Should I buy a Split AC or a Window AC?

A room airconditioner is ideal for rooms upto 200 sq.ft when one of the walls is exposed to the outside.

If there are no exposed walls a Split AC is the only option. In addition, in a Split AC the compressor is kept outside and hence, noise levels are lower.

Do I need 3 phase supply if I have to buy an AC for my house?

Window ACs and Mini Split ACs work on single phase. However, it is better to have a 3 phase supply and distribute the other loads like Geysers, washing machines, pumps and lights in the other 2 phases.

How can I reduce heat input into my room?

  • Providing a false ceiling (especially for Room Airconditioners/ Multi-split Airconditioners) reduces the volume to be cooled.
  • Providing curtains/ blinds /sun film on windows reduces heat input into the room.
  • Insulating the ceiling which is exposed to the sun with 50 mm thermocole drastically reduces heat input into the room.

To what distance will a Window AC or Split AC throw air?

A normal Window AC or split AC will throw air upto 15 feet. However, special Split units are available to throw air upto 30 feet.

Do I have to necessarily buy a Voltage Stabilizer when I buy an AC?

The compressor which is the most critical component in the AC works between 190 to 240 V. With voltages in most parts of our Country going well below 190 V, we recommend using a Voltage Stabilizer.

What is the ideal location for a Window AC?

At a height of 5 feet behind you. Ensure that the AC air from the airconditioner does not hit you directly.

How often should I clean my filter?

Filter cleaning depends on the frequency of usage and the atmospheric conditions. For normal applications, it is recommended to clean the filter once in 15 days.

What is Central AC?

For areas more than 500 sq.ft, it is better to cool the air at one point and supply it through ducts to ensure that the distribution of air is uniform at all points. In common parlance this is called "Central AC".

When should I go for Central AC?

  • When your area is more than 500 sq.ft.
  • When you have adequate 3 phase power.
  • When you want to create "plush" interiors.

Should I buy Ducted Splits or Packaged ACs?

Ducted Splits are ideal if floor space is at a premium (or just not available). They are mostly used for areas of 2000 to 3000 sq.ft.

Packaged ACs are more rugged than Ducted Splits and are used where small areas can be spared for locating units. They are more common for areas upto 10000 sq.ft.

Will Split Units spoil my false ceiling?

If units are installed and maintained properly, the false ceiling will be safe. However, if the drain is not sloped properly or the drain pipe is choked, water will overflow into the false ceiling and spoil it. Since the unit is inside the ceiling, the false ceiling has to be opened frequently for attending to the unit. Care must be taken to provide a proper trap door and also handle the trap door properly to ensure that the false ceiling is not spoiled.

How do I know if the AC I am buying is energy efficient?

Ask for the EER (Energy Efficient Ratio) of the AC. The higher the EER, the more energy efficient the AC.

Should I buy Water Cooled units or Air Cooled units?

Water Cooled units are the best choice. They consume less power and have a longer life. However, you will need 15 litres of water per hour per ton of Airconditioning. If this quantity is available then Water Cooled units are the obvious choice. Otherwise, choose Air Cooled units.

Can I use perfumes with my airconditioner?

While perfumes do create a good atmosphere, they should be used cautiously as some people can be allergic to them. The best way to keep the foul smell out is to open windows and use fans to bring in a lot of fresh air before the AC is started. Keeping the AC room clean is also equally important.

Are Central Plants expensive?

No. Central plants with Packaged / Split units cost around 25 K per Ton. With larger customized plants, the prices are higher at around 35 to 40 K per Ton.

Are 3 phase units better than 1 phase units?

3 phase units are better especially when multiple units are used as they ensure better balance on the power system. However, they can be used only if all 3 phases have power, whereas Single phase units can be used even if power is available in any 1 phase.

What kind of AC system should I buy?

While conventional large Central Plants have been used in theatres to take care of the large fresh air load, floor mounted packaged units have become a good option. These units' efficiency in handling fresh air, their multiple steps of control combined with their low cost, have made them the best choice for theatres.

What kind of power bills can I expect?

At Rs. 2.75 per hour (the rates applicable in Tamil Nadu), you can expect a bill of Rs. 1000 per ton per month running 4 shows a day.

Does airconditioning an existing theatre involve a lot of interior changes?

No. Existing theatres can be airconditioned with very little interior changes.

Can I aircondition a part of my theatre?

Yes. By providing a glass partition to the balcony / boxes. Provisions can also be made to aircondition the whole theatre later, if required.

Do I have to necessarily provide a false ceiling if I aircondition my office?

Not necessarily. While false ceiling does reduce the cooling load when non ducted units are used, it is provided mostly for aesthetic purposes. If you have no problems with exposed ducts, you don't have to provide false ceiling. Alternatively, flexible ducts with better finishes and Turbo Splits are also available.

Do I have to necessarily insulate an exposed roof?

