Hot Attic Ventilator

[Peter W. Bennett]

How hot is too hot?

[David A. Andersen]

Call the manufacturer.

If you want to know about the motor in the field, you should be taking the amperage draw and compairing it with the name plate data...

Thermal Imaging is not the "answer all" tool!

First of all you have to correct the apparent temperatures in the scan.

Then you have to get the information on the component you are scanning.

In every case, thermal imaging will be supported by another form of testing which you must be qualified in doing or you should not be using thermal imaging for that application as you are not properly qualified.
　
If you elect not to take amperage ratings on this motor because it is beyond your SOP, then you must be willing to hire an electrician to do that work and include it in your inspection fee to start with.
　
If you are going to defer this additional testing to an outside source, you must be ready to pay for the services if you are not correct in your assessment.

[David A. Andersen]

As a learning experience, let's discuss the emissivity settings for this scan.

What do you expect them to be?

What are we measuring?
A bearing or electrical wiring.

What is the surface of the component we are measuring?
Does it have oil on it?
Are we measuring the copper conductor or the insulation on the copper conductor?

Is the bearing a direct or indirect measurement?

What effect on emissivity does geometry play in this scan?

What affects does being out of focus have on this particular scan?

Is adjusting for temperature reflect an important issue in obtaining a corrected temperature in this case?
　
What is the correct emissivity setting? ___________

[Peter W. Bennett]

Thanks David for your detailed Level III reply.
Since my observation was a qualitative one, I was interested in a qualitative answer, i.e. the friggin thing is burning up!
Have you ever scanned one that was no big deal, and another which was alarming?
Thanks,
Peter

[David A. Andersen]

Well actually because you're relying on the numbers it is not qualitative.

You cannot determine a "this is too hot" with a qualitative analysis. 1° temperature rise can look like a forest fire!

If there are any numbers on your scan, you are relying upon them to make a comparison with something else.
You cannot compare two "apparent temperatures" to one another. In this case, your box measurement tool is comparing ambient air with the highest motor winding temperatures.

To determine if it's too hot, we must compare temperature rise to the ambient temperatures or temperature rise to a like component under the same load.

Take a stab at my second post questions.
It is not intended to degrade anyone.
It's to stimulate the thought process, conversation and understanding of thermal imaging.

The correct answer is extremely simple, but you must understand and go through the other steps to be sure you are correct before potentially inflicting monetary loss upon someone else.
　

[Chuck Evans]

Here are some links to additional tips for making assessments of motors:

http://irinfo.org/tip_of_week_2010.html#t05062010
http://irinfo.org/tip_of_week_2007.html#t02192007
http://irinfo.org/tip_of_week_2004.html#t08102004

This all gets pretty involved for a home inspection add-on service. My advice is keep your imager out of the attic when doing home inspections and save motor inspections for commercial jobs (at least that's what I do).