Thread: Infared theromoter at condenser

Can a infrared thermoter be used to check the temp . difference on a outside condenser , I have been using the old fashion bulb type, but was not sure how to use the infrared thermoter to get a accurate reading. thanks for any tips.

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Originally Posted by daniel nantell

Can a infrared thermoter be used to check the temp . difference on a outside condenser , I have been using the old fashion bulb type, but was not sure how to use the infrared thermoter to get a accurate reading. thanks for any tips.

You won't get an accurate reading with an infrared thermometer that way, you want to measure the temperature of the air and those don't measure air temperature.

Besides, why are you taking a temperature differential reading there anyway?

ditto

Best place to check temperature would be directly at the evaporator coil.

rick

Jerry, the Inspection report that I have asked for the Temp. Difference to see if its in the 12 to 20 degree range. thanks

Originally Posted by daniel nantell

Jerry, the Inspection report that I have asked for the Temp. Difference to see if its in the 12 to 20 degree range. thanks

Daniel,

Why are you trying to determine the TD at the condensing unit?

rick

You will find that your report program has a lot of crap you need to cut out and correct.

Best

Ron

Infared theromoter at condenser
Can a infrared thermoter be used to check the temp . difference on a outside condenser , I have been using the old fashion bulb type, but was not sure how to use the infrared thermoter to get a accurate reading. thanks for any tips.
__________________
dmn

What is a "theromoter/thermoter"?

(changed the "s" to "$")

Originally Posted by daniel nantell

Jerry, the In$pection report that I have asked for the Temp. Difference to see if its in the 12 to 20 degree range. thanks

Daniel,

That is asking for the Temperature Difference (TD) at the air handler unit inside.

However, now that we are on that subject ... it is a rather useless measurement to take, and most often the TD being looked at would be 15-22 degrees, but everyone has their own "guidelines" for that, none of which really mean anything.

I stopped taking TD many years ago as it was really meaningless ... worse than meaningless, it could be indicating a poor condition and you take it as indicating a good condition - the "meaninglessness" now become "meaningful" only you missed its "meaning".

Visually inspect the unit and the duct work, take the temperature of the supply air to make sure it is heating or cooling (depending on what you are checking).

Let's say you were looking for a TD of 15 to 22 degrees, you have a unit with low refrigerant, which would normally give a low TD, but you have a caked over return air filter and a collapsed duct above the air handler, both restricting the air flow through the coil, you read a TD of 16 and pronounce the unit as "operating okie dokie" - but it was not ... and no you have just mis-reported it to your client, so instead of getting it corrected or getting a credit to make repairs, they take it as is, and then it fails and they call an HVAC technician who finds what you should have found ... you do know where this is going, I am sure ...

By the way, you should be using the metal probe thermometer (dial type or digital) instead of those bulb types anyway for whatever you will be using a thermometer for when checking "air" temperature.

First I would change my report, remove the section that you use to report the TD. As Jerry said, TD's are just about useless. They make for a good session in the schools and an extra line in the various reports.

For years I have checked the refrigerant line at the condenser unit on split systems. If the line feels like an ice cold beer then I'm 95% sure that it is cooling properly. If it is warm, cool or frosting then it has a problem. If I have air coming out of the registers and it is cool (around 45-55f) then I can say that the system is cooling. Not all of my A/C inspections are that simple but for many it is about all that is needed to see if a system is cooling properly. With a package system I depend more on the air temps at the registers.

In my reports I only report that the system was either cooling or that it was not cooling properly at the time of the inspection. I do not tell how much it was cooling or was not cooling.

I am so glad this was posted today, as I had this problem with a recent home inspection that came up today -2 weeks ago. I did not denote the temp diff and after 21 days, the compressor went out. The home warranty company has told the new owner I missed it, however it did have proper discharge air temp, a lousy programable t-stat, it did start, did have a clogged air filter, which I suspect added to high head pressure, liquid cfc retuning to the unit, possible causing the failure. All ducts intact, 5 yrs old home. I called the training instructor with Champion realestate and he said the differential was part of the standards, but I cannot find it. Any TREC guy have this problem.

sm

deleted

(B) inadequate cooling as
demonstrated by its performance in the
reasonable judgment of the inspector;

Rick, this is as close as I can find to requiring reporting temperature differentials.
Can you point me in the right directions for what you are referring to?

