1. 2)the tent shape of an evaporator coil that had become so dirty that the coil surfaces are no longer visible, and the following photo shows what a clean evaporator coil looks like.

    You can pull out the filter located at the bottom of some air handlers and look up directly into the tent shape of the evaporator coil to check for any dirt/dust accumulation. If not, a service technician can open the unit to examine the coils.
       Unfortunately, cleaning a dirty evaporator coil is an expensive proposition, involving evacuating the refrigerant from the system, disconnecting the coil unit, washing and scrubbing away the dirt in a solvent solution, then reinstalling it  and reloading with refrigerant gas.
       Dirt accumulation at the condenser coil (outside unit) will also reduce the efficiency of your system, and the photo below shows a typical accumulation that needs cleaning.
       But it is rarely a big problem, with one exception: when the nearby exhaust for a clothes dryer blows lint onto the condenser coils. The building code now requires that dryer vents not terminate near an air conditioning condenser.
  2. 3)Refrigerant leak - The gradual leakage of refrigerant from the pressurized lines in the system will reduce the cooling ability down to zero over time. An average HVAC system chills the air coming out of the air handler to about 18º F cooler than the incoming air. But as the temperature split (difference between incoming and outgoing air) begins to descend, the only noticeable change at first is that the system takes longer to cool down the home. For example, if the temperature split drops to 9º F the system will still cool your home but it will run for twice as long—and use twice as much energy—to do it.
       A service technician can check the status of your refrigerant to verify if this is the problem. Because it is a sealed system, any loss of refrigerant indicates a leak; so, adding another shot of gas without locating and fixing the leak will only be a temporary solution.

  3. 4)Blocked condenser unit - The condenser needs a completely open area directly above it and a minimum of 12-inches cleared all around to efficiently dissipate the heat that is removed from your home into the air. A little intrusion on this zone will have only a minor effect on the system’s performance but, when when the condenser is completely surrounded by overgrown foliage, the cooling ability will be noticeably deteriorated.

  4. 5)Failing compressor - The compressor is the most important component in the condenser unit. It is also the one part of the system that uses the most energy. Compressors use more electricity as they get older, and then begin to cool less efficiently before finally failing completely. When you put your hand over the top of the condenser unit while it is running, you should feel air being blown upward that is hotter than the outdoor temperature. If not, it’s time to call an a/c service tech.

  5. 6)Undersize system - Air conditioning systems are sized to be able to keep the house comfortable (mid-70º range) on the hottest days of summer, but will have to run continuously to do it. If you, or the previous homeowner, enclosed the garage or back porch into a family room or extra bedroom, without upgrading to a larger a/c system, then it may not be adequate to comfortably cool the additional square footage in your home on the really hot days. A larger system, sized by your HVAC contractor, is the solution.

  6. 7)Thermostat set too low - If you set the thermostat to 65º on a hot day, as noted above, your system may not be big enough to handle a temperature differential it was not designed for.
        The record high temperatures during the summer months over the last few years, exceeding 100º F in some Sunbelt cities, is past the mid-90º parameter used for sizing most systems. So on those scorching hot days many systems will struggle to cool the house, even if the thermostat is set in a normal range.

  7. 8)Bad Thermostat - This can be difficult to determine without tech tools but, with the thermostat set at your normal comfort temperature, position yourself at a location in the house where you can hear when the air handler shuts off at the completion of a cooling cycle. If it shuts down before the temperature reaches what you are accustomed to, then it is likely that a sensor or circuit in the thermostat is malfunctioning.

  8. 9)Damaged ducts - Critters that get into the attic or crawl space will sometimes chew open holes in ducts. Also, workmen crawling around can collapse or tear open duct connections. Small areas of damage will not leak enough air to make a noticeable difference, but a large gap in a main supply duct will radically reduce the air supply and temperature in your home. If you open the attic hatch or door to the crawl space—depending on where your ducts are located—and it’s cooler in there than inside your home, investigate further. We don’t recommend exploring these areas unless you are familiar with the necessary safety precautions. Otherwise, call your a/c service tech.

  9. 10) Fan set at “ON” and condenser not functional - When the fan setting at the thermostat is set at “ON,” the blower rans continuously, even if the condenser is not functional. This may make you think the system is not cooling properly when, actually, it is not cooling at all. Check your fan setting. If it is at “ON,” set it to “AUTO,” which will make the fan run only when the system is functional. Wait a few minutes. If nothing happens, or it turns on but does not cool, see our blog post “My air conditioner won’t turn on. What’s wrong?”, or call an a/c service tech.

    An annual maintenance service at a minimum or, as recommended by most HVAC contractors, every six months will catch minor problems before they get out of hand. We recommend it.

While we hope you find this series of articles about home inspection helpful, they should not be considered an alternative to an actual home inspection by a local inspector. Also, construction standards vary in different parts of the country and it is possible that important issues related to your area may not be covered here.
© McGarry and Madsen Inspection


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More blog posts about heating and air conditioning:

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

  2. How can I find out the age of my air conditioner or furnace?

  3. The coils on my heat pump are covered with ice on cold mornings. What’s wrong with it?

  4. When does the ban on R-22 air conditioning refrigerant take effect?

  5. What color should the flame be in a natural gas furnace?

  6. What is the SEER of my old air conditioner?

  7. What is the difference between the “ON” and “AUTO” settings on my thermostat?

  8. What is a “ton” of air conditioning?

  9. How can checking the fireplace damper reduce energy bills year-round?

  10. What is the best air conditioner for a mobile home?

  11. How do I find the right size air conditioner for my house?

  12. What is an HVAC system?

  13. What is the difference between the SEER and EER of an air conditioner?

  14. What does an ultraviolet air treatment system do?

  15. The coolant line to the outside unit of my air conditioner is frozen. What's wrong?

  16. What size air conditioner is right for my mobile home?

  17. What is the minimum SEER rating for a new air conditioner?

  18. What does the “AFUE” rating of a furnace mean?

  19. How much life is left in that air conditioner?

  20. Why is there mold around the air conditioning ducts?

  21. What is a geothermal heat pump?

  22. What is the difference between a heat pump and a cooling air conditioner?

  23. Is it alright to close the air conditioning vents in unused rooms?

  24. What is the right MERV number for my air conditioning filter?

  25. Should I move my air conditioner into the attic?

  26. What are the minimum requirements for bathroom ventilation?

  27. What is an air conditioning heat recovery system?

  28. When should I switch the thermostat to “EMERGENCY HEAT” for my heat pump air conditioner?

  29. Why does the air conditioner condensate drain line need a trap in it?

  30. What is the average lifespan of an air conditioner?

  31. Should I remove an old whole house fan or keep it?

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

  33. Is it acceptable for an air conditioning condensate drain line to terminate under the house?

  34. How much will I save on my utility bill if I get a new higher SEER air conditioner?

  35. Will closing doors reduce my heating and cooling costs?

  36. Why is there a wall switch next to the furnace or indoor unit of the air conditioner in the garage?

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

  38. Which one is better for a home heating system: electric or natural gas?

  39. Why does an air conditioner condenser need to be level?

  40. How can I tell if an air conditioner uses R-22 or R-410A refrigerant?

  41. What is a return air plenum for a furnace or air conditioning system?

  42. When is an auxiliary drain pan required under an air conditioner indoor unit (air handler)?

  43. Why does it take so long to cool a house when the air conditioner has been off for a while?

  44. What are the right words to use when talking about a heating and air conditioning system?

  45. What is a ductless mini-split air conditioner?

  46. What is a FanRecycler and AirCycler?

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