There are several key differences in the goals and intentions behind the design and functionality of a residential HVAC system versus a commercial system in a large building with lots of people inside at any given moment. Although the basic logic and engineering from a home system is simply expanded upon and supplemented in bigger systems, there are several key factors that make designing commercial HVACs much more complicated. The main one is you building occupancy. Even if you have a family of four, unless you all live in a tiny cupboard sized apartment, the body heat of your family typically isn’t having a considerable effect on your HVAC performance, regardless of whether or not all of your are at home or none of you are. But in large buildings like superstores where hundreds of people are coming and going hour by hour, minute by minute, indoor occupancy levels actually have a considerable effect on that building’s AC performance. A small residential system is working against outdoor temperatures alongside the level of proficiency in your home’s heat installation. It is always going to have a harder time running at 12pm under full sun versus at 12am in pitch blackness no matter how many people are in the house. But this isn’t always the case with something like a large department store or an outlet mall. You have to consider air leakage in entryways, customer level peak times, heat exhaust from machinery, and any number of other variables in commercial settings. You don’t want your building to be so hot that customers are sweaty and miserable but you don’t want to see them shivering either. It’s about finding the balance between the two and maintaining that balance as much as possible.