[Prowler]

Originally Posted by Thad E Ginathom

My 2.2 tonner... Well, I should have saved 17k and got the 1.9. This one is actually too powerful! It is a Monster AC!

I am afraid your Monster AC will never get to see full load even in the peak of summer. You can cool adjacent area if you want to.

A long time ago, an Air conditioning engineer friend of mine told me that once in a while, you have to run the AC at full blast for an hour or so to keep them in 'shape'. I don't know if that rule is still valid for inverter ACs.

Using an over sized AC unit will not allow the humidity level to drop as the compressor keeps turning off (in a conventional unit).

[Thad E Ginathom]

Originally Posted by Prowler

Using an over sized AC unit will not allow the humidity level to drop as the compressor keeps turning off (in a conventional unit).

And, with an inverter, I don't think that the compressor is ever entirely off? So, even if one sets the temperature to higher-than-ambient, some cooling happens. On the other hand, the humidity stays nice and even!

Actually, I have it set to 27 at this moment, and the temperature at my desk, 30 feet away actually is 27, and humidity is comfortable: that would not have happened with the old, departed (nearly. It still has some life left in it) machine.

[sandeepmohan]

Originally Posted by Prowler

I don't know if that rule is still valid for inverter ACs.

Not required at all for any kind of aircon. Helps flooring your car once in a while though

What should be done is run the aircon as you normally would even during non summer times. Power it up once in a while if you see a situation of the unit not being used for months. This is to keep refrigerant oil flowing inside the compressor crankshaft area.

Weather patterns have changed. What used to be running the aircon for 3 months in a year is now almost 6-8 months depending on where you live. If you live in a coastal town, there is no question of not running your aircon.

[anupmathur]

Originally Posted by Prowler

....
Using an over sized AC unit will not allow the humidity level to drop as the compressor keeps turning off (in a conventional unit).

Not so! An oversized AC cuts off because it has brought the temperature to the set value. And, condensing the moisture out from the air depends on the temperature alone and not the duration the compressor is on for.

[Prowler]

Originally Posted by sandeepmohan

Not required at all for any kind of aircon. Helps flooring your car once in a while though

What should be done is run the aircon as you normally would even during non summer times. Power it up once in a while if you see a situation of the unit not being used for months. This is to keep refrigerant oil flowing inside the compressor crankshaft area.

Thanks. But I vaguely remember him telling me something about some pressure being high when you set the temp low and hence the need to set the thermostat at the low value.

Originally Posted by anupmathur

Not so! An oversized AC cuts off because it has brought the temperature to the set value. And, condensing the moisture out from the air depends on the temperature alone and not the duration the compressor is on for.

.
I will quote from a reputed source the relevant details:

When sizing air conditioners, be careful not to make the mistake of getting one that is too large. If the system you install is too large for the space, it will short cycle. In other words, the compressor will not run long enough to dehumidify the space and will limit your comfort. In addition, it will cycle on and off more frequently, increasing operating costs and reducing the system life. Proper air conditioner sizing is critical to optimize performance.

[anupmathur]

Originally Posted by Prowler

....
I will quote from a reputed source the relevant details:

I would disagree still. Please cite the source so I can better understand exactly what they mean. As a general rule, an oversized AC will not create any problem with de-humidification.

[Thad E Ginathom]

An over-size AC might cycle too often (hmm... for what value of "too often?") but I'd guess that an inverter machine will simply run at lower capacity anyway.

[Aroy]

When the AC is on the outlet temperature is quite low - 5 to 12 degrees. When it is off the temperature is around the room temperature.

For dehumidifying, lower temperature helps as lower the temperature lower is the dew point (at which air just condenses the water vapour).

So to come back, the longer the AC runs the faster is dehumidification. An oversized AC which switches off more will thus dehumidify at a slower rate than an AC which runs longer.

[anupmathur]

Originally Posted by Aroy

....
So to come back, the longer the AC runs the faster is dehumidification. An oversized AC which switches off more will thus dehumidify at a slower rate than an AC which runs longer.

