What You Need to Know About Installing AC Condensers

Where should you install a central air conditioning system's condenser? If you're new to AC, take a look at some condenser installation questions that homeowners have.

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What Is an Air Conditioner Condenser?

The condenser does exactly what the name implies &#; it condenses. While condensing is a broad term, in the context of your home's air conditioner, this refers to the ability of the unit to condense refrigerant vapor back into a cool liquid.

How does this process happen? The air conditioner:

• Has an indoor coil. Also known as the evaporator, chemical refrigerant circulates through this interior space and absorbs the heat.
• Moves the vapor to the condenser. The heated vapor travels to the condenser unit for cooling via a compressor.
• Cools the vapor. The condenser turns the gaseous refrigerant vapor back into a liquid for reuse. After the refrigerant reverts back to its liquid state, it leaves the condenser unit and makes its way back into the central part of the AC system.

Now that you know how the condenser works, learn more about where it needs to go in relation to the rest of your air conditioning system.

Where Is the Condenser Located?

Central air conditioners and mini-split ductless systems use an indoor-outdoor approach to home cooling. In a central AC system, this includes the indoor evaporator coil and the outdoor condenser. The condenser should always go outside of your home and not in an attic, basement, garage, or crawl space.

Why does the condenser need to go outside of your home? The top reasons include:

• Air supply. The condenser needs an adequate air supply to cool the refrigerant and do its job. Without enough outdoor air, it won't work efficiently.
• Airflow. Not only does the condenser require enough air to function properly, but it also needs plenty of airflow. You won't find a suitable natural flow indoors.
• Heat. The outdoor placement provides plenty of space for the condenser to release the heat. An indoor location can cause excessive heating of your home's interior, which reduces the overall effectiveness of the AC system.

Even though your home's outdoor space is the general area you should place the air conditioner's condenser, you need to get specific and think thoroughly about the specific site.

What Should You Consider When Placing an AC Condenser?

The proper placement of an air conditioner's condenser can help the system function at peak efficiency and minimize potential damage or safety hazards.

Where should, or shouldn't, you place the condenser? Before you make a decision, consider:

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• The sun and heat. Will the condenser stand in the hot sun for most of the day? While a sunny spot won't necessarily ruin the system's ability to cool your home, a shaded area may help the unit to function more effectively.
• The trees in your yard. Even though a shady spot is ideal, a low-hanging tree or an older/infected tree can pose a damage risk. Branches, twigs, and bark can fall into the unit. This can result in ineffective cooling or ongoing odd noises.

• T

  he shrubs in your yard.

  Again, the condenser needs free-flowing air. If you're tempted to hide the unit behind a tight bunch of shrubs (or other plants), don't. Nearby plant life can crowd the condenser and limit airflow.

• The ground. The condenser requires a flat surface to function effectively. Avoid hills, dips, or bumpy soil. You may need to place a concrete pad on the ground to create an even surface for the condenser.
• Safety. Keep the condenser away from spaces your child or pet plays in regularly.

If you're still not sure where to install the condenser, talk to a professional. An HVAC contractor can evaluate your yard and help you to choose the proper placement.

Do you need a new air conditioner? Contact Comfort Technology Heating & Air Conditioning for more information.

© This excerpt taken from the article of the same name which appeared in ASHRAE Journal, vol. 61, no. 1, January .

By George Games, P.E., Member ASHRAE

About the Author
George Games, P.E., is a design engineer and owner/principal of North East HVAC Engineering and Consulting, LLC, in East Brunswick, N.J.

In , I wrote an article in the June issue of ASHRAE Journal about problematic installations of split system air-cooled DX condensing units. Here, I expand a bit on the same topic and offer a few more photo examples of other problematic installations. As with the previous article, what follows is a qualitative discussion supported by photos and a figure.

The previous article focused on the adverse effect on performance and cooling airflow through the units due to poor layout configurations. The poor layout configurations mentioned in that article included those due to units mounted too close to each other or too close to walls. It spoke to maintaining minimum space clearances around the units for proper cooling airflow.

Unit Airflow Quantity

Unimpeded airflow thru a condensing unit is extremely important as the amount of airflow the unit moves across its condenser coil surfaces is one factor that determines if the unit delivers its cooling capacity or not. The units are designed at the factory to move the selected &#;design&#; air quantity across its coils as required to achieve its intended rated capacity. This is done by selecting the right size fan and motor going into the unit. Various factors including the size of fan (in overall diameter), fan blade pitch, the number of fan blades and fan rpm determine the amount of airflow required by the unit. Also, there are considerations taken at the factory of how obstructions might affect the amount of this airflow moving through the unit. At the factory, it is assumed that obstructions external to the unit that might block or impede airflow, will largely be non-existent at the installed site. Therefore, the factory always specifies that the unit be installed with minimum space clearances (around the unit and above it) to ensure any obstructions do not affect, lower or block the required airflow from entering or leaving the unit while operating. These minimum clearances are found in the equipment&#;s installing manuals. They must be followed.

As an example, two excerpts of installation instructions, from a major OEM follow. The first excerpt pertains to larger tonnage units and the second for smaller tonnage units.

For units sized from 10.4 to 25 tons (36.6 to 87.9 L/s):

1. &#;1. Minimum clearance for proper operation is 36&#; (914.4) from walls, shrubbery, privacy fences, etc. Minimum clearance between adjacent units is 72&#; (.8). Recommended service clearance 48&#; (.2).
2. 2. Top discharge area should be unrestricted for 100&#; () minimum. Unit should be placed so roof run-off water does not pour directly on unit.
3. 3. Outdoor air temperature sensor opening (do not block opening).&#;

For units sized from 1.5 to 10 tons (5.3 to 35 L/s):
&#;Top discharge area should be unrestricted for at least (5 feet) above unit. Unit should be placed so roof run-off water does not pour directly on unit, and should be at least 305 (12&#;) from wall, and all surrounding shrubbery on two sides, other two sides unrestricted.&#;

Thus, any obstruction or blockage anywhere, upstream of the unit, or downstream of it will affect the amount of airflow through the unit. It&#;s a simple relationship; a fan encountering a resistance greater than designed for, will ride up on its operating curve and deliver less air&#;greater resistance equals less flow.

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