Test in-Test out

When I started in the HVAC industry, I was taught a method of testing that has served me well for several years. It’s called “Test in-Test out”.

What exactly is Test in-Test out? When diagnosing an issue with the equipment, many times we make changes and head on to the next job. How do we know
if the changes we made actually made a difference? Use the procedure of Test in-Test out. When you originally diagnosed the equipment you had a certain set of readings (pressure, voltage, etc.). Once you perform the needed changes, retest everything and compare your readings. Did anything change? If not, then the problem may not be completely resolved.

Here’s an example: If you check a pressure switch because it is not closing, you may find out that the inducer is only pulling .3”
wc, and the switch needs .9” wc to close. You look
deeper into the system and realize that there is a dip in the exhaust pipe that is collecting water. Once the repairs are made and the system is back in operation, retest to verify that the repairs you made have significantly changed your readings.

Using this procedure will give you and your client peace of mind that you did everything to resolve their issue.

Jeff Rosenblum
Technical Support
17 Years Industry Experience
Cell (330) 962-2491
jrosenblum@famous-supply.com

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