So really there is never a time where “apparent Delta T” is employed other than perhaps in the mind of the inspector as he is viewing an image live. For reporting purposes using a qualitative approach, the only Delta T which is acceptable is an exact one. Correct?
Is there ever any application for an apparent Delta T?
During my Infraspection courses, qualitative and quantitative inspections are discussed and I’ve read a bit about apparent delta T and actual delta T, but the lines seem blurred a little when applying these different concepts.
Are qualitative inspections of little value in the market since they don’t involve any measurements? And how is apparent delta T used or better yet, why bring it up if it is of no use?
I guess I’m trying to understand the application of all this and see how it would be used in my business.
My prior posts are not opinions or statements of fact, they are questions and attempts at gaining some clarity.
When you have five different material types within a panel most of which you cannot touch, or determine actual emissivity, some of which have varying geometries (e.g., the cavities of the hex socket on the main terminal lugs), have varying oxidation levels and varying surface angles to the sensor, all of which affect emissivity. Exactly what do you set your emissivity values to for this type of situation???
Unless you are examining specific components and you can reliably determine the real emissivity values of those components, you can’t determine a single, specific emissivity value because each object in the panel may be different (i.e., the ε value for the molded case breaker body doesn’t equal the ε of the terminal which doesn’t equal the ε of the conductor which doesn’t equal the ε of the insulation and the ε of the shiny new terminal doesn’t equal the ε of the older oxidized terminal and the ε of the cavity of the main lug doesn’t equal the doesn’t equal the ε of the rounded outside of the terminal head…)
Most prioritization scales, e.g, NETA are conservative because of this.
I reserve the quantitative work for those things that demand it and for which I can reasonably determine or alter the ε values to a known ε. If I can get a piece of a failed component (last Friday I was able to pull a piece of the covering from a failed sectionalizer), then I will use that to determine the true ε value. None of this is practical or necessary when shooting a homeowner’s electrical panel. Try to identify and focus on high ε value targets and always, when possible, compare similar components under similar load rather than ambient. For instance: If you compare the insulation (because the conductor insulation has a high ε value) temps of two similar conductors carrying similar loads, or better yet two locations on the same conductor (because you know the load is identical), you are not likely to be far enough off to make any difference in the NETA priority classification. Make sure that you know your imager’s spot size ratio and that you are close enough to your target (especially small cylindrical targets like conductors) to get an accurate measurement or it won’t matter what else you do because your reading will be off.
Performing thermography inspections is not rocket science, but it’s not a casual point and shoot proposition either.
There may be a time when you may want a temperature measurement in your report and you have no idea what the emissivity of it is. This would be an instance when an incorrect Delta T would not pose injury or catastrophic failure to occur. In these cases it could be acceptable to set your camera emissivity to 1.0 (the camera calculation program uses this emissivity such as T Reflect) and take the scans referencing that the temps are “Apparent Temps at 1.0 E”.
An example may be on water intrusion. Air and water look similar (often because both are present). We know the wet bulb temp of the air and may want to show/know it is outside this range and is likely associated with air (ie. not a plumbing leak). No one is going to die and if it’s not water when you open the ceiling, you need to fix the air infiltration issue anyway…
If your calling a breaker hot in reference to the panel ambient (unloaded similar component), you need to do your homework.
If you have a 7F Delta T using a circuit breaker emissivity of .95, you will have a 39F Delta T if the camera is set at the emissivity of a copper conductor.
If you don’t know the emissivity, err to a lower E.
It’s better to over react than to get someone killed.
How have HVAC and Electrical Specialist been measuring with an
infrared thermometer for so long and not an IR camera? Are all of
them wrong and cannot diagnose anything?
Read Mr Evans post. It explains with sound reason the folly of
thinking you can get “exact” measurements out in the field, when it
is not needed anyway. A certain tolerance is allowed for their
purposes out in the field.
You claim all HAVC and Electrical Specialist are wrong and
cannot diagnose anything, while making the false claim that you
know the exact emissivity of all materials in the field and your
readings are an exact science. I am not sure which one of these
positions is a greater exaggerations. Is Mr Evans wrong also?
You cannot back up your claims.
It’s time to do the moon walk and save face, while backing
away from your position.
I rest my case. When you say all the HVAC and Electrical Specialist
in the world are all wrong and cannot diagnose anything, you are out of
touch with reality. The schools that teach them must be wrong as well.
Their track record of diagnosing and repairs must be an illusion also.
**I didn’t say “couldn’t diagnose anything” you did.
Their "Apparent Temperature Delta T is not a “Corrected Temperature Result” if they have no way of correcting it.
I have used an IR Thermometer in HVAC since 1981. I have one in my tool belt today.
I know exactly what and how they were / and are used.
As usual your are twisting the subject, injecting misinformation and basically are showing exactly what you don’t know anything about.
You were done before you got started.
What reasoning should we be using when you come in with a thermometer application when the rest of us are discussing thermal imaging equipment?
By the way, my IR Thermometer has emissivity adjustment. Does yours?
Your implying all the HVAC and electrical contractors do no, so I assume yours does not as well.
Do you diagnose electrical / mechanical with your IR Thermometer and use the thermography standards as a basis for your corrective recommendation? How could you use these standards when your not using the proper equipment or procedure to determine the equipment conditions in the first place?
I ask you
**Are all of them wrong and cannot diagnose anything?
and you said Yes they have been “wrong” all this time,
All of us already knew you were wrong, but we finally got you to admit it.
Temperature readings can be done even with an infrared thermometer
and as Mr Evans pointed out… the exact emissivity of materials cannot
be known because there are too many variables in the field. It is not
needed anyway because we don’t need exact lab results to diagnose
something for a home inspection.
If an IR thermometer can work for HVAC and Electrical Specialist all over
the world, then an IR camera will work just fine, even if we don’t know
the emissivity exactly. Get the point? You have to stop pretending to know
things that are exact, when it is not possible in the field to do so… and it is
not required to produce lab results for a home inspections.
No… the question is this… If HVAC and Electrical Specialist around the world can diagnose and repair items in the field with an IR thermometer, then it cannot be that difficult to measure a temperature, for home inspection purposes, with an IR camera. You started out saying only exact numbers were allowed, but have since back tracked to allow for the fact that the exact emissivity of things cannot be known because there are so many variables. Please read Mr Evans post so you can see the common sense approach that will ensure you avoid errors of 32 degrees. It is not that mystical to understand. You assume all of us are doing it wrong (just like you said about the HVAC and Electrical people of the world). It does not take a Level III certification to do an IR home inspection.
Please tell me what I am doing wrong. Be specific and offer proof. You seem bold in your statements to accuse me so the burden of proof is upon you.
If Mr Evans gets it and explains it with such ease, why is this such a hard issue for you to grasp? I fail to see how you advance your position by saying the whole world is wrong but you. What are all of us doing that is so wrong? Are all of us missing things by 32 degrees in your opinion? Your statements seem extreme.