If you’re confused by the way A/C capacity is measured, you’re not alone. Though a system’s capacity is measured in tons, this isn’t a reference to the weight of your HVAC system.
Why do we rate A/C capacity in tons?
Back before air conditioning, people cooled buildings in the summer with ice harvested from lakes and rivers in the winter, and the crop of ice extracted from a river was measured in tons. Somewhere along the line, this term was institutionalized and remains in use today.
But we don’t use ice anymore, so how do you explain A/C capacity?
A 4-ton A/C unit doesn’t weigh 8,000 pounds. Though A/C capacity is measured in tons, this number is actually referring to how much heat the air conditioner can remove from your home in an hour. A 4-ton air conditioner can remove 48,000 British thermal units (BTUs) of heat per hour from your house.
Actual versus nominal capacity
There are two different ways to look at capacity.
- Nominal capacity: To avoid confusion, fixed room and outdoor temperatures are used when rating A/C systems for the sake of uniformity. Using these specific test conditions, nominal capacity ratings are obtained. For instance, a typical 3-ton system has a nominal capacity of 36,000 BTU/hour.
- Actual capacity: Actual indoor and outdoor temperatures will vary from the nominal testing conditions. Factors such as higher outdoor temperatures can result in lower actual capacity ratings when this same system is used in your home, lowering nominal ratings to an actual capacity of 2.8 tons.
What does this mean for me?
The nominal and actual ratings are rarely the same, and since AHRI’s operating conditions often aren’t comparable to the conditions your A/C system is operating under, its capacity may be even lower than it’s rated. In addition, issues with ductwork, dirty air filters or coils, poor airflow and improper refrigerant charge can also effect capacity.
Still confused about A/C capacity and how much you need to cool your home? Contact the experts at Apollo Home Heating, Cooling and Plumbing. Family-owned and operated since 1910, we offer the best customer service in the greater Cincinnati area.
Image via Shutterstock.com
"Ernie & Mike did a superb job on my new furnace and A/C installation. Despite having more than a day’s work to do, they came in and stayed until the job was done. They were organized, efficient, and protected the rest of the house well. Got both furnace and A/C installed the same day. Ernie was courteous, informative, and clearly knew his job better than anyone I’ve encountered before. The units look so good guests now get The Tour of our new system. Apollo is clearly not a fly-by-night company. I would recommend them to anyone in need of a new furnace and/or A/C."
- Jerry A.
"I called Apollo because of a water leak I thought I had in our upstairs shower going into the kitchen. Robbie came and assured me everything was fine & looked at all the other plumbing. He ended up changing a few pipes for our washer & clearing a drain. He was very nice & knowledgeable with all my questions. I ended up signing up for the care plan & was very happy with my service."
- Cassandra B.
"The team at Apollo exceeded my expectations. As a business owner, my attention to the details and commitment to providing excellent service is high. From the sales rep. to the installation team, everyone’s performance was outstanding. For example, the installation team went to great lengths to protect our floors, placing floor runners and across the wood floors and up the stairs. They even were spot washing walls upon their departure. I highly recommend this company."
- Randy B.
"We scheduled an estimate AND a tune-up. We knew something was wrong with our furnace, but hoped we could make it through the rest of the season. Upon telling Bill what our furnace was doing, he warned us immediately what the possible outcome was going to be; a cracked heat exchanger. He watched the flames roll backward, tested carbon monoxide levels, which were so high they meter’s last reading was 5,600 before saying “high”. He immediately shut it down, tagged it, and explained that with levels that high and children in our home he wanted off right away. He continued his inspection and showed us via a camera that not only was it cracked in multiple places, but had holes all over it. He gave us a few options for repairing it; his knowledge as well as genuine concern was beneficial and refreshing. Luckily we also scheduled an estimator, Micah, to come too and we were able to get costs between repairing and replacing (with several options). We decided to replace with a much higher efficiency furnace and one sized properly to our home. Hands down, not only did they both provide us great service and knowledge, but without sounding dramatic, they may have saved our lives. This was our first time calling Apollo, but it won’t be our last."
- Sarah B.
"Apollo is an excellent company. I always receive great service. Alex A. was professional and friendly. He kept me informed during the process of checking my furnace and heat pump to make sure they were working properly. The company makes sure you are notified who is coming and when they are on the way. All my interactions with the company have been wonderful."
- Beverly S.