Managing Your HVAC System

Is It Normal For Your AC To Struggle In Hot Weather?

There's no question that the hottest days of summer are also some of the hardest times for your air conditioning system. Even if you keep your thermostat set relatively high, your air conditioner still must deal with a substantial difference between the temperature outside and your desired interior temperature.

HVAC technicians can examine this by looking at the temperature difference between your return ductwork and supply vents. By producing air that's continually colder at the supply than the return, your AC system ultimately helps to bring your home's temperature in line with your thermostat setting. But what happens when your AC seems to struggle when the exterior temperatures become extreme?

The Meaning and Importance of Delta T

If you've taken calculus classes, you might see "delta T" and start sweating for reasons other than a struggling air conditioning system. Fortunately, this term comes with a different meaning in the HVAC world. The Greek letter delta typically refers to a change in some value; in this case, delta T refers to the change in temperature between supply and return air.

No single value is correct for an air conditioning system's delta T. Specifications can vary from manufacturer to manufacturer, although they do tend to cluster around similar values. If your air conditioning is struggling to keep up with outside temperatures, one of the first things an HVAC technician will do is check your current delta T against the expected value for your system.

This reading provides critical information for further diagnosis,  which is why contractors often use it as a starting point.

Why Delta T Matters When Your System is Struggling

There are typically three reasons that a system may struggle as exterior temperatures increase:

  • Maintenance or repair issues
  • Undersized capacity
  • Home efficiency issues

None of these conditions are normal, and the delta T can help your contractor find which one may be to blame for a struggling unit. For example, if your AC is producing the correct delta T, the problem may be that your home is losing cool air faster than your AC can keep up. You may also have an airflow restriction preventing cooler air from reaching everywhere in your house.

On the other hand, a delta T that's noticeably below your system's rated specifications often points to an underlying issue. Your system may be low on coolant, causing the evaporator to freeze and forcing the compressor to shut down too soon. You may even have too much airflow moving across the evaporator coils, preventing them from efficiently absorbing heat.

Using this information, an experienced professional can help you determine the cause of your struggling AC and help you find a solution. Whatever the case, a correctly-designed AC system should never struggle to keep up on hot days, so it's worth calling in a technician if you notice your interior temperatures creeping up as the outside temperatures soar.

Reach out to an AC system repair company for more information.