Darrell's AC Trouble Shooting Chart - Follow procedural checks below the chart! AC Overview |* Sizing Units for Adequate Airflow |* Condensing Temp CT Diagnosis - New
Please Respond on my Blog; let me know if you can't post: Ballpark Checking A/C Performance Check comp. discharge line 6" from Comp. 225F or Less!
"Higher" or "Lower" than "Normal" (PRINT CHART)
liquid High-Side Sub- cooling
NORMAL - (norm) - LOW - HIGH - Variable
Suction L.
(1) Suction Line Restriction - Upstream Between Service Port & E-Coil
(1a)Suction Line Restriction - Downstream from Service Port & Compressor Screen
Norm to High
Norm LOW
(2) Liquid Line Restriction - Poor humidity control
(3)Evaporator orifice oversized or bypassing - or TXV Overfeeding - Normal Charge - with orifice feed Poor humidity control HIGH
norm to low
(4) Hot gas Disc. Line Restriction
(5) Inefficient Compressor - Also, see (3) Above - Poor humidity control
(6) Unbalanced heatload on Evaporator Circuits; or Insufficient Evap Heatload - Poor humidity control
(7) Insufficient Evap. Airflow, or Heatload - Poor humidity control
LOW LOW LOW Norm/high
(8) TXV Refrigerant Overcharge- High or Low pressure - Variable
according Outdoor Ambient Temperature & to indoor heatload - non-TXV
(9) Insufficient Low Charge - Piston Orifice Flo-Rater
- with orifice feed Poor humidity control
(9a) Insufficient Low Charge with TXV Wide Open
may be-Normal
may be Normal
(10) Excessive Evaporator Heat Load - Latent & Sensible + High Latent + high indoor airflow HIGH
(11) Ht Pump low head low sub-cooling; leaking check valve; both modes|SOV=switch-over-valve - rev/V leaking or bad coil depends/charge
+/- normal
could be normal LOW LOW LOW
(12)  Very High Temp Ambient Air Entering Condenser or dirty - Low condenser airflow - with orifice feed Poor humidity control HIGH HIGH HIGH Norm/low HIGH
Contractors An Important Efficiency Instructional Video - 4 All Home Owners Too - Last Half Best
The New Digital imanifold gauge estimates CFM and Provides Btu/hr Performance - On YouTube
More authenticated survey test corroboration; the surveyed HVAC systems were systems that they had complied with their program’s energy standards and "all had received substantial incentive payments," but delivered an average of only 63% of their Rated Btu/Hr to the homes & 50% of the required airflow. http://bit.ly/1adKKG6 - We can fix these costly wasteful problems! Electric Company Energy Efficiency Programs - pdf.
70% of homes in California are operating at 50% capacity. - California Energy Commission
http://www.law.cornell.edu/uscode/text/47/396 (8) public television and radio stations and public telecommunications services constitute valuable local community resources for utilizing electronic media to address national concerns and solve local problems through community programs and outreach programs...
Example of typical furnace over-sizing; my former oil furnace & the other house here on the farm both had 140,000-Btu/hr input oil furnaces installed when new they were 80% efficient; 140,000 * .80% is 112,000 * an 85% nozzle is 95,200-Btuh.
The homes both load-calc Design at -15F between 26,000 to 32,000-Btuh; therefore a 38,000- Btuh will easily handle the heat-loss at any extreme temperature. 95,200-Btuh / 38,000-Btuh is +2.5 times the proper Btuh sized furnace. 38000 * 2.5 is 95,000; left the fractions off the 2.5...

First, always check for Return Air/Supply Air duct leaks, seal them with approved mastic, check CFM airflow rate and that the coil fins and blower wheel blades are clean! "Check for Insufficient Air Flow Across Evaporator Coil" - Check for: dirty filter, dirty lint clogged evaporator, blower speed tap selected, or belt and speed adjustments, blower motor,  check any belts for wear and proper tension, dirt lint loaded blower wheel, and out of specs or wrong rated run capacitor.


  CFM = (Input BTU x thermal efficiency - Furnace OUTPUT) / (1.08 x temp-rise DT) or use 1.1

  Note: Combustion efficiency can be used in place of thermal efficiency.  

  DT is the temperature rise across the heat exchanger in degrees Fahrenheit 

  This will give you an approximate CFM; although it will be very close to the actual if the measurements are made accurately and the input of the appliance is correct 


For an electric furnace the airflow measurement procedure is the same.  Allow the appliance to operate until the temperature rise stabilizes. Measure the temperature rise again out of the line of sight of the electric heater, along with the incoming volts and current draw in amps to the electric strip heaters.  Enter the information into the following formula 

  CFM = (Volts x Amps x 3.41) / (1.08 x temp-rise DT) 

For fuel oil the procedure involves verifying the nozzle size and the correct fuel pressure.  After the Nozzle size in GPH (gallons-per-hour) is known and fuel pressure set to the listed data, the combustion efficiency must be measured with a stable stack temperature, and the temperature rise across the heat exchanger recorded

CFM = (Input BTU x thermal efficiency - Furnace OUTPUT) / (1.08 x temp-rise DT) or use 1.1

Check airflow system static pressure. Verify Blower Performance --by checking blower air handler "Static Pressures with the specific model's Blower Curve Charts." At a specific heatload condition, Optimize the conditioned space's heatload on the evaporator coil to optimize the rated Btu/hr and EER, and/or SEER Ratings. Always Check comp. discharge line 6" from Comp 225F or Less; cylinder walls 75F higher!

