Temperature Splits

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1

Originally Posted By: phinsperger
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bwiley wrote:
I use temp split only as an indication of the unit's performance. I never put my gauges on them, as it is not my equipment.


I also measure split to give myself a very very general idea of the efficecny. I have not been puting this info in my reports.

Where do you take readings? As close to bottom of plemum as possible, middle, or top?

What equipment (thermometer) do you use? Probe, Magnetic, non-contact infared? If you use a non-contact infared on galvanized sheetmetal, do you apply making tape, magentic sheet or something else to prevent emissivity problems?

What is the min split you find acceptable? For what weather condtions? For what type of furnace, etc.

--
.


Paul Hinsperger
Hinsperger Inspection Services
Chairman - NACHI Awards Committee
Place your Award Nominations
here !
2

Originally Posted By: rsummers
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I use a sling Psychrometer to check wet-bulb and dry-bulb temps at the R/A. Then use a chart that I got from the California Energy Commission Title 24 Standards (page icon_cool.gif. With that chart you find the proper Supply air temp. The S/A temperature should be within 3 degrees of the target temperature or you may have a refrigerant charge or air flow issue. I take my supply temp at the air handler if I can if not I pick the closest Register to the unit. I use a digital thermometer to take does readings. The laser guns are not that accurate they cant measure the air temp.

3

Originally Posted By: pdacey
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I use a digital probe thermometer. It has a magnetic holder so you can stick it on the return air vent. I measure temp. of the return air at the vent and the supply air at the plenum. I look for a differential between 15 and 20 degrees. I report the two readings and the diference. Anything else would be beyond the scope.

–
Slainte!


Patrick Dacey
swi@satx.rr.com
TREC # 6636
www.southwestinspections.com
4

Originally Posted By: Blaine Wiley
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I use a digital probe thermometer. Almost all of our units down here use ductboard at the supply and return ends. I look for a 14 to 22 degree split. A unit properly sized for the home should be in that range with our normal outdoor temperatures.


I also cheat. My next door neighbor is an HVAC dude, and he comes with me during the slow times. Amazing what practical knowledge one can learn when picking brains the you don't get out of books or class.

5

Originally Posted By: nstone
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I use the digital probe also. If I can get to the air handler intake and exhaust side I’ll stick my probe icon_redface.gif in the plenum and wait for it to stabilize. Usually, there is already a hole made by the a/c guys so I use theirs to keep the plenum from looking like a piece of swiss cheese.


I also look for a temp differential between 14-22 degrees. It’s also a good idea to check the exhaust temp at all the vents in the home. This is quick and accurate enough with a laser thermometer. Found one the other day where all ducts read around 54 degrees but one read 72 degrees. On closer inspection of this duct in the attic it was half way disconnected allowing warmer attic air to mix with conditioned air. This is what I call a great find as when you report this to the buyer they are always thrilled!



Cheers,

Neal

--
"An Eagle's EYE means
a Better Buy"

6

Originally Posted By: pdacey
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bwiley wrote:
I look for a 14 to 22 degree split.

nstone wrote:
I also look for a temp differential between 14-22 degrees.


Why 14-22?

--
Slainte!

Patrick Dacey
swi@satx.rr.com
TREC # 6636
www.southwestinspections.com
7

Originally Posted By: jpeck
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When I check TD, I also look for a 14-22 degree split, however, because there are so many things which affect the TD, I rarely take it.


In most cases, the TD is meaningless for an HI to take it. I now, that contradicts what is taught in the HI schools, but using TD to determine condition is akin to finding out what the mpg of a used car is without knowing engine size, vehicle weight, load being carried, tire pressure, city or highway driving, whether it is uphill or downhill, etc. It means nothing without a lot more information.

--
Jerry Peck
South Florida

8

Originally Posted By: rsummers
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I know by reading posts on this board that I’m not the olny one that has been in the HVAC trade . There is no right temp to look for when determining the temp split on air conditioning equipment. It always depends on the OSA temp the R/A temp and the humidity levels in the home. I used to always look for a 20 degree temp difference while starting up the A/C but I wouldn’t keep adding freon to archive that temp if the super heat or sub- cool temp was wright. With out having the proper tools or experience to check the performance of air conditioning equipment I wouldn’t advise commenting on it.

9

Originally Posted By: nstone
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To Jerry, Roland:


Great, you provided information contrary to what I have learned and what is taught in the HI books. Then, how do you inspect HVAC??? Do you go way beyond a visual and remove panels and/or disconnect freon lines?
If so, I think you are asking for problems and potentially will break something, experienced or not.
I say, stay with what you've been taught and read as it is backed and written through experience. I have personally found further problems when I find an HVAC split outside of 14-22 degrees...in one case both the compressor and evap core were shot...in others, it was one or the other.
!4-22degrees(or 15-20 as written in some manuals) is well within the scope and legal rights of your profession. Removing fittings and panels on HVAC is not. In any case, you write it up recommending a licensed HVAC technician check the operating performance of the system.

Neal ![icon_wink.gif](upload://ssT9V5t45yjlgXqiFRXL04eXtqw.gif)

--
"An Eagle's EYE means
a Better Buy"

10

Originally Posted By: rsummers
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I never put my gauges on units or disconnect any thing. I do remove panels to view the electrical and amp the compressor and condenser fan. If there is something that needs addressed don’t diagnose the system only recommend that a professional be brought in .

