Refrigerant travels with the lubricating oil through an a/c system. When the condenser is out-of-level, the oil can separate and the compressor may operate without adequate lubrication. Most manufacturer installation manuals specify that the unit be mounted on a level surface. When we called tech support at Goodman Manufacturing (maker of both Goodman and Amana air conditioning systems) to find out what the acceptable tolerance was for leveling a heat pump or air conditioning condenser, the answer we got was “level means level.” They did not offer any range of deviation for a condenser to tilt and still be acceptable. 

   While we are sure that slightly out-of-level is not a problem, if a condenser is noticeably leaning we put a SmartTool® on it to define how far it’s leaning and write it up in our home inspection report. The condenser shown at the top of the page was leaning an excessive 12.2º, but it is typical to see an older condenser leaning 4º or more on a sloped site with soil subsidence, as shown below.

     A diligent a/c contractor will install to the manufacturer’s specs, but soil subsidence from roof rainwater runoff will cause the ground to shift under the pad over time. A mounting pad elevates the base of the unit a minimum of three inches above the ground at installation and, unfortunately, the settlement is often accompanied by the pad sinking into the dirt. The minor vibration generated by a condenser, combined with its weight, creates a low-energy, but repetitive tamping action that can slowly ease the condenser pad into the soil a little over time.

    Other manufacturer standards for installation relate to clearance around the condenser for heat dissipation. Typically, a minimum of one foot clear around the sides and five feet above it is specified. Also, installing a condenser at an inside corner is not recommended because of the reduced natural air circulation. 

    Also, see our blog posts What is the best location for a heat pump condenser (outside unit)? and Does the mounting pad have to be replaced to install at new heat pump or air conditioner condenser 

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  To learn more about heating and air conditioning systems, see these other blog posts:

• How can I find out the SEER of my air conditioner? 

• My air conditioner won't turn on. What's wrong? 

• How can I find out the size of my air conditioner? 

• How can I tell whether the condenser (outdoor unit) is an air conditioner or heat pump? 

• Where is the air filter for my central air conditioner and furnace? I can’t find it? 

• Does an old air conditioner use more electricity as it ages? 

• How did homes stay cool in Florida before air conditioning? 

• What is wrong with an air conditioner when the air flow out of the vents is low?

• Why has the thermostat screen gone blank? 

• Why does it take so long to cool a house when an air conditioner has been off for a while? 

• Why is my air conditioner not cooling enough? 

• What are the most common problems with wall/window air conditioners?  

• Will closing doors reduce my heating and cooling costs? 

   Visit our HEATING AND AIR CONDITIONING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.