[Alumifab]

I am looking over my inspection report and need your advice on 2 things.

In layman terms what does this mean, other than it's not working efficiently.

These 2 items are from my inspection report.

1) "Temperature readings: The target range or spread that I use is between 16° and 24° between the air return and the air supply registers. Some inspectors may use another range. Using an infrared thermometer to measure the temperature at the air registers is not technically a diagnostic analysis, however it's the most commonly accepted procedure in the home inspection industry.

Air Temperature Differentials (HVAC Cooling System) (outside temp during inspection was at 60 degrees)
Return 71 F°
Supply 42 F°
Differential 29 F°


2) Air Supply Register Differentials 10° (HVAC Cooling System)
"Some of the air supply duct was leaking air where it is attached to the indoor air handler plenum and at other connections or transition points.
Some of the air duct was not properly supported in the attic and had more than one half of an inch of sag in it’s runs. Some of it was kinked or constricted. Constricted air can decrease comfort and increase system operating costs."

I am going around the plenum and using mastic where I see leaks and opportunities to seal.

Your thoughts and ideas are appreciated.

 

[user_12345a]

Air Temperature Differentials (HVAC Cooling System) (outside temp during inspection was at 60 degrees)
Return 71 F°
Supply 42 F°
Differential 29 F°

Testing at 60 degrees and low indoor humidity will yield a different differential than when the system is actually being used.

The differential alone doesn't really tell you what's happening; there are too many variables.

In your case, the test result is: "its cooling". Whether its getting proper airflow or the refrigerant charge is right, who knows. For example you could have scenario in which there's a 20 degree differential, passes this crude "inspection" but is in reality not properly charged -> low airflow can hide that. Could also have the opposite scenario where the machine is cooling great but the airflow is very far in excess of what's needed, but that's probably extremely rare.

There are more valid diy-friendly tests than what the inspector did.

 

[Alumifab]

Let me know of any friendly tests and I'll try them.
Here in Dallas we have 2 more months of 'winter', if you can call it that, haha.
When it gets warmer outside and I start using the AC we shall see if it works correctly....
I have a friend who will let me borrow his smoke pen to see leaks more effectively in the hvac unit.

 

[user_12345a]

With a clean condenser coil you can estimate how much heat the unit is removing based on the outdoor differential if you can locate the model number, look up the cfm.

1.08 x cfm x delta-t - (estimated wattage* x 3.412)

*or with electrical knowledge if comfortable, you can measure compressor amp draw and calculate power use. The energy consumed by the compressor gets absorbed by the refrigerant and rejected by the coil.

Can also do a test which takes indoor humidity into account; uses wetbulb return air temperature, chart tells you what the supply air temp should be. Significantly higher supply air temp indicates low airflow and lower indicates a capacity problem or excess airflow. Excess airflow reduces dehumidification but may be great for capacity/efficiency. Do not expect airflow to be correct, it most likely isn't unless the ducts were properly sized and the system actually set up correctly.

Uses bottom portion of the charts on this page: http://efficientcomfort.net/Charts.html