Load Calculation, It's The Only Way To Know...A load calculation is the process of determining the proper size of a furnace and/or air conditioner for a home. In the early days of the industry, hvac companies made an educated guess to determine the heat gain and loss for the home. The guess was based almost exclusively on the square footage of the home and was not even close to being accurate. The main concern of the hvac company was to make sure the unit was big enough so they would not be sued. Therefore, they usually installed a unit that was much bigger than required. Later, an organization called the Air Conditioning Contractors Of America was formed. They developed standards and a method to more accurately find the homes' heat gain and loss. It involved many complex mathematical equations and required a lot of time to perform. Therefore, most contractors did not use the system. With the age of computers, this process has become even more accurate and requires less time. The computer software takes into account every detail of the construction of the home and how it affects the heat gain and loss. The software is pretty expensive and therefore many contractors still guess and hope for the best.
One of the basic laws of thermodynamics is that heat moves from a warmer area to a colder area. When it is colder outside than inside the home, heat travels to the outside. The heat that travels to the outside is called heat loss. At the same time, heat is added to the home constantly by things such as appliances, the sun shining in a window, or people. If the heat being added by those sources is less than the heat escaping, then heat from another source must be added to maintain a desired temperature. The amount of heat that must be added is called the heat load. When it is hotter outside than inside, the heat from the outside travels to the inside of the home. That heat plus the heat from the internal sources mentioned above is referred to as the homes heat gain. To maintain a given temperature, this heat that is gained must be removed. The amount that must be removed is called the cooling load. A load calculation is the method used to find these heating and cooling loads. An improperly sized air conditioner can cost you in several ways. The comfort level of your home will be adversely affected with an improperly sized system. If the system is too small, you will not be able to adequately remove the sensible heat. (You will not get the temperature of the home to the desired setpoint.) If the system is too large, the unit will not run long enough to adequately remove latent heat. (The homes' air will have that sticky feeling because the humidity level of the air will remain too high.) Another way an improperly sized system will cost you is in the equipment purchase price. In general, the larger the size of the unit (in tons) the more it will cost. Therefore, with an oversized unit, you will buy excess cooling capacity that you will never use. An oversized unit will also cost you more to operate. This occurs due to the system efficieny. The efficiency rating (SEER) is given for a unit at design conditions and steady state operation. Typically the unit is about 10% less efficient from start up until steady state conditions exist. This steady state condition is not achieved until the unit has ran long enough to coat the indoor coil (evaporator) with condensation. This can take from five to fifteen minutes typically. The basic load calculation, called a block load, is used only to find the required unit size. It looks at the home as a whole and gives a total load. Several factors affect this such as: 1. the type of foundation 2. type and color of roof 3. insulation values in walls,floors,and ceilings 4. window type, location, and quantity 5. type, location, and quantity of exterior doors 6. desired temperature 7. the area in which you live 8. size of home This is only recommended for a single level home. Without at least performing a block load, the contractor is only guessing on the unit size. Are you tired of outrageous electric, gas, or other energy bills? Our energy conservation analysis will take you by the hand for a tour of the home. You will be able to find many do it yourself projects that can lower your energy bills. A more advanced version of load calculation requires more information such as individual room measurements. This is called a room by room calculation. This not only gives you the equipment size but also designs the duct system based on the needs of each room. This eliminates large temperature differences from room to room in the home. It results in a higher level of comfort. This is recommended for homes with more than one level. If this is not done, the result can be a large temperature difference between floors in the home. If you would like, we can provide this service. You can start by gathering the information and filling in the following request form. Then, you can email us a copy of your house plans to service@hvac-for-beginners.com **NOTE** Make sure that you mark the direction of north on the plans. You can also find house plans on line and email us the plan number and the site where you found them. THIS SERVICE WILL COST YOU $100 (USD). You can pay using the following BUY NOW button. You wil be taken to GOOGLE CHECKOUT and they will handle your order.
A load calculation is included in a home energy rating which is a powerful tool when shopping for a home. They can help you avoid some surprises when you get your energy bills.
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