Jim,

It was the line directly below quote you posted that stating TD's could be performed at the air passing across the evaporator coil.

It was not a requirement though and that is why I deleted the post.

rick

We are not there to be or should be expected to act as an HVAC tech. (Although I actually am)

For the purpose of the report, I simply check the difference between the return and the supply registers. If it is "functionally" heating or cooling, it gets a note to that effect with the comment that it is a good practice to have the unit serviced when they first move in to establish a "baseline" for a regularly scheduled maintenance program.

If it is not performing as expected the comment reflects that condition and a call for a specialist.
In either case, the specialist gets called for, either for diagnosis and repair or for a basic service call.

Originally Posted by Dana Bostick

For the purpose of the report, I simply check the difference between the return and the supply registers. If it is "functionally" heating or cooling, it gets a note to that effect with the comment that it is a good practice to have the unit serviced when they first move in to establish a "baseline" for a regularly scheduled maintenance program.

That is a good way to get the dreaded fat letter from their attorney, 'oh, by the way, service AFTER ... YOU ... OWN IT.

Not only is taking a TD pretty much useless, as an HVAC tech you should know that, but recommending the unit be cleaned and service AFTER closing is not in the best interest of you client ... maybe in the best interest of the seller, but the buyer is your client.

Use a new digital air-probe TH with a more precise increment reading.

I've worked HVAC as a licensed Tech since the mid-1970's.

The HVAC inspection is extremely important to the buyer.

There is always a proper testing sequence for determining if the HVAC system is functioning up to par. Too low an airflow through the evaporator is common!

1.) Determine if the condenser coils & fins, the indoor filter(s), blower wheel blades & indoor coil are clean. They have to be reasonably CLEAN or all other testing will be distorted.

2.) Actually when you check Model numbers, Tonnage Rating & SEER Ratings' of the condenser, then checking the temp rise is an excellent indicator of the amount for total BTUH, both sensible & latent, being transfered to the outdoors. Yes, even my HVAC ARI text books support this condenser split test. The higher the SEER the lower the acceptable Temp-Split.
"Air Conditioning System Sizing for Optimal Efficiency"
(Right Click Link & open in New Tab)

3.) You need an anemometer to ballpark check airflow velocity from the diffusers. CFM= (Velocity in FPM X's sq.ft area of the duct), or the diffuser' "Ak" listed sq.ft open-area is best to use.

4.) Total BTUH= (CFM X's 4.5 X's Enthalpy Change) Chart Link:
http://www.udarrell.com/wet_bulb_enthalpy_chart.pdf
(Right Click Link & open in New Tab)

You need an instrument to quickly check wet bulb temps along with ballpark accuracy airflow CFM to rooms.

Figuring round duct sq.ins. = 7" rd duct sq.in. area= 7X's 7=49 X's .7854 = 38.4846-sq.ins. / 144= 0.2672541 sq.ft area. X's say 600-FPM VEL = +160-CFM airflow. Say, seven runs all equal for this example; 160-CFM times 7= 1120-CFM, or 448-CFM per ton of cooling, a bit high but acceptable with some low humidity conditions for a 2.5-Ton A/C. (425-CFM per-ton with a wet coil is most acceptable.)

Well, anyway that is the easy fastest way to ballpark check an A/C or heat pump's actual performance. After you do it a few times it becomes second nature.

Practice figuring all this on paper.
Do Google searches among others' for, Hart & Cooley & J&J Register "Performance Data," you will see the "Ak" you can use listed on some of the diffuser's performance Data. - Darrell

Originally Posted by Dana Bostick

We are not there to be or should be expected to act as an HVAC tech. (Although I actually am)

For the purpose of the report, I simply check the difference between the return and the supply registers. If it is "functionally" heating or cooling, it gets a note to that effect with the comment that it is a good practice to have the unit serviced when they first move in to establish a "baseline" for a regularly scheduled maintenance program.

