Four Reasons to Avoid Oversizing HVAC Systems

If a smaller HVAC system works well, a bigger one will work better, right?

Wrong.

It may make intuitive sense that a bigger, more powerful system cools and heats better, but in the real world, that’s not always the case. In fact, a system with more tonnage and BTU than a space needs will likely cause more problems than it will solve.

Problems with Oversizing

There are several reasons why oversizing an HVAC unit isn’t a good idea.

1. Humidity – Cooling or heating isn’t your commercial HVAC system’s only job. To make your space comfortable, it also dehumidifies the air. An oversized HVAC system runs on shorter cycles, which are not as effective at decreasing humidity as longer cycles. As a result, even if your temperature is satisfied, without humidity being removed, your space will feel cold and clammy. Indoor air quality will suffer due to discomfort, mold, and other high humidity problems
2. Hot Spots – An oversized HVAC system can result in hot and cold spots throughout your space instead of consistent, comfortable heat. This is because the system will turn on and blast heat too much heat right around the registers, eventually tricking the thermostat into shutting off before the heat reaches all areas.
3. Wear and Tear – With an oversized system, HVAC cycles are shorter and more frequent. It’s turning on and off more frequently and wearing out its parts a lot faster than a properly sized unit would. You’ll end up with more repairs and a shorter system life overall.
4. Less Efficient – Another result of short, frequent cycles is that your system will use more energy than a property sized system, resulting in higher energy bills.

What Can You Do?

To avoid oversizing, never rely on a rule of thumb for sizing HVAC systems. The load must be precisely calculated, taking the circumstances of the space into account, including square footage, type of insulation, number of exterior walls, natural shade and more. For proper calculations, refer to your local HVAC contractor or engineering design firm.

Modine develops and manufactures HVAC systems to fit almost any commercial or residential space or application, helping ensure you have the right tonnage and BTU to make your indoor space as comfortable as it can be.