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