What do you think of this Charlie B?


Check out the HVAC article.

Is this distributor tube restriction?
Or is this just a capacity/load change?

Has anyone checked this IR test out?
I have not. I do not use my IR outdoors much when it gets hot around here.

I am looking for IR scans where actual HVAC diagnostic testing has confirmed the anomaly.

Under charged, Over charged, low outdoor ambient, clean coil, dirty coil, high head pressure, …

Please contribute your scans and document the conditions when taken.

I too don’t use the IR a whole lot outside on the typical brick home around here in the summer. But after seeing a few different samples of IR finding “miswired” compressors and such I have started viewing all compressor with the IR to try and learn what they typically look like and possibly find anomalies. Cannot say that I have seen anything I think is significant yet.

The talk in the article about clogs is somewhat beyond my AC knowledge. I have seen compressors where the “heat bands” are not equal, but would not feel comfortable making a call on them at this point.

As far as the leaking ductwork in attics and between floors, I see that alarmingly often.

I have also thought that you might be able to pick up compressor fans running too hot. Seems that on a hot day here, after running for an hour or so, most I look at seem to be 120 - 140 F. Thinking that I might see one that runs really far out of that range and be able to comment on it. Thoughts?

I have called out some motors but…

there was rust on the side of the motor from heat
the amp draw was over nameplate max
attached is a motor just slightly over amp draw and heat.

also this is what a compressor should look like.
There is obvious cool refrigerant coming into the compressor to help cool it.
The cool should not reach the bottom of the compressor.

this a properly operating reversing valve.
Often you can not access these well.
there should be a definitive line between the hot and cold stuff in the valve
the refrigerant lines should be the same (depending on mode); two cold, one hot. The two of the same temp should be the same. If it is not, hot is leaking into the cool side.

Nice pictures David, thanks.

How did you get the compressor shot? Disassemble the unit?

It would seem that with some work this is an area that we could do “cool” things with IR scans.

David that condenser does not look right the thermal pattern is off I would have to see the hot gas manifold entrance into the condenser. I have never observed a blocked manifold in my life time the lines are to large for a restriction the compressor would have to be discharging pure sludge for that to happen I would have to question the guys images.

I have been off line for some time rain and satellites don’t mix well dumped 5.2 inches of rain this morning from my Gage


David this is the image from ITC I copied and pasted it here. That image was bothering me the darker band or red just below the name plate is just about the right height for the fan blades to be moving a higher CFM across the condenser. I think the guy was totally off in his call

I have seen a lot of distributor tube restrictions in Janatrol heat pumps, because their distributor lines are as small as capillary tubes. You can see the restriction in the affected tube as well as on the coil (Frost).

Under low load conditions, the refrigerant in the condenser will slow down and begin to cool off as it passes through the circuit, giving it that striped appearance they posted in the article. [size=2]The problem I’m having is that all of the stripes are equal. Restrictions are seldom equal in temperature between circuits. Now, if you had one circuit that was totally cold compared to the others, that would indicate a circuit restriction to me.

I think this is just another case of factual further evaluation required and not just using IR has in evaluation of system performance.

I have seen a lot of reference to identifying refrigeration leaks posted on the Internet. I have yet to figure that one out either!

I am also having an issue with “blocked/dirty” condenser coils.

HVAC systems change pressure/temperature/amperage draw minute by minute throughout operation. There is no way to say that any reading that you take whether it is electrical, pressure, temperature, infrared is an absolute indication of defect.

It’s probably a little ironic, but I have not done a lot of infrared research on the HVAC equipment like Charlie has. Maybe because subconsciously I realized the ever-changing conditions of the equipment make changes in the baseline infrared scans which make them useless. The definitive scans that I have taken (and posted above) are pretty absolute, but even the compressor gradient will change with load and length of run time from startup.
I guess I’ll have to start to catalog some more HVAC conditions and see what we come up with. I’m always looking for ways for home inspectors to be able to evaluate HVAC equipment without dwelling in the forbidden HVAC zone controlled by the EPA.

When checking an AC condenser with infrared, the coil image can tell you a lot about the condition and coolant charge. I know of no other way to detect coil restrictions.

Thermocouple, visual, non contact thermometer.

Most units have at least 6 sections, each fed by small (~1/8") tubes.

Photo caption says it is a 10 section coil? Is he counting stripes? I have never seen a 10 section coil in residential sized equipment that I can remember.

Their size makes them vulnerable to clogging.

There is almost always a filter or screen before a capillary type distributed tube and as Charlie pointed out, distributor tubes (not to be confused with capillary tubes on heat pumps) are substantially larger and not prone to blockage. If there is enough crap inside the refrigerant system to block a 1/8" tube, you have other serious problems.

If several become restricted, heat dissipation and efficiency are affected. A severe condition can result in liquid coolant re-entering the compressor,

This is hogwash in 99.9% of the cases. You can completely shut off the liquid line service valve and block all liquid refrigerant from leaving the condenser coil and it will not back up on the compressor unless the lines that run length exceeds the manufacturers design (in which case a receiver should have been installed in the circuit).

resulting in excessive wear and premature failure. This was reported with one of the units shown. (Note: Due to variations of condenser capacity, some manufacturers may not use every coil section, and one restricted section may not constitute a problem.)

