subject: Acca Certified Heating & Cooling System Design - Manual J, S & D - The Basics [print this page] The correct design of a HVAC system involves more than simply picking out the biggest air conditioner and furnace available. In order to get the most efficiency it is important that a contractor use all the tools at their disposal in choosing the correct size of an HVAC system. The first step is to use ACCA certified Manual J load calculations in order to determine the heat loss and heat gain of a particular home. Calculate correct cfm for each room and total for building for both supply and return. This information can help a professional to evaluate the needs and requirements of a building in order to choose the most effective system.
Using the information provided by a Manual J report, a contractor is able to then use Manual D in order to determine the proper layout for the duct work. The report can help them to determine the most efficient way to run the duct work as well as the size to use in order to provide the maximum heating and cooling to each room in the home or building. This is an important step that is overlooked the by many homeowners. Put simply, smaller rooms do not require the same amount of cool or warm air as larger rooms do.
Using Manual S, a contractor will determine the proper HVAC equipment. A furnace or air conditioner that is oversized or too large for the intended building will not operate efficiently. The same is true for equipment that is undersized as it will strain to keep up with the demands of the occupants. Size HVAC equipment to sensible load using ACCA Manual S procedures. From Manual J loads and Manual D cfm, determine appropriate equipment. Equipment should be sized to total loads. Equipment total capacity should not be more than 15% larger than the total design load (as specified in Manual S).
The correct equipment will provide the most efficient heating and cooling using the minimal amount of energy and will deliver a consistent and comfortable temperature. The proper selection of heating and cooling equipment can reduce energy usage as well as the cost of operation.
Size duct system according to ACCA Manual D calculation procedures. Lay out duct system on the floor plan and determine register positions and duct paths to optimize room air circulation and minimize the length of the duct. Duct paths must account for locations and directions of joists, roof hips, fire walls, and other potential obstructions. Duct paths must be planned to avoid sharp turns of flexduct that will kink the duct. Choose registers to optimize air distribution and duct static pressure. For return-filter grills, calculate minimum return filter area per Manual D.
A qualified and professional contractor will use Manual J, S and D in order to deliver the best possible product for the homeowner's needs. It is a comprehensive approach that will produce the most outstanding results possible. Coming up with an efficient HVAC design does not happen by accident and requires an individual who is knowledgeable in the industry.
The right system can provide years of dependable and consistent use while lowering the utility costs for the homeowner. These days no one can afford to throw away money on an inefficient heating or cooling system, not to mention the fact that it is hard to be comfortable if your home is too hot or too cold.
