Testo 435-2

[Gary Reecher]

About a month ago I got the Testo 435-2. Here are some photos of the testers screen. Just a few of the things that the Testo 435-2 can do: measures and calculates dry bulb, wet bulb, dew point, RH%, FPM, CFM. Takes this information then calculates the cooling or heating displaying in a chosen format of BTU/HR, Ton or Kilowatt. The meter uses a vane anemometer for measuring airflow. Programming the area of the ductwork can be done in square inches, or you can input the width and then height if measuring a rectangular duct or you can choose circle and input the diameter. The meter will then take this information and calculates the CFM airflow using the measured FPM. Temperature input is from 2 wireless thermometers using RH probes, one in the return and one in the supply. Make sure if there is a bypass humidifier that the bypass is blocked off during testing. You can also use a standard K thermocouple probe. However when using the K thermocouple probe the meter will not calculate the BTU/HR. Timed measurements can be made which will average the readings when traversing the duct work. When the timed measurement is ended the meter then calculates the average of all the readings that it measured. There is more that the meter can do but just calculating average CFM is great. Calculating the btu/hr is icing on the cake. If this meter can take the day to day use and come out ticking like a Timex watch after John Cameron Swayze took it off that outboard motor propeller, oops really showing my age, it is one tester that is long overdo to simplify airflow measurement and calculating system performance. Have an infrared printer? Well you can print out the measurements at the job site or you can download the measurements to a computer. This is something that I have yet to do. These are measurements taken off my home unit a 1995 Trane XL1400 1-1/2 ton heat pump duel fueled to a Trane XV90 variable speed blower gas furnace.

Display of BTU/HR on line 1 and CFM on line 2
or you can have it displayed as


you can use an infrared printer and print out the test results.


The kit runs about $1,500. Since it calculates btus it could check the btus for heating which I have not tried yet.