Anyone have any information on this? Maybe he’s talking about a section of coil not even being piped into the refrigeration circuit?

A 10 section coil condenser less than one year old.
This one has a normal IR signature.

Some AC technicians have told me, they charge systems according to coolant line temperatures, rather than pressure.

I would certainly hope that 100% rather than some of the technicians would be charging the equipment in this manner! The refrigeration gauges is not like the gas gauge in your car! But you must install them to make sure the thing doesn’t blow up in your face!

I often used a ΔT of the condenser coolant lines, along with heat rise, and a ΔT of the air across the evaporator coil

you all know what I think about this one!

to evaluate the operation of central air systems. I have also used this method on commercial chilled-water systems, and residential geothermal units.

Using this method in water systems is appropriate because you only have sensible heat in a liquid state.

(Of course, copper is not a great emitter. Electrical tape or adhesive paper stickers are necessary for more accurate readings.)

P.S. I am not a certified thermographer.

I am wondering if he is a certified HVAC Tech either?!

I don’t think this article is accurate and do not recommend anyone adapting this as a common practice.

David I don’t think the guy was certified anything was just listing to what he wanted to hear from some HVAC tech and he did not understand what was being stated. He was just making it up as he went along, sounded good to the unknowing person. That would of made a good field assignment to turn into ITC they would not have known the difference.:smiley: :shock: </IMG></IMG>

Here is one from today. Opinions? Unit was not cooling.


Very hard to tell anything by just looking at one image but based on what I am observing in the pic it appears to have a cooler condenser than what I would expect this time of year the condenser may be matted over with lint which would not give a good thermal pattern to the camera. A unit with a high head pressure will have a corresponding higher suction pressure which in turn would have a higher evap temp thus less cooling abilities. My question to you would be are you stating the reason for no cooling is determined in your infrared image.

BTW a low charge of freon and a low head pressure could give the same results.

Nice pictures everyone

Pretty much based on it was not getting cold inside upstairs =) I don’t generally try to determine ‘why’ it is not cooling, just don’t have that expertise. But I like learning.

Also noted that the air from the conpressor fan was not hot on this unit, not transfering any heat, when i took the IR pic. Just took the pic because of this thread for you guys to look at. The one thing that seemed a little weird was that the freon line was relatively cold and sweaty (pretty hot humid day.) But there was definately no good cooling going on inside. 20 yo original unit, not in the bestof condition.

Charlie, I asked IR guys to post these scans here for baseline photos for my use. Provide the best explanation they can for their limited inspection SOP.

Kevin, You have one hot circuit with a too cool condenser. This would indicate a potential refrigerant distribution problem like the ITC article was trying to show.

A cool/wet suction line (which intrigues me) would not be there if it was low on charge or restricted. I would say we are not picking up heat at the indoor coil (did you have air flow?). Dirty coil, frozen/iced coil. If you find out the HVAC guys findings let us know, OK?

I’m grabbing my horse and heading for the mountains. No phone, no internet!
Like the “gone fishing” thread, I turned down three inspections so far and I’m not gone yet! :-o

Be back next week!
Keep posting pics!

Yes I understand you asked for the images and I hope they keep them coming. It was very obvious to me that no heat transfer was taking place at the condenser I thought Kevin might have some more information about the system that he did not post I was just digging for more info.

David there are no mountains in Tn you would have to travel to the Rockies stay safe don’t get bucked off I am waiting for you to return will call you

Sounds GREAT! Have Fun.

Sorry Charley,

The house was a poorly done flip for a first time buyer. There was sooooo much stuff to report that once I established it wasn’t working, the ductwork was falling apart, the other unit where they had replaced the compressor but not the evaporator coil , only half insulated the lines, filthy filter in newer unit (filter for the one in the pictured one was actually new), furnaces full of rust and scale, I just moved on.

Thought about the IR pictured for you guys but didn’t really give a lot of thought to other info you might need. Just reporting that a lot was wrong and the system wasn’t working to add to the 50 page report.

Can you maybe give me a list of things that would be useful to know to go with the IR pics? On most inspections I will have more time to spend extra on some research and can maybe give you more useful specific information.

A restricted air flow across the A-coil would make a good image find a downflow coil that has low air flow at the registers and a matted over blower wheel,a dirty or missing filter you will have a restricted coil. Some of the coil boxes have front covers that can be removed easily. A restricted coil should have a different thermal pattern from the bottom to the top of the u-bends. If you can get a shot of the suction line with no insulation installed where it enters the outside unit one could also see a difference in temp between there and the A-coil. I will also keep an eye out for one of these.

One that would be tough to find would be a compressor with bad discharge valves. When the discharge valves are not holding they leak high pressure high temp freon back into the suction side and increases the suction temp thus improper cooling and the image of the suction line would be much warmer than normal.

I have not taken an image of a dirty outside condenser perhaps both of us can find one as they are quite common in my area at least lots of cotton wood fuzz blowing this time of year. The condenser temp would be very high but I don’t know what the camera would show due to the insulation effect will have to check this out.