When I first started doing heating and air conditioning and someone needed a new hvac system, I was always told to get the existing model number (size) of the system currently installed at the property so the office could generate a quote to replace that system. Following this practice, I would say that 50% of those clients subjected to that process had issues/complaints about the new equipment and the way it performed. I didn't have the knowledge to understand why these were issues with newly installed equipment so I always grasped at straws, trying to find solutions. The funny thing about solutions is, without the proper knowledge; it's usually a very frustrating experience especially if you truly care about your craft. This trend continued for many years of my career until I got introduced to the best tool I've ever found.
I was introduced to the HVAC School community created by Bryan Orr (Co founder of Kalos Services and creator of the HVAC School podcast, website, and other platforms). It was through this community that I established relationships with great minds from around the world who understood exactly why I was dealing with issues related to brand new equipment. I started diving deeper and deeper down the rabbit whole of equipment sizing and a series of manuals written by the ACCA such as the manual J, S, and D. These manuals are engineer manuals (holy grail if you will), that facilitate the perfect, healthy, and comfortable application of HVAC equipment. It took me many years to even become competent (far from an expert), with these manuals and how to apply the information contained within; as a matter of fact to this day I continue to learn new things from these manuals everyday! It was within these manuals that I found the errors of my ways as well as the solution I was looking for.
The ACCA manual J teaches how to perform a proper load calculation, that means what is the right size equipment to install in order to get the desired outcome. The engineers don't necessarily outline the "why" in these manuals, however; I will share that shortly. Proper sizing of HVAC equipment is a very complexed process that can become convoluted should one want to dive deeper and deeper. The process of obtaining a 70%+ accurate load calculation is not that difficult and realistically takes very little time, but a good understanding of what you are doing none the less.
The "why is it important" was answered for me by my relationship with the HVAC 2.0 community and specifically Nate Adams. Nate wrote a book called the Home Comfort Guide where in the easiest to understand way, he explains the importance of a properly designed and installed HVAC system. A properly designed and installed HVAC system delivers energy efficiency, even heating and cooling of a space, perfect moisture control, extended equipment life, reduced cost of installation and maintenance, and overall comfort.
As I started doing better and better load calculations, I found that 90%-98% of existing installs were oversized. One might ask "is that such a bad thing?". Oversized equipment consumes more energy, doesn't remove moisture properly, breaks down more frequently, and COSTS MORE TO INSTALL! Bigger equipment cost more to install than smaller equipment, so the number 1 concern that consumers have which is the cost of new equipment can be immediately reduced just by installing the right system. Then there's the frequency of repairs needed for oversized equipment, costing consumers even more money. From a business standpoint, I guess I should do what everyone else does and install oversized equipment... but my ethics and knowledge won't allow that. So I'll just stick to the plan and finish this blog.
Living and operating a business in coastal North Carolina, we deal with a tremendous moisture issue. Moisture accounts for a major part of our load calculations, so much so that depending on the infiltration rate of a structure, moisture alone can account for up to 33% of our equipment sizing (this is in the most extreme cases of very leaky houses). Humidity has a greater effect on how we "feel" in our homes than the actual temperature. Don't believe me? Start measuring your indoor dew point and relative humidity at night in the spring, summer, and fall. Once you find consistent dew points above 60 degrees, get a portable dehumidifier to bring that dew point down; then let me know how you feel. At that point, you'll be asking me for a new HVAC system cause you will love the comfort and hate dumping that dehumidifier bucket out every 3 hours.
The last thing I will hit on here is going to be the energy usage of equipment. I was taught (before I knew what I was doing), to sell high efficiency equipment with the basis that it would drastically reduce energy bills. It can... if sized properly, on a proper duct system, and installed correctly. Notice there are 3 caveats to efficiency? I recall working for a contractor back around 2018 and going to a home roughly 1000 sq ft in Jacksonville NC and they had an old 1997, 8 seer, 1.5 ton heat pump. It had a refrigerant leak in a coil that was no longer available, so it was time for a new system. The owner of the company never performed a load calculation, never assessed the duct system, just told me to sell them an 18 seer 2 ton heat pump... so I did. They were told that their electric bills would go down, the system would be super quiet, and they would be extremely comfortable. The occupants had just retired and have a severance package they used to pay for this install. Fast forward a month and the system was locked on a failed blower communication fault (this actually continued to happen many many times over the course of a year). The indoor humidity stayed above acceptable levels and the air handler (installed in a closet) was extremely noisy. The system would constantly generate error codes for high static pressure and operation issues. Static pressure is like blood pressure for your HVAC, the higher it is; the closer to death you get! The equipment wasn't the issue and technically the installation wasn't either, the ducts were. One could argue that the system was oversized in this case, and it kind of was, but there's more to that statement that I can cover in another blog later. The duct system was older and designed for not only a smaller system, but also a different style of blower motor that was engineered to operate at a much higher static pressure than the new system. Had the ducts been properly designed and replaced, they probably would have loved this system. To top it all off, their electric bills went up!
Proper equipment sizing and installation are imperative to being a happy consumer and not regretting your hvac system. Please don't tell my competition this, since my ethics are in check, the only way I can make a living right now is by cleaning up the messes I find. If everyone starts installing good systems and duct work, I'll have to become a lawyer or something like that. I hope you enjoy reading this, I hope it helps, and feel free to leave a comment and follow us on facebook. Thank you.
Kenneth Casebier
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