If it is not performing as expected the comment reflects that condition and a call for a specialist.
In either case, the specialist gets called for, either for diagnosis and repair or for a basic service call.

I tend to agree with Dana's statement. Ascertaining the efficiency is beyond our standard of practice [SOP's - CREIA/California]. Making a suggestion to practice "preventative maintenance" once you occupy a home is good advice, and as such one always needs a baseline measurement.

Per the other statements in this thread, in my opinion an IR Thermometer is and can be considered a more accurate measurement if you carefully select the measurement point both for solids and air.

All the best - Richard

The Texas Real Estate Commission requires all licensed inspectors in Texas to take a supply and return temperature. They do not specifiy where you take it. I take them at the air handler and for fun in a supply register and a return. I don't make the rules in Texas but I have to follow them!

Originally Posted by Bob Spermo

The Texas Real Estate Commission requires all licensed inspectors in Texas to take a supply and return temperature. They do not specifiy where you take it. I take them at the air handler and for fun in a supply register and a return. I don't make the rules in Texas but I have to follow them!

Bob,

I don't believe that information is correct. Where in the SOP's does it state the we have to take such temperatures?

No where do I see it states those rules below from the SOP.

FROM TREC

(b) Cooling equipment other than evaporative coolers. The inspector shall:

(1) report the type of system(s); and

(2) report as Deficient:

(A) inoperative unit(s);

(B) inadequate cooling as demonstrated by its performance in the reasonable judgment of the inspector;

(C) inadequate access and clearances;

(D) noticeable vibration of the blower fan or condensing fan;

(E) deficiencies in the condensate drain and auxiliary/secondary pan and drain system;

(F) water in the auxiliary/secondary drain pan;

(G) a primary drain pipe that terminates in a sewer vent;

(H) missing or deficient refrigerant pipe insulation;

(I) dirty evaporator or condensing coils, where accessible;

(J) damaged casings on the coils;

(K) a condensing unit lacking adequate clearances or air circulation or that has deficiencies in the condition of fins, location, levelness, or elevation above ground surfaces;

(L) deficiencies in mounting and operation of window or wall units; and

(M) deficiencies in thermostats.

Originally Posted by Jerry Peck

That is a good way to get the dreaded fat letter from their attorney, 'oh, by the way, service AFTER ... YOU ... OWN IT.

Not only is taking a TD pretty much useless, as an HVAC tech you should know that, but recommending the unit be cleaned and service AFTER closing is not in the best interest of you client ... maybe in the best interest of the seller, but the buyer is your client.

Jerry,
Looking at the delta T is a quick way to determine if it is actually workingl.

Per the CREIA SoP's

Heating and Cooling

A. Items to be inspected:

Heating equipment
Central cooling equipment
Energy source and connections
Combustion air and exhaust vent systems
Condensate drainage
Conditioned air distribution systems

B. The inspector is not required to:

Inspect heat exchangers or electric heating elements
Inspect non-central air conditioning units or evaporative coolers
Inspect radiant, solar, hydronic, or geothermal systems or components
Determine volume, uniformity, temperature, airflow, balance, or leakage of any air distribution system
Inspect electronic air filtering or humidity control systems or components

That does not leave a lot of room to get fancy.

Are you suggesting they have it serviced before they own the house?
I always recommend they have the system checked by a professional but if I call for further evaluation during the contingency on every system with no real basis of a defect to point to, why am I even there? There are many on this board that deride inspectors that defer everything to a pro.

Rick,

I stand corrected! It is not TREC that requires the temperatures it is the computer generated form that I use that asks for it! I do use temperatures before and after the coil to determine if "adequate cooling is being supplied" as required by TREC.

Bob,

I do the same myself, although it is not required.

rick

There are many reasons why merely taking the temp drop across the indoor evaporator coil can generate totally false signals - regarding proper A/C performance.

