The case comes with two 605i instruments. Make sure both probes are open, and then you can put one probe in the return and the other in the supply duct. Once you’ve done that, you can set in your airflow (such as by using the 405i hot wire anemometer to get an in-duct measurement; measure at a point of low turbulence and do a full traverse test). You can configure your measurement by selecting the gear at the bottom and choosing “configure measurement.” Manual configuration is also possible.

On the 24,000-BTU system we tested, we determined that the delivered capacity was around 23,400 BTUs with a 55.4-degree supply air temperature and 76-degree return air temperature. Telling the customers a bit about the delivered capacity in BTUs allows you to show them that you’re giving them exactly what they paid for.

Testo: https://www.testo.com/en/