We would strongly recommend that you do. Insulating the Underdeck of an exposed roof with 50 mm Thermocole saves nearly 2 Tons of airconditioning. The cooling load with insulation is around 6 Tons. Without the insulation, it would be 8 Tons or 33% more. Not only do you have to pay more initially for larger equipment you will unnecessarily spend money continuously on power.

Some people keep saying it is too cold while others say it is warm - How do I get over this?

The feeling of coolness or warmth is highly individualistic and depends on each person's metabolism. It is however imperative that temperatures are maintained uniformly at each nook and corner of the Office. Balancing the airflow is very important to achieve uniform temperature.

At what temperatures should I set my plant?

Where AC is used for human comfort, the ideal setting is 24oC. AC experts have determined that the comfort zone is between 20 to 25oC with RH between 40% and 60%.

Do I need an operator to operate my AC plant?

Window ACs and Mini Split ACs are very simple to operate and can be operated by individuals in whose cabins these machines are installed.

Ducted Splits and Packaged ACs need a little bit of training and your electrician / office boy can be made to operate these units.

With Central plants it is better to have a trained operator to run the plant continuously.

My room heights are pretty low and my beam bottom is 7'. Are there any ways to aircondition without ducting?

Yes. "Turbo Splits" or Verticools are the right choice.

How much will it cost me to run my AC?

For 10 hrs a day, 25 days a month it will cost you Rs. 1300 at Rs. 3.50/- unit.

Can I keep my front door open when I run my AC?

Keeping the door open obviously means that cold air will get out leading to loss of efficiency in the AC system. However, in establishments where there is no choice but to keep it open "Air Curtains" can be installed. These curtains provide a sheet of air at the opening which prevents cold air from getting out.

I need to ensure that my displays are seen from the road. Hence, I can't provide sun film for glass. How do I take care of my cooling requirements under these conditions?

A good idea would be to provide awnings.

I understand that noise gets carried over in Central AC systems. Will what I say in my room be heard outside?

It is true that improperly designed ducting/ boxing results in sound carry over. However, by designing ducting/ return air collection properly, this can be avoided.

Restaurants/ Bars : I find food smell (or some foul smell) always inside my premises. How should I eliminate this?

Bad smell inside an area prolongs for a long period as the AC system keeps cycling the same air. For areas like Restaurants/Bars, which can handle ACs fresh air like Packaged Units/ Ducted Splits should be used. Keep the fresh air damper in the correct position to ensure flow of fresh air.

I always find a haze of smoke inside my bar? What can I do to eliminate this?

Smoke being heavier than air tends to stay within the airconditioned areas. The absence of fresh air to dilute smoke levels could also result in this. Hence, use Packaged Units/ Splits which can handle fresh air and also ensure higher velocity of supply air in the room to remove the haze.

Hospitals : Can I use Window ACs, Splits for my Operation theatres?

It is important that the patient in an Operation theatre does not get infected. Using Windows/ Splits means recirculating the same air over and over again and it is quite possible that a patient in the theatre picks up an infection from a patient who has had an operation before him.

Hence, depending on the critical nature of operations- Packaged Units or custom designed Central plants should be used.

How do I ensure that I get clean air for my Operation theatres / ICUs?

Bacteria is normally of 1 micron. To ensure that bacteria is filtered, it is necessary to have special filters which can filter upto 0.3 microns. It is also important to circulate the air many times through this filter so that the bacteria gets filtered. Hence, a very high volume of air has to be circulated.

What temperatures are ideal for Operation theatres?

Temperatures of 21 to 22oC are ideal for operation theatres as doctors normally wear heavy clothing and do a lot of physical work during an operation. For other areas, temperatures should be around 24oC.

Software : How much fresh air should I consider for airconditioning a software office?

A Software office is normally heavily populated. Moreover, carpets, printers, xerox machines and other office equipment need a larger quantity of fresh air than normal. It is recommended to use at least 15 cfm of fresh air per person.

How do I keep my operational costs low?

  • Specify energy efficient systems like Scrolls, Centrifugals.
  • Ask for details of part load performance. AC Systems are designed for peak loads which occur only for 2% or so of the time. How the AC works during part loads is important.
  • Use multiple circuits wherever possible for better part load performance.

Should I buy Packaged / Ducted Split units or Central Plants?

Packaged/ Ducted Splits are ideal when

  • Initial cost is a primary concern
  • A large project is done in phases and funds flow will be in phases
  • When different companies/ independent divisions are buying separate wings / floors in a large multistoreyed building.
  • Jobs have to be completed in 2 to 3 weeks.
  • When a full fledged maintenance team is not available at site.
  • Working hours are staggered in different wings/ floors.

Central Plants can be used when

  • A large project has to be completed in one shot.
  • When higher initial costs are acceptable but operating costs have to be lower.
  • Working hours in a large complex are more or less the same.

Blue Star : Manufacturer of Packaged AC, Split AC, Packaged Units and Window ACs in India.

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