Airflow could be extremely low along with a low humidity, plus even an improperly charged system & the temp split could look normal around say 22-F. Airflow has to be within acceptable perimeters to achieve an accurate charge.

However, if you take the outdoor temp split it will show a very low split above the outdoor temp, indicated an underloaded indoor coil.

Now, lets say the indoor humidity is real high with perhaps even a high 450-CFM per-ton airflow. The split could be around 12-F & you would indicate a poor performing A/C.

Now, we check the condenser airflow split &m it is way above normal indicating a condenser/evaporator & system performing above its tonnage Rated BTUH.

The condenser split includes both the sensible & condensing latent heat load & is an excellent indicator of BTUH performance when coupled with the SEER Rating of the system.

Therefore, only taking an indoor split with no other data, like CFM airflow, humidity & the outdoor condenser heat ejection split, is NOT a dependable indicator of BTUH performance.

I say make your inspection checks meaningful & accurate or leave it to those techs That will hopely do it right.

You can easily ballpark the BTUH operating performance with the indoor data I illustrated above on my last post in this thread. - Darrell

Originally Posted by Jerry Peck

That is a good way to get the dreaded fat letter from their attorney, 'oh, by the way, service AFTER ... YOU ... OWN IT.

Not only is taking a TD pretty much useless, as an HVAC tech you should know that, but recommending the unit be cleaned and service AFTER closing is not in the best interest of you client ... maybe in the best interest of the seller, but the buyer is your client.

Originally Posted by Dana Bostick

Jerry,
Looking at the delta T is a quick way to determine if it is actually workingl.

Originally Posted by Darrell Udelhoven

There are many reasons why merely taking the temp drop across the indoor evaporator coil can generate totally false signals - regarding proper A/C performance.

Dana,

Darrell explained it more thoroughly than I did.

By the way, the CREIA SoP does not say what you think it does, or at least not what you implied it does.

Darrel & Jerry,
I know all that. But we are not there to determine the proper charge, airflow in CFM/ton, air balance, ASHRE heat loading of the structure, run a heat loss calc or any other technical determinations using gauges, air flow meters or wet bulb/dry bulb temps. (all of which I do have) That's all for the service person to do. My point is to determine if it is heating and cooling a little better than waving my hand in front of the register and guessing.
I know there are many pitfalls and potential errors but at least I know that its actually running and distributing heat or cool to all the rooms pretty quickly. As I said, I always recommend a full-on check out by a pro for their peace of mind.

I agree with all your posts, however, if you were to take the two air-temp-splits of the indoor coil & the outdoor condenser with side coil intake & upflow discharge, a comparison of the two provides much more important data.

You need to know the SEER of the condenser to make the temp difference more meaningful.

A large % of techs don't check condenser temp-splits, indoor airflow CFM, humidity or take a lot of other important data info. All anyone needs to ballpark the BTUH is the airflow CFM through indoor coil & the supply & return wet bulb temps.

Total BTUH= (CFM X's 4.5 X's Enthalpy Change) Chart Link:
http://www.udarrell.com/wet_bulb_enthalpy_chart.pdf
(Right click link, open in new tab.)

Maybe I expect too much however, the energy crunch is here & inspection codes may get more involved.

Far too many techs don't do zip to check actual operating performance! - Darrell

Originally Posted by Dana Bostick

My point is to determine if it is heating and cooling a little better than waving my hand in front of the register and guessing.

In that case you STILL do not need to take a TD, you simply take a supply temperature reading.

If you cannot tell from that the supply is warmer (on heating) or cooler (on cooling) than the air in the roof ... then you need to put your tool belt down ... now slowly back away from the a/c-heating system ... and call an HVAC contractor to do your a/c-heating system inspections.

