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How do I Know if the Cooling Load for My Air Conditioner Was Calculated Incorrectly?

One of the most common air conditioning issues we encounter in the Arlington, VA, area is incorrect sizing. We at HVAC & Plumbing Unlimited can tell you that a properly sized system is an efficient and effective system; going either too big or too small can have huge consequences for your comfort and your budget. Here are a few ways to determine whether your air conditioning system has been properly sized.

A/C Load Calculation: Rules of Thumb

In the past, many HVAC contractors have used simple rules of thumb to calculate sizing for home air conditioning systems, ignoring other factors and just using square footage to come up with a load calculation. While leaving out insulation, load-creating appliances and other factors makes these rules inaccurate, the biggest issue is that many HVAC professionals have used bad rules of thumb. Many homes have systems with one ton of power per 400 or 600 square feet; in reality, the most accurate approach is to have one ton per 1,000 square feet. This means many home air conditioning systems are grossly over-sized.

By using this rule of thumb in reverse, you can identify whether your cooling system is at least in the right ballpark. If your home is 3,000 square feet and your unit has three tons of cooling power, for instance, the original load calculation was probably pretty close to accurate. Conversely, if you have a five- or six-ton system, the sizing is almost certainly wrong.

Performance Issues

A fairly accurate way to spot an over-sized unit is to observe the way it operates. If your cooling system has too much cooling power, it will frequently overshoot your desired temperature, forcing it to constantly cycle on and off. Most air conditioners will cycle occasionally during the cooling season, but if it happens several times an hour, you likely have an over-sized system. Note, however, that frequent cycling can also be caused by maintenance issues, so check the wiring for any interruptions in the power supply before blaming sizing.

As a rule, a properly sized air conditioner should run continuously on the hottest day of the year. If your cooling system is constantly turning on and off even during the height of the summer, odds are good that it is too big for your home.

Next Steps: Schedule a Professional Load Calculation

If you have reason to suspect that your air conditioning system may be improperly sized, don’t delay. A professional room-by-room analysis will determine whether you actually need a larger or smaller unit. We at HVAC & Plumbing Unlimited will be able to recommend a new system that actually meets your home’s cooling needs with no wasted power and no wasted electricity. Give us a call today, and we’ll be more than happy to send a technician to your home to assess your cooling needs.

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