Should my HVAC unit be shaded?

Increase air conditioning efficiency with shade

The Shade Debate has been going on for years, between customers, scientists, and HVAC technicians. The question is, whether or not shading your condenser (that big steel box with the fan that sits outside of your house and begins the air cooling process) actually makes a difference in the efficiency of your system. Sure, if you shade your condenser, you can feel with your own hand that the cover is cooler to the touch. But does it matter? Read on…

What happens:

 Outside air is what the condenser uses for heat transfer. When your outside fan turns on to cause air to flow over the outdoor heat exchange coils, it moves a huge amount of air. A 3-ton condenser moves hundreds of thousands of cubic feet of air in an hour. While there may be a thin amount of air that is slightly cooler if your system is in the shade, the amount is so small that it doesn’t make a difference to the system as that little bit of air that may have been shaded will be mixed up with all the rest of the air the fan is moving.

So because the outside air is what actually transfers the heat, the system itself becoming slightly warmer from the sun is not detrimental to it running nor does it affect the cooling of your air.

Also, because this hypothetical system is outside where the air is naturally flowing anyway, shading the air around the system will not be helpful because that air will be naturally moving away from the system when a breeze blows or air just naturally moves out of the area.

But, what about the actual parts of the condenser heating up in the sun?

Of course, if you shade the condenser, it will reduce heat to the cover. But inside the cover, even in full sun, the cover isn’t conducting much heat to the actual system. But it is shading it. So while the cover is keeping your system shaded, adding more shade is basically just shading the cover itself, and it’s designed to take the heat.

According to researcher Danny Parker from the Florida Solar Energy Center, who performed a two-year energy study, shading the unit provides “minuscule results at best” with efficiency being increased less than half a percent.

While you may wish to cover your condenser since let’s face it – they aren’t very stylish! You don’t want to smother it. According to research by the Kuwait Center for Scientific Research in their paper, “Effectiveness of Shading Air-Cooled Condensers of Air-Conditioning Systems”, foliage, trellises, walls, or other shading devices too close to the condenser can cause restricted airflow, as well as causing hot exhaust air to be recycled back through the system, so it is processing an even warmer air than usual, reducing efficiency.

If you’re located in Florida, like we are, the difference shading your unit will make is actually smaller because of the higher ambient temperature. Overall, their research shows that “the actual efficiency improvement due to shading is not expected to exceed 1%”.

In addition, if you use plants to shade your condenser, you will need to keep the area clean of debris like leaves, twigs and clippings to prevent them from blocking fan blades or airflow and reducing efficiency that way.

So what would need to be done to make shading the condenser actually work?

You would have to build a huge room, just for the condenser, and keep the air contained within that area so that all of the air the condenser processes would be cooled, not just the thin layer of air under the cover. Because of all the exorbitant cost of building a room just for your condenser, there’s no way that would increase efficiency or be cost-effective.

Some people over the years have developed a routine of spraying down their air conditioner when they water their plants to “cool” it. This is unnecessary and doesn’t help the environment or your utility bill!

So the people who thought shading the condenser would keep it cooler, weren’t technically wrong – it can increase efficiency by as much as 1%. But considering all the factors, this amount isn’t enough to warrant building sun protection for your condenser.

There is an exception to this rule, however, and that is with the small, window unit sized air conditioners designed to cool just one room. These move much less air, are generally less powerful, and don’t come with a separate condenser and steel cover. As such these little guys can use the added help of shade. Their efficiency can actually be increased by about 10% by shading them.

Note:

Shading your condenser is not to be confused with shading your actual home. Shading the rooms of your house and considering the placement of trees can certainly contribute to an overall cooler home in warm months as well as a reduced utility bill. Deciduous trees that shed their leaves each fall & winter are nature’s helpful house shaders – your home will be cooler when shaded by thick leaves in Summer and the bare branches in Winter allow for the sun to shine through and warm your home.

Conversely, if you’ve ever wondered whether covering your HVAC condenser as it gets colder out would help, we think of this as a two-season answer.

While it’s not completely necessary, you can cover your condenser in the Fall once you’re done using the cooling feature for the year. The heating aspects of your system are not located here, and while the steel condenser cover is designed to withstand snow, rain, and wind of Winter, the Fall season presents a different set of obstacles, literally. Fallen leaves, twigs, berries and seed pods can collect moisture inside of the unit which can corrode the metal.

In Winter, you may wish to remove the cover, once the leaves, etc. are done falling. A cover provides a perfect place for rodents and other creatures to take shelter during the winter, and their nests and existence in your condenser would obviously not be good for it. So with these two seasons, it’s up to you. If you have a lot of trees and landscaping that causes debris to fall during Autumn, you may wish to consider covering the top. As always, feel free to contact us here through our site or give us a call if you have questions about what’s right for your HVAC system!

 

 

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