Standard 183 was created in a collaborative effort between ASHRAE and ACCA, the Air Conditioning Contractors of America. It establishes minimum requirements for performing peak cooling and heating load calculations for buildings except low-rise residential buildings. Although there are many methods available to perform peak cooling and heating load calculations, the intent of this standard is to establish a minimum level of requirements that is as inclusive of as many methods as possible while still being restrictive enough to mandate an appropriate level of care and accuracy. An accurate estimate of peak cooling or heating load requires not only that a sound method be used but also that inputs to the method are reasonable and realistic (the execution of the method).
The heat transfer interactions that occur outside and inside a conditioned building are complex and involve many interrelated variables. All load calculation methods therefore involve some level of simplification of the actual interactions among these variables to allow practical solutions to these very complex problems. The requirements in this standard that relate to the load calculation method are technical to the extent that they address these simplifications of the fundamental heat transfer interactions. If a method oversimplifies the problem, then an inaccurate load estimate can result. Complying with this standard requires knowledge of the underlying principles of the methods used and the techniques that these methods use to address the fundamental heat transfer interactions.
There is a distinction in this standard between zone load and system load. This standard is intended to address the calculation of zone load, but it is impossible to completely decouple the system load or capacity calculation from the zone load calculation. Systems and the processes to calculate their loads or capacities vary dramatically. Some aspects of the overall approach to systems are included in this standard, but the standard is not intended to be a comprehensive or detailed discussion of how to calculate system loads. Users of this standard are cautioned not to confuse zone heat gain with system sizing.