[Aroy]

Originally Posted by Thad E Ginathom

Aroy, that post, subject to my technical limitations, makes sense to me, and is how I thought it worked, as per the second of your quoted statements:

But you seem to be contradicting your earlier post. Or am I confused?

First Statement
The air flow depends on the fan settings of the IDU. The temperature on the speed of compressor in the ODU.

Let me explain
TEMPERATURE
. When compressed gas expands it cools down. When it meets heat it absorbs the heat. How much heat is absorbed in a unit time depends on the thermal characteristics of the gas, the difference in two temperatures and the quantity of gas (flow). That is what ultimately determines the temperature.
. The speed of compressor determines the quantity of gas that will pass through your IDU in a given time (flow).
. So less gas flow means less heat absorbed, in layman's terms less cooling. Conversely more gas flow more cooling.

AIR FLOW
This is set by the blower of the IDU and has nothing to do with the temperature. Just more air flowing through the IDU heat exchanger.

[Thad E Ginathom]

Yes, you put in technical terms how I imagine it to be.

[Prowler]

Other than what Aroy Sir's excellent writeup about the technical side of air conditioning, there is one more variable in play : the sizing of the Aircon with respect to the room size.

If you opt for a bigger unit than needed ( most of us do this as we are in a perennially hot climate zone), the compressor starts cycling on/off at a higher rate. It makes you uncomfortable as it reaches a colder temperature before cutting off.

Second factor is if the IDU fins are clogged, the temperature sensor tends to sense that it has reached the set temperature , cutting the compressor earlier than needed - thus giving the impression that the AC is not cooling enough.

In an ideal world, the temperature sensor should be in the same place where the human occupants are and not living inside the IDU.

[civic-sense]

Originally Posted by anupamsinha

These days almost all installers (in my experience) try and avoid vacuuming. I had to tell them if they want my money they have to go my way.

I am not a forceful person, and it has its downsides.

Originally Posted by Prowler

In an ideal world, the temperature sensor should be in the same place where the human occupants are and not living inside the IDU.

Which is where the remote is located. Modern ACs come with the sensor in the remote. There is a button to toggle between the IDU sensor and remote sensor.

[akshaymahajan]

Scenario: Have a window AC installed in a shaft on the ground floor of a 3 story house. The distance between the AC body and the shaft walls is 1 feet each on all 3 sides.

Does this adversely affect the cooling? My AC technician said so since the hot air thrown out does not have a wind stream, the AC will not be as efficient.

Q1. Is it true? What should be the ideal distance between the back of the AC and the wall?
Q2. Will installing an exhaust fan perpendicularly behind the AC help?
Q3. Can this cause the the coil on the side of the condensor to have ice deposited on it? I always thought that was just due to lack of gas.

Thanks

[Thad E Ginathom]

Originally Posted by civic-sense

Modern ACs come with the sensor in the remote. There is a button to toggle between the IDU sensor and remote sensor.

Gave only vaguely heard of that. What brands are offering this functionality? Sounds like a good one!

[anupmathur]

Originally Posted by akshaymahajan

....
Q1. Is it true? What should be the ideal distance between the back of the AC and the wall?
Q2. Will installing an exhaust fan perpendicularly behind the AC help?
Q3. Can this cause the the coil on the side of the condensor to have ice deposited on it? I always thought that was just due to lack of gas.
....

1) Your AC positioning is certainly not permitting it to perform at optimum values. The hot air discharged from the rear is getting deflected downward (due to the slight slant at which machines are mounted to drain out condensate), and it is largely this hot air that is getting sucked in by the condenser fan intake on the side of the machine.
In such a small shaft there seems to be no solution to this problem.

2) An exhaust fan could help to an extent, but only that - to an extent.

3) Which coil are you talking about, on the side of the condenser? Is it the curved portion of the condenser itself? If yes, I would say it is highly improbable that any ice can ever form on the condenser! If you are seeing a small (few turns) coil near the compressor inlet pipe, then yes, ice could form if there is deficiency of gas in the system.

[sudev]

Originally Posted by akshaymahajan

.......
Q2. Will installing an exhaust fan perpendicularly behind the AC help?
......

Installing a feed fan below the air conditioner level to feed outside air into shaft will be much better.

Hot air from condenser will rise upwards faster and the machine will get cooler air for evaporator.

[Prowler]

Originally Posted by civic-sense

Which is where the remote is located. Modern ACs come with the sensor in the remote. There is a button to toggle between the IDU sensor and remote sensor.