Even experienced HVAC technicians are not properly charging the thermostatic expansion valve (TXV) refrigerant metered systems, because instead of only charging to the sub cooling standard they are interposing superheat into the equation leading to grossly miss charged and especially grossly under charged systems.

First; they never or rarely ever check or verify that there is the proper amount of cubic feet per minute (CFM) of airflow through the evaporator coil before attempting to balance the refrigerant charge; that should always be done first.

The thermostatic expansion valve (TXV) totally controls the superheat (SH) setpoint target; NOT the charging of the unit; a TXV set-point which could be a Fahrenheit set point of anywhere from 20F down to 10F on an air-conditioning system or 8F SH on a heat pump.

The technician I witnessed had a wonderful digital readout manifold gauge showing superheat and sub cooling, the unit only had about 1F sub cooling to begin with and he proceeded to get to a mere 4F of liquid sub cooling adding one pound of R-22; the normal range is 8 to 12F sub cooling (SC) on those older 12 SEER and lower systems.

That the technician erroneously said was that most TXV systems are targeted at 16F superheat and so since it was at 14F SH; and it was still hunting due to a lack of a solid liquid stream to the TXV; the reason that he falsely speculated that the system was over-charged was because it wasn’t holding his imaginary 16F superheat target; that's because the TXV was a 14 or maybe 12F or less superheat target-point TXV.

The TXV superheat target of this particular UNIT might be 14F, or it might be 12F or even 10F therefore it is totally wrongheaded to be using it when charging to falsely think it would lower superheat & then to quit charging at a mere 4F sub cool & NOT continue to the required sub cooling standard. To do so could leave a lot of new and older TXV controlled evaporator coils way under charged.

Troubleshooting an air-conditioning system using superheat and sub cooling:

Troubleshooting is a matter of using temperature differentials; after retirement, I've used temps for SC without using a manifold gauge for many years. .
A Fixed Orifice ‘Piston’ metering device; charge using superheat; troubleshoot using both superheat and sub cooling:

Sub cooling temperatures tell you if you have too much or too little liquid refrigerant in the condenser high side; superheat temperatures tell you if there is too much or too little liquid refrigerant in the low side, - in the evaporator coil.

A too high superheat and a too low sub cooling indicates you don’t have enough liquid refrigerant in the both sides therefore low on charge.

A too low superheat and a too high sub cooling indicates you have too much liquid refrigerant in both sides or an overcharge.

Both, a high superheat and a high sub cooling more than 15F SC indicate a refrigerant system restriction; same with TXV system, TXV may not be able to bring SH down to its target.

System problems with a TXV metering device:

Refrigerant overcharge suction pressure normal & liquid pressure HIGH; superheat normal sub cooling HIGH; amps high and RH control normal

Refrigerant under charge: suction pressure normal; low liquid pressure; low superheat ;normal too high; sub cooling LOW; amps low; relative humidity control is normal.

Liquid restriction: suction pressure low liquid pressure low; superheat high sub cooling high; amps low and will eyes with poor real humidity control.

Low evaporator airflow: suction pressure low liquid pressure low superheat normal sub cooling normal amps low may ever me eyes with normal real humidity control.

Dirty condenser: suction pressure normal; liquid pressure high; superheat normal sub cooling normal ;amps high ;humidity control normal.

Low outside ambient temperature: suction pressure normal; low superheat; normal sub cooling; low amps; normal RH control.

TXV bulb loose: suction pressure & liquid pressure HIGH; AMPS HIGH; superheat & SC LOW; below sub cooling; HIGH amps; poor RH control.

TXV bulb lost charge: suction pressure low; liquid pressure low; superheat sub cooling HIGH; amps low; ICE/poor relative humidity control.

TXV bulb poorly insulated: suction pressure & liquid pressure HIGH; I superheat low sub cooling low; ;Amps HIGH; poor relative humidity control. - udarrell

Non-Condensables: suction pressure normal, liquid pressure normal; sub cooling normal; amps HIGH; poor relative humidity control sometimes normal control.

Some easy simple ways for anyone to check the performance of their air-conditioning system
Best ROI Investment or Lose the Investment money annually "Home Energy Efficiency Pays You." Video

Try to check the run time and off-times of the air-conditioning system and write down the indoor temp & %RH -humidity & outdoor temperatures; it's best to do this on the hottest days & late in the afternoon around 4pm.