11

Originally Posted By: phinsperger
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Posts from Texas, Florida and Calif. Being just a little more north I was more kind of wondering about heating splits.

–
.



Paul Hinsperger
Hinsperger Inspection Services
Chairman - NACHI Awards Committee
Place your Award Nominations
here !
12

Originally Posted By: Blaine Wiley
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Phil,


Don't you guys up there just check to see if anything warm at all is coming out of the ducts? I guess compared to outside in the winter, 30 degrees would be warm though. ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif) ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif)

13

Originally Posted By: jpeck
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I check the condition of the unit, make sure that all the panels fit properly, the unit is clean inside, the coil is clean inside, the condensate pan is not rusted out (if metal), the return air plenum is properly lined and sealed (if not a return air closet), the duct work fits on properly and is sealed (does not leak air), that the loops where the copper come out of the coil and goes back into the coil are all cold (warm loop ends near the top indicate a likely refrigerant problem), the coil is not iced up (part of being clean), etc. (there is more to it than that, but that gives the idea of some things to check).


Basically, yes, it is a "visual" inspection. Most air handlers do not make it that far, but if everything else falls into place where I expect it to be, then (and only then) do I sometimes even bother to take a TD.

More likely than not, there is so much wrong by then that I know a TD reading would give a false reading. I.e., a dirty or blocked coil or filter will restrict air flow, causing a false TD reading. Air leaking out of the panels also affects the TD.

ALL of the intended air must pass through the coil for proper heat transfer to the refrigerant, which is what the TD is checking for.

If you give the a/c a quick look see, notice a 'cleaned off' coil, check the TD and find it to be within range, you may have committed a mistake, because the coil is likely dirty and heavily restricted between the fins, and / or the fins are coated with crud, reducing the ability to transfer heat through the coil to the refrigerant.

I rarely feel a need to take a TD reading.

--
Jerry Peck
South Florida

14

Originally Posted By: kluce
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I like to put my gauges on the AC unit. Most times it only takes a few minutes. There are short cuts on determining if the unit is charged properly which only takes a minute or two and gets me in the + or - 3 PSI. Plus it tells me if there is a restriction in the line. One (I found out later) that the screen in the liquid line by the A coil was plugged with flakes. Enough to cool but not freeze. Who ever installed the AC unit didn’t braze properly. Plus I can tell if the valves are going bad. I have found this a couple of times. I don’t report exactly what I see but I do recommend having a heating tech. look at it further.


When it comes to temp drop. I don't do it. If there is warm or cold air coming from the registers, that's good enough for me. An HVAC tech. (around here) normally doesn't check that until after checking everything else. If the suction line starts freezing, it's most likely there is a restriction somewhere. If the furnace keeps going off from the limit, then I know there is a restriction on the newer furnaces and/or the limit control or blower is set incorrectly. Yesterday it was a restriction in the heating system. Somebody disconnected half of the heat runs and plugged up the holes.

Note: Took classes from Carrier and Reem many years ago. Both recommend taking temp. drop at the return drop and after the plenum. This location would vary depending on the setup. My thought is they want a good mixture of air from the whole house and good mixture of air from the A coil.

Things are different in different location. What's good for the goose is not always good for the gander.

15

Originally Posted By: Blaine Wiley
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Kevin,


That is far above what a visual inspection calls for. By your post and seeing that you've taken classes, I would assume that you also have a current CFC license. I doubt many of us carry those.

Since you know what you're doing, cool. But I would not recommend this for the average HI.

16

Originally Posted By: kluce
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I agree.

17

Originally Posted By: kluce
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But for anyone that is Fed. licensed to check with gauges. It does have it’s advantages if you want to do it. It still falls in as a visual inspection. Like checking outlets, or taking the panel off an electrical box to inspect wires.

18

Originally Posted By: Blaine Wiley
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You don’t have gauges for Puron, do you?

19

Originally Posted By: kluce
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Yes. When I worked for a company that sells Carrier. As far as I know, only Carrier/Bryant uses Puron for commonly installed AC units around here. My father-in-law has a 12 seer Carrier AC unit which uses Puron, he likes for me to clean and check his unit every spring.


From talking to the installers around here. It's common practice (during the winter) on new installs and replacement that they evacuate the system, add some freon (guessed from the length of the line set) checking for leaks for the last time, then letting the freon loose from the condensing unit. This is good enough so when home owner turns the unit on, it will cool the house. The only problem is that no one really knows if the unit is charged properly. Only if they call wanting it checked out will somebody come out again. That's what happened to my Father-in-law. I moved here two month later and when spring came around, I checked the unit and it was enough to cool the house but wasn't getting the efficiency.

If I find that the unit is low on freon, I always recommend further evaluation from an HVAC tech.

Story:

Once I found the AC unit was charged good enough but oil was where the line set connects to the condenser. I had a feeling that they had somebody charged the AC unit but didn't want the leak fixed. A little spit on where the oil was coming from showed the leak. Unit was about 5 years old.

20

Originally Posted By: rsummers
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Some manufactures give you a chart that you can use to determine the charge based on the Line set size, length, and vertical rise. If you had good Installers who document the actual length of the line its possible to weigh in the charge. When I used to start the equipment I would always use the superheat or Sub-cool method.