Air Conditioning means heating the premises in the winter and cooling it in summer by keeping the temperature at 76o+2oF with RH 50 to 60%
Air Cooling Air Cooling means evaporation of water. Whenever the climate is relatively dry, it allows the water to evaporate. In the process, and air loses heat and temperature and brings a cooling effect. The commercial name for air cooling is Desert Coolers. Ventilation is to circulate the air, i.e. to let the inside air out and fresh air inside. It can drive out odor and let in freshness which is most essential for health.
- Bedrooms are used mostly during night, except on holidays, when they may be used sometime during day also.
- The living room is generally used in the day time. Some times when entertaining, it may be used during late evenings also.
- Normally, air conditioning is used for 10 hrs in a day and should cost around Rs 50/ per sq ft per month for its running, over and above the cost of the equipment and maintenance.
- Air conditioning with fresh air circulation is a must. Therefore, for the bedrooms, one should not go for a window or split unit type Ac, which does not have a fresh air component, as 8 hours of closure of the room will add to fatigue on account of less oxygen. Unfortunately, fresh air knobs in most ACs are not used or they don’t perform.
- Running a fan and the AC simultaneously is a bad practice, indicative of improper planning or inadequate equipment.
- Provided the surroundings are not noisy, the noise level of the AC should be low.
- The place where the AC equipment is to be used should not be exposed to sun. The windows or doors facing the sun should be covered by thick curtains.
- Real economy could thus be achieved in power consumption, which could be as much as 30% in running as well as initial investment.
- The supply of cool air should be at such level and location that the entire room gets uniform temperature.
- While moving from an AC to a non AC area, take care to stay a little while at the entrance
- so that the change in temperature does not effect.
How To Calculate Capacity Requirement
If the slabs of the AC are not exposed, or alternatively well insulated with 40mm thermocole or 50mm fibreglass if exposed, and there is no additional heating equipment, or air being exhausted by the machine or by adjoining bathroom or kitchen, the evaluation can be done on the following basis provided the height is 10 ft or less
- 160 sq ft to 190 Sq ft = 1 Tr (outside temp 30o to 35oC)
- 30 sq ft to 150 sq ft = 1 Tr (outside temp 36o to 45oC)
- In the living room, for any party use, add up one ton for every 9 persons over and above the load calculated on account of the area consideration as mentioned above.
- For every additional foot of height, use .07 as a multiplying factor
Example 1 : For a 12 ft high ceiling, if the area of the bedroom is 250 sq ft, one will need :
- 1/140 x 250 = 1.75 ton with normal height
- Multiplying factor: 1.75 x 1 + (0.07×2) as 2ft is additional height
- 1.7 (1+.14) = 17 x 1.14 = 1.94 Tr, ie. 2 Tr.
Example 2 : An example of air conditioning of a residence having two bedrooms and a hall
- Assuming the residence requires all three rooms to be air conditioned
- Alternative 1 :4 window units of 1.5 tons each. Cost approx 4 x Rs 30000 = 1,20000/
- Alternative 2 : A split unit with 2 condensing units and 4 Fan coil units. One can operate the area in use for a maximum limit up to the capacity of 3 tons, unlike in the first alternative where you can use 6 tons.
- Costing of split Units : 2 x 37 = 74000 (complete Unit)
- 2 x 13 = 26000/ (additional FCU)
- Hence, we notice that using the Split Type Units is more economical with lower maintenance and energy costs. Noise in this alternative also will be considerably reduced, even though it will require ducting and false ceiling in certain areas.
Thumb Rules for Ventilation
- This is mostly used in the kitchens or bathrooms to get rid of bad smell, fumes and heat, etc.
- In the bathroom, normally an exhaust fan is used just above the widows. Hence, that provides the least circulation. The fan should actually be at a higher level, whereas the opening for the fresh air in the form of window or ventilation should be one feet above the floor level, thus allowing the circulation to be complete.
- If the bathroom has a door or wall facing the exterior, it is better to provide the exhaust opening there.
- In the kitchen ventilation, the fumes are to be picked up immediately from where the cooking is being done and exhausted out. Hence, and exhaust fan near the windows will not provide adequate protection.
- If a hood is being used for fumes, then ducting it out is definitely better than providing exhaust fans.
- Normally frames are used for cooking where there is no cross ventilation, so that it does not affect the frame. Hence, it becomes necessary to plan the ventilation of the kitchen more scientifically.
- Ventilation of the kitchen should be done in such a manner that no additional ceiling fan is required and air circulation should cool the occupants of the kitchen.
- The exhaust hood used in the kitchen should have an oil trap, preventing the oil to reach the exhaust fan.
- A good ventilation system in the kitchen adds to the life of the refrigerator, deep freezer and other electric appliances. It also increases the life of the painting in the kitchen.
Thumb Rules for Air Cooling
- Whenever humidity is upto 50%, air cooling / desert coolers can work effectively.
- Water available in the desert coolers should have no foul smell, as it can be carried forward to the entire house.
- Those who have sinus or cold, should remain away from the humid area. They can not use air cooling, as the humidity level is around 75%, when the machine is in operation.
- While using a desert cooler, don’t use only the fan, as the hot slab will send hot waves of air thus nullifying the effect of air cooling.
- The drop in temperature can vary from 78oC to 15oC depending on the outside temperature and humidity. During the monsoons, the effect of the desert cooler is reduced.
- For a normal bedroom with a 10 ft high ceiling, a 1200 CFM fan in the desert cooler is required, while for the hall, a 2000 CFM is needed.
- In large bungalows, air cooling can be achieved by a central system with the help of ducting. No return air is required, as the entire cool air is pushed out automatically. Thus it provides ventilation along with cooling.
- A major disadvantage of air cooling is that, the noise level is higher than an AC and humidity control is negligible.
By Rajan Bahri
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