sorry but the 'research' is incorrect . Never ever undersize an Inverter AC since efficiency drops off significantly if the compressor keeps running above rated capacity.
At the same time I'm glad you realised its not possible to use the AC for 2~3 hours, and most people end up using an AC much more than they planned. I have no idea how people sleep comfortably if they wake up in 2 hours to turn off their AC

I couldn't get my point across properly, I guess. For a 120sq foot room, as in my case, a 1T is considered sufficient, but for efficiency purposes, a 1.5T and above is recommended.
However, because inverter ACs can run at variable speeds/currents, we can actually size the ACs properly and get away with a 1T AC which was actually the correct size in the first place.
This was what I wanted to say.

 

[tornado]

I was planning to upgrade my AC so was reading about Inverter ACs and Inverter regfrigerators. I always wondered what an Inverter AC is and now found that even Inverter fridge exists :O

In this technology the compressor is operated with an inverter. The compressor can very its speed to modulate the cooling output. The inverter converts the incoming AC current into DC current and then it produces current of desired frequency to feed the compressor. The temperature is sensed and accordingly the speed of compressor is adjusted.

In traditional ACs and refrigerators, the compressor is switched off and on to regulate the temperature with the help of thermostat, but it results in less efficiency.

But, Inverter Air conditioners and refrigerators are claimed to save up to 40% more power and run much quiter. They also have more life than traditional ones.

Inverter ACs are much more costly compared to normal ones, is the one time higher cost worth the savings in long run ?

Inverter Refrigerators are also there but currently very expensive in India, are they worth and has anyone got them here?

 

[bigbyte]

also i have been brainwashed by 'learned' sales guys that the aluminum micro channel condensers while more efficient are likely to get corroded in the Mumbai moisture vs copper condensers. i want your views.

It is the other way around actually. Aluminum has better anti corrosive properties than copper. Copper has better heat exchange properties though. In sharp 18MV, the better efficiency with Aluminum is achieved by better micro channel design of condenser.
IIRC, in one of his posts Rishiguru has clarified this as well. In most of the AC's we have copper Aluminum condenser, that leads to corrosion at the junction.