I have 'modern' ACs too. But they don't have this option. May be it comes with the all bells and whistles kind of ACs. Panasonic seems to have a model where some sort of sensor sets the direction of the air flow based on the occupants of the room.

All the ACs I have been saddled with are like Indian weather - all in extremes.

[civic-sense]

Originally Posted by Thad E Ginathom

Gave only vaguely heard of that. What brands are offering this functionality? Sounds like a good one!

Originally Posted by Prowler

I have 'modern' ACs too. But they don't have this option. May be it comes with the all bells and whistles kind of ACs. Panasonic seems to have a model where some sort of sensor sets the direction of the air flow based on the occupants of the room.

All the ACs I have been saddled with are like Indian weather - all in extremes.

During my research, I had come across quite a few models. The Carrier Superia 4i that I bought comes with one, which is by far the cheapest 4 star inverter AC that I have seen.

[akshaymahajan]

Originally Posted by anupmathur

1) Your AC positioning is certainly not permitting it to perform at optimum values. The hot air discharged from the rear is getting deflected downward (due to the slight slant at which machines are mounted to drain out condensate), and it is largely this hot air that is getting sucked in by the condenser fan intake on the side of the machine.
In such a small shaft there seems to be no solution to this problem.

Dammit. The deign of that room doesnt allow for any other placement of the air conditioner. I may need to check out these Portable ACs I see online.

2) An exhaust fan could help to an extent, but only that - to an extent.

Noted

3) Which coil are you talking about, on the side of the condenser? Is it the curved portion of the condenser itself? If yes, I would say it is highly improbable that any ice can ever form on the condenser! If you are seeing a small (few turns) coil near the compressor inlet pipe, then yes, ice could form if there is deficiency of gas in the system.

Sorry, I meant the small copper coil/turns on the side of the front portion of the AC, behind the filter and with those delicate fins (Evaporater Coil??)

Originally Posted by sudev

Installing a feed fan below the air conditioner level to feed outside air into shaft will be much better.

There isnt an inlet for outside air since this shaft is in the middle of the house. But I see your point.

[anupmathur]

Originally Posted by akshaymahajan

.... I may need to check out these Portable ACs I see online.
....

The portable ACs are usually very poor compared to a standard window unit. Moreover, the portable AC's ODU will suffer from the same problems as the window AC, assuming you'd put the ODU in the small pipe-shaft.

[Aroy]

Originally Posted by akshaymahajan

Scenario: Have a window AC installed in a shaft on the ground floor of a 3 story house. The distance between the AC body and the shaft walls is 1 feet each on all 3 sides.

Does this adversely affect the cooling? My AC technician said so since the hot air thrown out does not have a wind stream, the AC will not be as efficient.

Q1. Is it true? What should be the ideal distance between the back of the AC and the wall?
Q2. Will installing an exhaust fan perpendicularly behind the AC help?
Q3. Can this cause the the coil on the side of the condensor to have ice deposited on it? I always thought that was just due to lack of gas.

Thanks

More than the distance of walls it is the air circulation that matters. Your AC's are in a deep well where natural ventilation is scarce. An exhaust fan blowing the air up will help a lot. The only problem is that the fan has to be rain proof and sturdy enough to weather 50+ temperature that will develop in this enclosed space during hot summers.

To increase cooling of the hot side, you can put a tank on the AC that will slowly drip water on to the hot coils. This used to be a standard procedure in the days when Voltas and Carrier were practically the only AC used in Delhi.

[anupmathur]

Originally Posted by Aroy

....
To increase cooling of the hot side, you can put a tank on the AC that will slowly drip water on to the hot coils. This used to be a standard procedure in the days when Voltas and Carrier were practically the only AC used in Delhi.

This was indeed common practice in days of yore but would it be advisable with today's 'high-tech' condensers made of thin-wall tubes and fins? Most places have 'hard water' which leaves scale on evaporation. These modern day condensers cannot take chemical de-scaling/cleaning without suffering damage.

[Aroy]

Originally Posted by anupmathur

This was indeed common practice in days of yore but would it be advisable with today's 'high-tech' condensers made of thin-wall tubes and fins? Most places have 'hard water' which leaves scale on evaporation. These modern day condensers cannot take chemical de-scaling/cleaning without suffering damage.

The idea is to wet the fins so that thermal transfer is enhanced.

As the older tank used to hold 5 liters or so, you can always use RO water. Modern RO systems provide decent descaling, so there should be no fear of spoiling the fins.