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Hi, Summer! We’ve missed you. The beach parties are back in session, your XL cooler is sanitized and ready for cold ones, and your grill is stocked with propane for days. But, before you get too drunk on summertime fantasy, we have a buzz-kill topic to discuss. Your HVAC. Ever come home after a long day in the sun, middle of August, super excited to relax in your chilled living room, only to walk into heavy, thick, balmy, and stale air? Your A/C has decided it’s time for a vacation. Although these things happen, one factor that you can control may help avoid this smoldering nightmare altogether: The actual size of your system.

How to determine the right size?

Math. The Air Conditioning Contractor’s Association of America has a specific equation that matches the size of the A/C with the home’s load calculations. This approach is called “Manual J” and is incredibly accurate. This load calculation is required by code officials for a builder to get a permit. If you are not in a new house, ask your HVAC technician to run this calculation for you. Factors considered in this calculation are square footage, types of windows, type of insulation, and climate to name a few.

Bigger isn’t better?

Not necessarily when it comes to your HVAC system. Unfortunately, a contractor or HVAC technician may try to skip the Manual J. Units are sold by the ton, so the bigger the unit you buy, the more costly. A consumer can easily assume that the bigger the system, the better it will accommodate your space and keep you cool. An A/C unit accounts for roughly 50% of your electric bill but 100% of your comfort. Think of it as an automobile – miles per gallon don’t go as far if your engine is oversized.

Problems with an oversized unit:

  • Poor efficiency = higher energy bills.
  • Wear and tear on your oversized A/C will exasperate. A proper-sized system will run for long, even cycles. But a larger-than-necessary system will run on short cycles, starting up and stopping far more. This could very well mean a shorter life and/or expensive repairs.
  • Short cycles could mean some rooms are far cooler than others.
  • Humidity levels will be higher with an oversized unit as those short cycles with low air circulation will leave your home clammy.
  • Mildew, due to the aforementioned humidity. This bigger-than-needed unit is so quickly cooling the space and not allowing enough time to remove the moisture from the air = mold!

Be sure.

Before you and your family are in agony over a kaput A/C, opt to have an independent inspector come and take a look at your unit. Run the Manual J and ensure your home is equipped with the proper sized unit. Future sweaty you will thank present comfortable you.