You seem to be overlooking the fact that to condense the moisture from air also needs cooling effect (wasted cooling); which means that a large AC will not cut-off till the dehumidification is nearly complete (assuming no introduction of more moisture rich ambient air from outside).
In fact, the first effect on starting the AC is copious amounts of condensate formation. It is only after this that the actual room cooling truly begins.
Do try it and see for yourself that the result is not as intuitive as it may seem.
Slower fan speed on a large AC will totally resolve this issue, if it exists at all in a given situation.

[Prowler]

Originally Posted by anupmathur

I would disagree still. Please cite the source so I can better understand exactly what they mean. As a general rule, an oversized AC will not create any problem with de-humidification.

Specifically this: https://www.acdirect.com/ac-package-...ing-calculator

There are others with similar information - all suggesting that an over sized AC will have a negative effect on humidity. Another quote :

If you buy an air conditioner that is too small, the unit will be overworked trying to pump out more cool air than is possible and will eventually fail. On the other hand, an air conditioner that is too large will cool off the room too quickly and the humidity will hang in the air, leaving you clammy and chilly. Consider the number of human occupants likely to occupy in that room and other factors like insulation of the roof, the number of windows and the machinery installed in that room before you arrive at the tonnage of the air-conditioner.

I am not here to argue. I just wanted to show what the general scientific perception about the sizing of an AC is.

[reignofchaos]

Need two air-conditioners for the guest room and my home office. The guest room one could be a cheap 1T unit with low efficiency which will be used only once in a while. The other one should be a high efficiency 1T unit. Any suggestions? I've had good luck with panasonic units so far.

[Thad E Ginathom]

I wanted Panasonic for ages! I don't really know how it got dropped from my list. If it has been good for you, maybe you should stick with it.

[aim120]

Originally Posted by reignofchaos

Need two air-conditioners for the guest room and my home office. The guest room one could be a cheap 1T unit with low efficiency which will be used only once in a while. The other one should be a high efficiency 1T unit. Any suggestions? I've had good luck with panasonic units so far.

High efficiency 5 star you can go for Daikin JTKM or JTKJ35 it uses R32 gas which was invented by Daikin but is royalty free.



Godrej also has NXJ 5 star models, it uses R290 gas aka propane, which is even more green but highly flammable.(so a trained installer is a must)

R410A will also be phased out in the coming years.

[aim120]

Originally Posted by anupmathur

Not so! An oversized AC cuts off because it has brought the temperature to the set value. And, condensing the moisture out from the air depends on the temperature alone and not the duration the compressor is on for.

Originally Posted by Thad E Ginathom

An over-size AC might cycle too often (hmm... for what value of "too often?") but I'd guess that an inverter machine will simply run at lower capacity anyway.

Condensing moisture depends on temperature and humidity. Check the dew point chart.


My room is 190sq feet and we have a 1.5ton 5 star ISEER 5.20 Daikin inverter AC, it runs at full load max for an hour in summer, typically about 30min.

Early in the morning like 2AM to 6AM, it reduces the compress load to just 8 to 12%, during this time when one checks the temperature it has achieved the set temperature of 23c but it is not removing the humidity enough. So one starts to feel discomfort (atleast people who are further away or non line of sight with respect to airflow and swing disabled) and as minutes or hours go by the room even smells stuffy (if its at 8%). In order to remedy this the compressor has to run at 20% capacity or more, so the only way to achieve that is by opening the door for a few minutes (In my case I have a exhaust fan with shutter and timer, although I will have to search for a silent exhaust fan) or reduced the set temperature even further (this however is very cold for people closer to the AC or in the path of the airflow).

So I feel the AC is overpowered since the peak cooling capacity of 6kw is equal to a 1.8ton split or 2 ton window AC mentioned in the AC brochure 3 year ago. So may be I should have bought a 1 ton AC.

[reignofchaos]

Originally Posted by aim120

High efficiency 5 star you can go for Daikin JTKM or JTKJ35 it uses R32 gas which was invented by Daikin but is royalty free.

Godrej also has NXJ 5 star models, it uses R290 gas aka propane, which is even more green but highly flammable.(so a trained installer is a must)

R410A will also be phased out in the coming years.

Shall check the Daikins. I'd rather stay away from Godrej altogether after the horrible experience my parents had with a godrej fridge.

Any options for the low end one? Ideally would want that to be around 20-25k.