45-55 air out of the supply vents is toooo low. It will cause condensation to form on the vents and create rust and mold deposits unless the humidity is near zero in the house. But if that is the case then the occupants probaly have been zapped so many times by static electricity i guess it wouldn't matter. You can also, tell how a unit is running by taking the temp diff across the outside coil as wellas it is much the same if you know what the mfg calls for. Not all units are the same even for the inside temp drop or raise. It is just an observation at a given moment of time. The infrarad thermometer will give an accurate temp outside as well as the inside, what is the difference, you just point it to the metal the air is blowing through just the same as the supply vent, you are really taking surface temp any way unless you have a good electronic theromemter that is specifically designed to only take air temp. in that case it has to be in the air stream and then will only be a degree or two different between them. If you have a varible flow fan with dirty filters and a low or over charge do any of you know what kind of temp diff that will create and would you report that cond.
But yes without any more on the subject with the s--t load of formulars provided, most forms ask for the temp diff. Between the inside suppy and return grills only.

I used to take TD measurements in the beginning for a little while and then woke up one day and realized I knew better. As Darrell showed there are too many variables that come into play to be a realistic measurement during an HI. I put the stat to a particular set point and see if the system can reach it in a reasonable amount of time. Also of course check what we all should be checking.
Just did an insp on Friday. Return in all 3 1st floor bedrooms, no return in any common area of the 1st floor such as living/dining rooms or hallway. Living room has large western exposure bay window.
The client doesn't give a damn about a TD line item he will never understand anyway. What the client cares about is knowing that in the summer he will boil in that living room every afternoon regardless of how much AC gets pumped in. Providing a service that is relevant to the client is what matters.
Also let the client know that the bedrooms will probably never stay warm. I have nothing against returns in bedrooms but when a duct system is that imbalanced, there will be other problems.

Am I wasting my time posting here?

Knowing the indoor humidity level & some sense of what the airflow is through the indoor coil is very important data to record.

Cobra Cook made some very important points concerning low supply air temps & mold, which is what inspectors look for.

If you don't have a simple MPH meter or FPM anemometer (which IMO you ought to have) then practice judging airflow MPH with the back of your hand or front of your wrist, or practice with an 8X11 sheet of paper. Listen to the weather & with practice gain a sense of MPH velocities.

As Cook stated, when airflow is way too low, the temp will be too low & lead to mold, & register sweating in even 50% humidity air, etc.

Simple airflow math:
MPH X's 88 = FPM.
Where easily accessible measure the size of the branch take-off duct runs.
A rd 5" duct 5*5= 25 * .7854= 0.19.635-sq.ins. / 144= 0.1363541-sq.ft.
A rd 6" duct 6*6=36 * .7854= 28.2744 / 144= 0.19635-sq.ft.
A rd 7" duct 7*7=49*.7854= 38.4846-sq.ins., / 144= 0.2672541-sq.ft.
A rd 8" duct 8*8=64 * .7854= 50.2656 / 144= 0.3490-sq.ft.

Use diffuser's open surface area (listed Ak area) in sq.ft., *X's velocity in FPM = CFM.

Example 0.19635-sq.ft. area * 616-FPM = 164.6-CFM airflow (or 7-MPH)

With seven equal CFM supply registers(164.6-CFM *7= 1152-CFM / 450-CFM per-ton of cooling = supports 2.56-ton cooling, or a 2.5-Ton system.

It doesn't take much experience to know when the airflow is too low, & that is the situation in a large percentage of larger A/C & heat pump systems.

An efficient operating HVAC system is a homeowner selling point therefore, they could call for a pre-sale inspection, - that is a real plus for the buyer as it increases comfort levels & can greatly reduce utility bills.

Due to the Energy Conservation movement, Inspection Codes ought to make some of these simple evaluations mandatory; & definitely so for HVAC Service Techs. Far too few Techs do proper airflow evaluations!

Am I wasting my time? -udarrell

No. Some times the answers just get blown way out of proporation from a home inspection point of view.

For those who want to do testing beyond regular HI, look into Fieldpiece instruments. They are specifically designed for HVAC, price is good, they work well and last. You can get the main electrical tester head of your choice and add various attachment heads as you go along. Mine don't usually come out for regular HI, but sometimes if I am suspicious.