How to Tell if a Ductless AC is Working

Bryan goes through his Mitsubishi MXZ system’s specifications to find the CFM (volume of air moved per minute). The CFM stays the same across the different sizes, so it would appear as though much of the increased capacity comes from latent heat removal.

After syncing up the 410i, Bryan uses it to take a traverse reading and measure his baseline. He took the measurement in two different pieces. He also configures everything in the Testo app to tailor the readings to the unit. His traverse reading determined that the ductless system was putting out 305 CFM, which was in the appropriate range according to the manufacturer’s specs.

Then, Bryan uses the 605i probes in the supply and return to measure the cooling capacity. He measures both airstreams with the setpoint at 65 degrees. In the app, he configures the CFM based on a wet coil (according to the specs). Bryan determined that the system ran about 7,000 BTUs, but the BTUs jumped up to over 8,000 as Bryan reduced the setpoint temperature even more (from 65 to 61 degrees).

We recommend using these tests when commissioning ductless systems, as you can see how many BTUs the system is actually moving.