AC Splits Yea or Nay

Do you take AC splits as part of your inspection protocol?



Dale do you bring an AC guy?:slight_smile:

How do you take a split? :shock:

Simply obtain a temperature reading of the return register and the supply register. You want to see a 12 to 15 degree difference.

Hi Brian,

No, every technician which has either serviced mine or customers has said it really has no bearing on how the equipment might really be functioning unless a temp reading is taken at the unit, and I have never seen a technician even take a reading from a register.

I do check the supply temp for readings in the 50’s which tells me it is operating correctly.

You know the way they build here, there could be ducts separated, uninsulated, or nobody has had the equipment serviced in years, which is generally the reason one is not producing the correct temps.

I have found the systems just designed poorly, under sized, two story homes with 12 foot ceilings with both returns on the second floor, the second floor very cool and you cannot bring the temp down normally on the first because of the design.

As a matter of fact, an entire subdivision is suing a builder here in Chandler for that very reason…wrong conditioning design of every home.

So a temperature split of 14-22 degrees makes no difference if the equipment is producing 65 degree air and returning 80 something degrees, it’s just not working or designed right.

If you are using a thermometer to take your split, it is worthless.

Dale interesting, so if it is 115 F outside you look for 50’s F? Seems like the unit would be working prettty hard.

There are so many reasons why this method DOES NOT do what so many inspectors think it does I can’t even begin to list them. There are literally a hundred variables that come into play. Like David said, if you are taking a dry bulb temperature you are wasting your time trying to determine if the system is working properly. I know this is what a lot of the HI books out there all say is the method for checking an HVAC , but it is just plain wrong.

Doug even more interesting. I am in the temp split camp, as that is how I was taught, and that was a question on the NHIE. I was taught that if he splits are not correct (taken at the inlet and outlet of the unit) then the system should be evaluated by a HVAC technician.

As a generalist HI I am all ears if there is a better way to test the AC. But if it involves specialized equipment, psychometric charts, and/or engineering, I will pass.

I take them across the coil and look for 14 to 22 degrees. It gives an indication of how the system is working. In and of itself, it is not an accurate measurement, but it can be used with other visual clues to give the inspector a better idea about the condition of the system.

I was only kidding. Should have used a different smiley.

Like others said…to many variables.

The only way to really test them is with gauges and instruments like the techs use.

If it’s 115 outside and the unit is producing 62 degree air from a duct system numerous feet long in a attic 155 degrees, chances are it’s doing the best it can.

Very seldom have I run across anyone who said the system was serviced in the last 12 months like the manufacturers recommend…so I naturally recommend it before the close of escrow, if the buyers disregard my advice…oh well…:shock:

I have seen many say that splits are worthless but no explanation of the position.


For what it’s worth, I also take the temps at several registers (clients like to see the data relative to the other rooms). If it takes me only 3 minutes to do - and the clients like to play with the laser thermometer, then so be it.


Ask any HVAC tech…they shake their heads like you asked them to wash your truck…:smiley: …You have AC in your home?..was it serviced this year?..:smiley:

There are to many things which could be wrong or right…:shock:

No AC in this 100 year old stone farmhouse, Dale. No need.

I understand that people have that reaction, but no one ever explains it. I can see if it is your sole evaluating criteria, but as an additional bit of info to form a whole picture…what does it hurt?

What it hurts is too many inspectors (old and new) are advising clients to have the unit serviced when there is nothing wrong with. Just got a phone call from a fella here that is HVAC tech and instructor and he wanted to tell me about a local HI (one of the high rollers) who recommended a two years old heat pump “needed a charge” based solely on the figure he got from doing a split temp profile. He got a temp difference of 15.4 degrees and decided it needed some Freon. First off if he got that much difference, based on what I am hearing in here than that system was working fine. Second, he was not only diagnosing the perceived problem but also making recommendations on how to fix it. If you call for a technician and they aren’t honest than you can get into some real money. The average HVAC service call fee is between 75-85 an hour. The same people in here that say they do a system analysis using this method also say they would ever exceed or go beyond the SOP. Well, which is it? You can keep doing whatever you want to. Its your company and your business. How many of you are standing in front of the return air grill with your handy infrared while reading the figure. Did you know just by you standing in front of the grill you can and probably are raising the temperature you are reading? And how far are you from the supply registers in the ceilings. The further you are away the less reliable the figures. The circulating fan also generates a fair amount of heat that is figured into the formula when doing a system capacity check. What about the indoor humidity? Do you check that? Real important as it can represent up 20% of the heat in the home. It is called latent heat. It makes a huge difference. What condition is the evap coil in? If it is nasty and clogged that will definately affect the performance and life of the equipment. I recommend taking a course. You will be amazed at how much you thought you knew and were mistaken. Like I said, you can keep doing it any way you want to.

I have asked numerous techs why, they said it is folklore. That is why they have hundreds or thousands of dollars worth of testing equipment to determine exactly how the equipment is operating.

If there is still unacceptable air coming from a register, other issues are present.

Here in the desert it is usually the design of the system causing problems. Refrigerant lines running 60 feet to an Air Handler in an attic 155 degrees…:shock: …with flex ducts throughout the attic making long runs to the rooms…](*,)

Yeah, Dale, I figure when you live about 15 inches from the sun, you might experience some issues with the AC.

As for the other issues - I appreciate someone taking the time to list them.

Regarding the SOP - I exceed them. I am not embarrassed to say so. I think they are a bare minimum and I was disgusted as a homebuyer at my own HI who only stuck to the SOP. That was one reason I knew I would succeed in this business.

As for the HVAC issues - I think maybe the case regarding splits is overstated. I don’t think many (if any) are basing their entire evaluation of the system on this information, but it is a valid measurement of two elements of the system that can provide some insight into the overall operating condition of the unit.

If the register is blowing at 54 degrees and I am three feet away, do you think my client cares whether my readings are off by a fraction of the overall percent due to body heat? No. they think it is cool and they like kowing that they are getting cold air on demand.

Now if I measure 68 degrees at that register - we have a problem.

It is like everything else in HI - many times you have to see the whole, not the individual parts. But small indicators are all clues that there may be a more significant item lurking.

I gues if I ever get time I might take an HVAC course. But then again, if I have the measurement equipment, and I can take ambient humidity readings, and take apart and evaluate an HVAC system - I am now an HVAC professional. I think I’ll just review the system and refer it out to those guys so they can do all of that…