| We hear a lot about air conditioner sizing, | | | | gymnasium with a lot of intense exercise?the |
| whenever we make the important choice of | | | | occupants. It takes a lot to cool a town hall |
| purchasing, or installing one. What does the | | | | full of people, doesn't it? Oh yes, we |
| word sizing really mean?Air conditioners are | | | | generate heat.Square feet method?You might |
| designed for heat removal, or addition (if | | | | have heard about the square feet method in |
| heat pump is included in the single package). | | | | air conditioner sizing. In fact, it is used |
| Therefore, the "size" of an AC, will be | | | | often by many contractors, that we sometimes |
| specified in terms of heat removal, or | | | | use it arbitrarily. This method have been |
| | | | generalised, and simplified by contractors, |
| addition capability.Units that we use for | | | | from sizing many ACs.The most common |
| air conditioner sizing, are BTU/hr (British | | | | relationship is, "1 ton for every 500 square |
| Thermal Units per hour), Ton, and Watts. Some | | | | feet of floor area". This method might work |
| countries utilise one unit, more than the | | | | for a contractor, working in a small area, |
| others, in air conditioner sizing.It is | | | | with similar type of houses or buildings, |
| excellent if you can remember the | | | | |
| relationship between BTU/hr, Ton, and Watts. | | | | and similar wall material.But, the |
| You can quickly gauge the AC size, in case if | | | | relationship will not work, if you change the |
| your friends use units - that are unfamiliar | | | | wall construction type, or if you move into a |
| to you;1 ton is equivalent to 12,000 BTU/hr. | | | | different area, with different climate. |
| And,12,000 BTU/hr is equivalent to 3,516 | | | | Simply said, this method of air conditioner |
| Watts - or 3.516 kW (kilo-Watts).Concept and | | | | sizing will only work for a confined group of |
| fundamental of air conditioner sizingIt is | | | | building, in a given area.However, this is |
| based on heat gain, and/or losses in a | | | | method is reasonably useful for installing |
| building. It is obvious that you will need to | | | | window, small split, or portable air |
| remove the amount of heat gain into your | | | | conditioners.Manual JNow, this is the way we |
| house - if it is hot outside. Similarly, | | | | should do air conditioner sizing. Manual J is |
| you'll need to add in the heat loss from your | | | | a database, with methodologies, formulas and |
| house - if outside temperature is cold.In | | | | guide for sizing and AC. This manual has been |
| short, heat gain and loss, must be equally | | | | developed by ACCA (Air Conditioning |
| balanced by heat removal, and addition, to | | | | Contractors of America) - with regular |
| get the desired room comfort that we | | | | reviews.It will provide you with necessary |
| want.What determines the amount of heat | | | | data for heat gain and heat loss |
| removal and/or addition that we want?It is | | | | calculations. Wall construction, building |
| determined by,the temperature difference | | | | orientation, infiltration, shading, number of |
| between outside temperature, and our desired | | | | occupants, the temperature you would like to |
| temperature. It is common sense that if you | | | | set, outside temperatures, are among the most |
| want a cool room, in a very hot climate, | | | | important values it will look for, for proper |
| you'll need to remove a lot of heat. On the | | | | air conditioner sizing.This is indeed, an |
| other hand, it does not take much to maintain | | | | extensive manual, which is used by certified |
| a cool room, on a mild daythe construction | | | | and experienced air conditioning |
| material, and arrangement of your building. | | | | contractors.Manual J is just a tool. The |
| Let's say, that you have two identical | | | | important things are, the values that are put |
| houses. One is build out of glass, and the | | | | in it. If we put in accurate values, then our |
| other out of brick, and well insulated.Of | | | | results will be come accurate. Otherwise, |
| course the one built with glass would require | | | | it's not going to help much.What are amongst |
| much more heat addition, or removal, compared | | | | the important information, you should have |
| to the other - given a same day.Two identical | | | | for air conditioner sizing using Manual J? |
| house, with different orientation with | | | | These are,required temperature range within |
| respect to the direction of sun rise and | | | | your space,approximate temperature |
| fall, will also influence the air conditioner | | | | distribution within your area, to find out |
| sizingthe surface area of the walls. The | | | | the number of months you have winter, summer, |
| larger the surface area - the more heat that | | | | and mild weathers,wall surface area and |
| can loose, or gain through it. Hence, effects | | | | material. Window surface area,any tinted |
| the AC size that you would needinfiltration | | | | window? Any insulated space?how many person |
| plays a part in determining our air | | | | is going to live within each space?what are |
| conditioner sizing. Door gaps, cracked | | | | the activities carried out throughout any |
| windows, chimneys - are the "doorways" for | | | | day? How much cooking? How much of hot water |
| air to enter from outside, into your living | | | | utilisation?orientation of your building, |
| space. Only you know how frustrating it can | | | | with respect to the sun's rise and fall |
| get, to feel a draft of chill, or hot air | | | | direction, and,sources of infiltrationPart II |
| from outsideactivities and other equipment | | | | or air conditioner sizing is coming soon... |
| within a building. Cooking? Hot bath? Is it a | | | | |