Air Conditioning and Building Survey - Factors and Criterias involved

Air Conditioning and Building Survey 

Air Conditioning:

                    Air Conditioning is the process of treating air so as to change or control its temperature, humidity, cleanliness and proper distribution of air to meet the requirement of condition space. As the outside temperature and humidity is higher, the heat flows to the conditioned space and increases the temperature and humidity of space. Therefore, to maintain the comfort conditions, the quantum of heat, due to the difference in outside and inside conditions, is calculated and removed to maintain the comfortable conditions. Apart from above heat quantum, there is some more heat, generated in the space due to occupants, appliances, and lights, which increases the temperature and humidity of the conditioned space. The air is the medium which transfers the heat from conditioned space. Hence, an air handling equipment is selected which could transfer this heat to refrigeration equipments/ chilled water or subsequent systems. The load estimation is first very important and critical step in designing of an Air Conditioning System. Based on this estimation only, the subsequent Equipments/Systems are designed and selected. Hence, it is imperative to mention that wrong load estimation will lead to wrong designing/selection of Air Conditioning Systems. A wrong system shall not be able to maintain the comfortable conditions and ultimately very purpose of the air conditioning system shall be defeated.

                    Hence, the engineer in HVAC industry must have a thorough knowledge of methods and practices followed for estimating the load. 

Building Survey:

                Before the load can be estimated, it is imperative that a comprehensive survey be made to assure accurate evaluation of the load components. If the building facilities and the actual instantaneous load within a given mass of the building are carefully studied, an economical equipment selection and system design can result, and smooth, trouble free performance is then possible. The heat gain or loss is the amount of heat instantaneously coming into or going out of the space. The actual load is defined as that amount of heat, which is instantaneously added or removed by the equipment. The instantaneous heat gain and the actual load on the equipment will rarely be equal, because of the thermal inertia or storage effect of the building structures surrounding a conditioned space.

                An accurate survey of the load components of space to be air-conditioned is a basic requirement for a realistic estimate of cooling and heating loads. The following are the aspects of survey for load estimation:

* Mechanical drawings

* Architectural drawings

* Field sketches

* Physical study.

1. Orientation of Building:

            Location of the space to be air conditioned with respect to:

            a. Compass points - shall be affecting the sun and wind affects.

            b. Nearby Permanent structure - shall determine the shading effects

            c. Reflective surfaces - Water, sand and parking loads etc. These surfaces increase the surface (Wall or Glass) temperature of the condition space due to reflection of sunrays.

2. Space utilization:

            It is important to know the use of space. The space may be used for office(type of business carried out in office), hospital, restaurant, residential, departmental store and factory etc.

3. Physical dimension:

            Physical dimensions of the space such as Length, width, height of space, etc must be known.

4. Ceiling height:

            Floor to floor height, floor to ceiling, floor to suspended ceiling etc must be known.

5. Construction Material:

            Materials and thickness of walls, roofs, ceiling, floors, partitions, and their relative positions in the buildings must be known.

6. Surrounding Conditions:

            a. Exterior color of walls and roofs shaded by adjacent building or sunlit.

            b. Attic spaces - unvented or vented, gravity or forced ventilation.

            c. Surrounding spaces - conditioned or non conditioned. If non- conditioned, the temperature of adjacent non-conditioned spaces.

            d. Floor on ground, crawl space, basement etc.

7. Windows:

            a. size and location of windows, wood, PVC or metal frame etc.

            b. Type of glass, single or multipane.

            c. Type of shading, dimension of reveals and overhangs.

8. Doors:

            Location of doors, type of doors, size, and frequency of use.

9. Stairways, elevators, and escalators:

            Location, temperature of space if the space is open to unconditioned area. Horsepower of machinery, ventilated or not etc.

10. People:

            a. Number of people or occupants in space, duration of occupancy, nature of activity and any special concentration.

            b. At times, it is required to estimate the number of people on the basis of square feet per person, or on an average traffic.

11. Lighting:

            a. Wattage at peak point.

            b. Type - incandescent, fluorescent, recessed, exposed etc. If the lights are recessed, the type of airflow over the lights, exhaust, return or supply, should be anticipated.

            c. At times, it is required to estimate the wattage on a basis of watts per square feet, due to lack of exact information.

12. Motors:

                Location, nameplate and brake horsepower, and usage. The latter is of great significance and should be carefully evaluated. The power input to electric motors is not necessarily equal to the rated horsepower divided by the motor efficiency. Frequently these motors may be operating under a continuous overload, or may be operating at less than rated capacity. It is always advisable to measure the power input wherever possible. This is especially important in estimates for industrial installations where the motor machine load is normally a major portion of the cooling load.

13. Appliances, business machines, electronic equipments:

                a. Location, rated wattage, steam or gas consumption, hooded or unhooded kitchen equipments, exhaust air quantity installed or required, and usage.

                b. Greater accuracy may be obtained by measuring the power or gas input during times of peak loading.

                c. Electronic equipments often require individual air conditioning. The manufacturer's recommendation for temperature and humidity variation must be followed, and these requirements are often quite stringent.

14. Fresh Air:

                The outside fresh air is added to conditioned spaces to maintain the odor and to provide freshness to the occupants as per applicable codes or standards.

                * Based on cubic feet per minute(CFM) per person

                * Based on cubic feet per minute per square feet floor area

                * Based on specified Air Change per Hour(ACHR)

                * Based on ASHRAE(American Standards for Heating Refrigeration and Air conditioning Engineers) and relevant code recommendations.

15. Thermal storage:

                Includes system operating schedule (12, 16 or 24 hours per day) specifically during peak outdoor conditions, permissible temperature swing in space during a design day, nature of surface materials enclosing the space.

16. Continous or intermittent operation:

                Whether system be required to operate every business day during cooling season, or only occasionally, such as churches and ballrooms. If intermittent operation, determine duration of time available for pre-cooling or pull-down.

Access Full Free HVAC Course by Clicking on the link below 👇👇

Full Free HVAC Course - Click Here!!!