Q. What does an HVAC inspection entail?
A. HVAC stands for heating, ventilation and air conditioning, all of which are part of the residential HVAC inspection. Inspecting the heating and air-conditioning portion of those systems usually starts at the thermostat. In some cases the inspector can determine whether it is a standard thermostat that controls the heat or air conditioning, or if it’s a heat pump system that may have an emergency backup system control. The only way to really confirm this is by looking inside the condensing unit outside to see whether a reversing valve — the integral part of a heat pump system — is present. At the beginning of inspecting both air handler (furnace indoors) and or condenser (outdoors), the inspector will note the size of both units and determine as closely as possible the ages of both.
Back at the thermostat, the inspector turns the blower to the “on” position, which will begin to circulate the air throughout the home. This allows the inspector to check for air distribution in each room without having to go back and forth. Be aware that certain outdoor temperatures can limit both heating and air conditioning system inspections.
If the outdoor ambient temperature is 65 degrees Fahrenheit (18 degrees Celsius) or cooler, then it is not recommended to test an air conditioning condenser (outdoor unit), as it could possibly damage the compressor. If outdoor temperatures are warmer than that, then the inspector will run the air conditioning system for an acceptable amount of time and check the temperature differential check. For a temperature differential check, the inspector uses two thermometers — one in the supply register and one in the return air register — as close to the air handler as possible to get the most accurate reading. The differences in temperature should be between 14 and 22 degrees. That being the case, the inspector will report that the system is running within industry standards.
If conditions allow that both the heating and cooling systems can be inspected during the course of the inspection, and if the cooling system is inspected first or vice versa, then the entire system should be shut down for a rest period in order for the system and thermostat to balance out before testing the opposing function. After this period, the furnace can be turned on and visually inspected. During a gas furnace inspection, the inspector observes the flame pattern of the burners, checks the operation and cleanliness of the system, and documents any abnormalities or problems. The inspector also should use a combustible gas detector to check for gas leaks, and, when the drafting system allows, check for the presence of carbon monoxide with the same tool.
The inspector will check any furnace filters for cleanliness and recommend cleaning or replacing if necessary.
Finally, the inspector will check air distribution for adequacy in each room by checking the air flow from the supply ducts. A simple test the home owner could perform is to place a tissue over the return air duct. If the system is supplying adequate air movement, there should be enough draw of air on the return duct to hold the tissue in place.
Keep in mind that the larger the house, the larger the HVAC system will be. In some cases, and depending on the size of the house, more than one system may be present. For example, a two-story home may be designed with a complete system for each level to keep the upstairs of a house as cool as the lower level. The more HVAC systems a house has, the longer the inspection will take.