Do you measure Delta T?

I did an inspection the other day where the client was a HVAC guy, and he insisted on checking the temperature differential, but I didn’t have a thermometer…so he grabbed his. My question is, how many of you actually test the temp change across the coils? I know it’s not required, but I kinda feel like it would be a good service (that’s easy) to provide my clients. Should I get myself a probe thermometer? What are your thoughts?

Test out the “Search Function” on this site.
Search: “Temperature Splits”

Then decide how you will protect yourself when your “simple service” fails to perform as expected.

See this recent topic on AC splits …

Just because an air conditioner is producing cool or warm air really only means its producing cool or warm air, nothing more, nothing less.

I have a habit of asking homeowners when the unit(s) were Serviced last; you usually get that deer-headlight look from them, their the same group of people who wait until their car engine fails before dragging it to a mechanic to have a new engine installed.

Their the same idiots using the allergen filters that haven’t been changed in a couple years, if ever.

People seem to fail to realize this equipment needs to be Serviced yearly, not when it breaks.

Regardless of what the conditioning system is doing at the time of the inspection I strongly recommend a licensed contractor Service the unit at the owners expense before their inspection contingency period ends if he/she cannot produce a receipt it was in fact serviced in the last 11-12 months.

If it has, which is RARE, 9 out of 10 times it due for Service again.

I have three Trustworthy A/C Men I know personally, the type who Service the equipment, not the type who are paid based on sale commissions during the Service call.

I highly recommend everyone find a good A/C man who doesn’t rip off the public, the kind of guy who tells your client the allergen filter is probably the worse thing you could ever stick in a return register.

These guys are hard to find, but their out there, once you find a couple of honest HVAC men recommend them to your clients, they’ll thank you for the advise, and everyone is happy.

Thanks guys…I think I’ll leave this one to the pros.


Remember if you are going to get a meaningful delta T across the coil you need to get the wet bulb temperature of the return air. Few home inspectors have the equipment to get the wet bulb.

respermo, has the one and “only” answer.

You can not determine psychrometrics without one more thing beyond the dry-bulb thermometer reading…

respermo makes a great point. The more technically exhaustive and complicated you get, the more trouble you can get yourself into, without corresponding benefits to your client.

My pre-inspection agreement already states the inspection is not technically exhaustive. If the weather is warm enough to run the unit, I just run the blower fan to get a base line temperature reading with a simple thermometer at a register after the temperature stabilizes, and after that, put the fan setting beck to “auto,” turn down the thermostat, and read how the air is cooled.

That’s what interests my clients, anyway, and I’ve found it easy enough for them to understand that the weather conditions and initial temperature on a given day obviously affect the readings.

If requested I will use my flow meter and temp probe but only if insisted by my client. Generally this is because they have heard something from a AC or HVAC specialist. I always put in my report if I could not test the AC because of the temperature outside and recommend it get tested when it is warm enough.

Care to rephrase that statement before you get your chit jumped again?!! :wink:


CMI lingo. :o

OMG someone is going to wake the Tenn sleeping bear;-);-):wink:

Which reads in part when translated:

· The air conditioning system could not be tested as the outdoor temperature was below 60 degrees F.

He must be reading a new IR book.:p:p

Mr Currins:

The air conditioning system could not be tested as the outdoor temperature was below 60 degrees F.

This is not even a correct statement according to new info a compressor should not be operated below 65 F. You can test below 65 F but I will not.
Just because it is in the SOP does not mean you are protected if you damage the compressor.
FYI all my reports have the Temperature during inspection.

Here we go again…

According to “who”, and wheres the documentation???

One manufacturer **does not **dictate a change in industry standards.

OMG it was 35 degrees outside ambient this morning and I fired off the A/C unit the A/C police must be looking for me by now. SHHHHHH don’t tell anyone

You mean it is actually colder then we are. Are temperature is 3 degrees Celsius or in US language 38 Fahrenheit.