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Why Is The Air Conditioner Not Cooling Properly?

All home inspectors have a method they use to inspect the air conditioning system. We know the obvious things to look for and how to energize the system and see if it appears to operate properly. A visual home inspection is limited to the time we are at the house. I try to leave the system running as long as practical, however sometimes it is a shorter period than I would like. We check for proper operation, thermostat response, leaks, noise from the compressor, fan, blower, and proper condensate discharge. If everything checks out ok and the system is running properly but there is no or very little cool air coming from the ducts there is an issue. Of course, we are going to recommend a qualified HVAC professional evaluate the system. There are some conditions that may cause what appears to be a operating system from producing adequate cold air and proper dehumidification. A normal temperature drop should be between 14-24 ℉ (measured at the plenum about 12” from the supply & return side). Another issue may be the length of the refrigerant lines. Normally 60’of horizontal run and 45’ of vertical distance is the maximum recommended by many manufactures. Anything longer than that may cause proper operation issues. The refrigerant lines should be supported approximately every 8’ and supports should be compatible with copper as not to corrode. Home inspectors are not required or even expected to diagnose a problem or conduct a temperature drop analysis; however here are some conditions that may cause a central electric air conditioning system to not adequately cool that they should be aware of;

  • Evaporator coils located before the fan
  • Evaporator coil not rated the same BTU as the condenser unit
  • Improperly sized system
  • Condenser unit outside has improper clearance or dirty (recommend 3’)
  • Growth / bushes / landscaping to close to the condensing unit (recommend 3’)
  • Condenser unit to close to dryer discharge (recommend 3’)
  • Condenser unit exposed to direct sunlight throughout the day
  • Condenser fins are damaged
  • Insulation missing on suction line
  • Refrigerant lines kinked or damaged
  • Dirty evaporator coil
  • Dirty air filter
  • Low coolant
  • Undersized or restricted cold air return
  • Leaks in the duct system
  • Insufficient supply / return ducts (often seen in Cape Cod style houses)
  • Ducts not properly balanced. They should be changed in the winter / summer months if the system in integrated with heat
  • Improper fan speed (we see this with older retro-fitted AC systems)

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