- On April 24, 2023
By the time you’re asking this question, it’s probably pretty hot outside in Phoenix. While Phoenix has been named one of the most livable cities in the United States, summer weather when your AC isn’t at the right temperature is not ideal. Unfortunately, though, you can’t just set your thermostat and expect to be instantly comfortable. It’s not magic. It’s science.
Here’s what you need to know about the science of air conditioning, HVAC temperature differential, and things you can do to make your home more comfortable.
The Science of Indoor Temperature Control
Without getting too deep into how an air conditioner works, let’s start by defining terms like “supply air” and “return air.” The supply vents are the homes that supply treated air to your home. This is the cool air you feel when you put your hand in front of a vent. It’s coming from your A/C unit and through your vents.
Then there are the vents that don’t have cool air coming out of them: the return vents. These vents take air in and send it through separate ductwork. It goes back to your A/C unit where it gets cooled, then gets routed back to the supply vents.
When you think about pushing the limits of air conditioning, one big consideration is how much you need to change the outside air temperature to make yourself and your family comfortable. It takes a better HVAC system to stay comfortable in the dog days of summer than it does when it’s 70°F outside during spring in Phoenix. Understanding what you’re asking of your air conditioner comes down to thinking about the temperature differential HVAC units run up against here in Arizona.
Temperature Differential HVAC
Sometimes during the hottest days of our summers, it might start to seem like your air conditioner just can’t keep up with the oppressive heat here in Phoenix. What you notice on those days is called the temperature differential. The temperature differential HVAC units achieve the difference between the intake and output. In other words, it’s the difference in temperature between the air outside and the air inside your home.
For example, imagine the outside air is 100°F, and your home is 70°F. In that case, your HVAC differential temperature is 30°F. If you raise your thermostat to 75°F, you shrink your HVAC temperature differential because you’re not asking it to change the air as much.
Now imagine it’s 110°F in Phoenix, and you want to keep your home at 65°F. In this scenario, your temperature differential goes all the way up to 45°F. Now you’re really asking your air conditioner to do a lot of work!
Pushing your HVAC temperature differential too far can put a lot of stress on your system. Most HVAC professionals will recommend that you don’t put the AC’s temperature differential too much over 20°F. Here in Phoenix, though, that just doesn’t fly. Are you supposed to let your inside air temperatures get above 90°F for about half of the month of July?
This is one of the reasons that life here is so hard on air conditioners. It’s why we’re such firm believers in the value of choosing premium equipment like Trane HVAC systems. It’s also why keeping up with A/C maintenance is so important.
Delta T Versus Temperature Differential HVAC
There’s an alternate definition of HVAC temperature differential. Some people use the phrase to talk about the difference between the return air and the supply air (instead of the difference between inside and outside temperatures). We refer to this temperature difference between the return air and supply air as Delta T.
You can measure your Delta T by taking the temperature at a supply vent and then at a return vent. The temperature at your return vent minus the temperature at your supply vent is the Delta T.
For example, imagine the air is going into the return vent at 75°F and coming out of the air supply vent at 60°F. This would mean your HVAC system is operating with a Delta T of 15°F.
Most health air conditioners are expected to be able to achieve Delta T levels of at least 15°F or more. If your system isn’t reaching the set temperature, and your supply air is less than 15°F cooler than your return air, you probably need to contact Howard Air and see what’s wrong.
Sometimes the problem is as simple as changing your dirty filter. Other times you might need significant repairs or even a replacement. In some cases, you can fix your problems just by changing your thermostat settings.
Programming Your Thermostat
There are a few ways you can program your thermostat to make things easier on your HVAC system during the dog days of summer here in Phoenix. One thing you can do is set your fan speed to high. The high speed keeps the air moving through your air conditioner as quickly as possible.
If your air conditioner has different settings like Heat, Cool, and Auto, it’s best to set it to Cool on those hot days. Some people keep it set to Auto all year long, but the Cool setting is better when you know there’s no chance you’ll need to warm the air up any time soon.
Finally, you can set your thermostat to run in the mornings before outside temperatures get too hot. This gets your home down to a comfortable temperature when the temperature differential isn’t as extreme. Your air conditioner doesn’t have to work quite as hard, and then you can try to maintain that temperature throughout the day.
Remember Old Ducts Effect Cooling
If your HVAC system is healthy, but your AC is still blowing warm air, it could be a problem with the ductwork. Leaky ducts let the cold air escape before it comes through the supply vents to where you need it. If your ductwork isn’t leaking, it might just be too small. Undersized ductwork doesn’t deliver enough air, which makes it hard to get the home cool.
Choose Howard Air for Your Phoenix Area Home’s AC Needs
Howard Air has served Chandler, Glendale, Scottsdale, and the surrounding areas for more than 40 years. We know what it takes to keep homes and businesses cool in the Valley of the Sun. If your air conditioner isn’t putting out cold enough air, let’s get in touch!!
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