Heating Differential

I document the air temperature rise from the furnace data plate and put this information in my inspection report. Today I had a 2017 Carrier furnace with a 30-60 degree air temperature rise listed on the data plate. My temperature measurements directly at the plenum were 150 supply and 80 return which put me outside of this range with 70 degrees. I know most inspectors just take a picture of the combustion burners. Does anyone else take these measurements? If so, do these measurements warrant further review by a professional? Thanks.

I do not take these measurements. Very far outside our SOP in my opinion but your state may require more from you.

So your rise was 10 degrees higher than the data plate. Is that 30-60 degree rise listed meant to be used as measured reference point? Or, is it a description of the typical output for this system?

Basically, my question is this: Is that rise range the actual performance data points to be used for evaluating the efficiency of this system as prescribed by the manufacturer?

How does the manufacturer recommend you measure rise?

Once you have those answers then you can decide if it is in need of service because the manufacturer will tell you what to do if readings are out of range.

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Taking a picture of the combustion burners is not the same as evaluating the combustion burners. Do most inspectors just take a photo? What would that illustrate?

I see where inspectors take a picture of the combustion burners in operation to show the furnace is functioning. I personally like to take a picture of my SPK2 thermometers at the supply and return plenums and show the differential and compare it with the air temperature rise range listed on the data label inside the cabinet. As inspectors we need to cover our rear ends in some way. How do you visually prove in your reports that the furnace is functioning? It would be nice to check off the inspected box only, but what happens if the furnace doesn’t work when the client moves in?

I don’t prove anything, honestly. My word is my word.

But I agree with you about covering your butt. I do take a photo of things and keep them for myself as CYA photos.

If my client says something is not working after they move in, then we have a conversation. I tell them I performed a multi point evaluation on that component and only after that will I check “inspected”.

Then, I will remind them conditions can change once I leave the home. Sellers will do things or coincidently something will break. And then remind them again of my professional evaluation and serious protocol before I will check off “inspected”.

I do not get defensive. In the end, if I must share a photo I will, but I will only do it after I remind them I am a professional certified inspector with significant qualifications and experience.


Stay within the SOP. You don’t have to prove anything.

Keep pictures of recorded temps but simply indicate in your report that the heating/cooling equipment was functional from normal controls. If it doesn’t work and there isn’t an obvious breaker or switch in the off position, note it and move on.