Let's say the air conditioner runs for 15 minutes then, off for 15 minutes before it restarts, that's a total of 30 minutes for complete cycle so you take 15 minutes and divided by 30 minutes and you get .5 or 50% runtime; let's say I have 2 ton air conditioner; 80-F & 50%RH indoors & 95-F outdoors could yield 24,000-BTUH; however, due to ductwork and other factors it would not deliver to the rooms 24,000-Btu/hr instead figure 90% of 24,000 and multiply that figure 21,600-Btuh delivered to & from the rooms by * .5 extrapolated that is only 10,800-Btu used per an hour to hold the 80-F temp. Then you should perform a free online load-calc to verify how well your A/C or heat pump is performing.
That formula can be used for any complete time span cycle. Some duct systems are only 50 or 60% efficient, result, huge losses!

 Another formula is the EER or 'Energy Efficiency Ratio' formula; the BTU/HR  divided by the wattage used. Another way to use the formula is to take the BTU/HR and divide by the units EER Rating. SEER Ratings are rather irrelevant as in the field they never equal their LAB Ratings.

Let's say the air conditioner has a nominal rating of 24,000 BTU per hour divided by a 9.7 EER that is 2,328 Watts of power used. A technician can then take an amp-probe reading and multiply the amps times the checked voltage which will equal Watts the unit is actually drawing. From that reading you can figure what its actual EER is; 2,328-watts / by 240-volts would be 9.7-amps.

Another way to verify what your home's Btuh load is, is to do a load Calc; I'll provide you with the free online load Calc with which you can experiment with until you get a proper load Calc performed, which you will then have to print out because you cannot save your load Calc's.

You can also use a indoor humidity gauge and write down the humidity level while taking the temperature difference between the supply air and the return air in your home; then go outside and take the temperature of the discharge air and subtract the outdoor temperature from it.

On a 10 or 12 seer condenser the indoor split at 50% relative humidity and 80F indoors should be around 19 to 22F. The outdoor condenser split should also be between 19 and 22F; the condenser fan is moving considerably more air through the outdoor coil than is moving through the indoor coil. A 13-SEER would be 20F temp rise off the outdoor condenser; & a 21F indoor temp-split.

Do the same with heating; say the gas furnace is an 80,000-Btu/hr at 95% efficiency which equals 76,000-output; if the runtime is 20-minutes on & 15-minutes off time before a restart, 20 + 15 is 35-mins total complete cycle time so, 20-runtime / 35 cycle-time is .57% * 76000 extrapolates to 43,320-Btu/hr used to maintain the Room-TH setpoint of say 70F. If this were the coldest winter temp; then a 57000Btu'hr output furnace would be better sized, as it takes at least 3 to 5-minutes to reach nominal output each cycle; cooling mode takes around 7-minutes, therefore the Btu-output would be less than what I showed above for cooling & here for heating; short cycles are inefficient & costly.

Filter sizing: ACCA Manual D requires a low 300-fpm velocity through a new clean filter; a 60F temp-rise maximum means the 76,000 will have close to 1200-CFM / 300 is 4-sf * 144 is 576-sq.ins of open-air-filter-area, media type filters only have a 65% open-air-area. 576 * 1.65 is 950-sq.ins of filter area. Two 16X25 is 400-sq-ins *2 is 800-sq.ins; still 150-sq.ins less than called for.

Above 500-fpm velocity debris blows through a media type filter. One 16X24 filter has a Ak of 1.84 @ 300-fpm it will only flow 552-CFM; @ 650-fpm it will flow 1196-CFM; that is 150-fpm above where debris begins to blow off excessively at 500-fpm velocity through the filter. Hart & Cooley Filter Engineering Data using media type filters.  A 1" deep pleated filter has way too much pressure drop resistance, use 4 or 5" !

Totally Free Load-Calc  
This Free online calc will help you determine equipment sizing & point-out areas that need efficiency retro-work - Once you calculate the page it saves the inputs for up to 24 minutes or, until you change inputs or close your browser.
You can
easily reduce infiltration rates yourself, therefore, I’d use 0.4 ACH (Air Changes per Hour) be sure to add the (Air Changes per Hour) CFM into the ‘Fresh Air Recommended ‘line-slot, or it won’t figure the Infiltration & fresh air Btuh.

You can experiment with changing the design temperatures in both heat & cooling, (or start-over showing the New Retro-R-Values) also to see whether the equipment exceeds, at those particular temperatures & new retro conditions, (exceeds) the Btuh calculation load numbers, 'in each' of the 3 cooling categories; Total Btuh, Sensible Btuh & Latent Btuh

Simple easy anyone can do ways to check the performance of your central air conditioner so, if needed, you can call an Energy Efficiency HVAC Technician

If U want me to run a ballpark analysis of how your system is performing in respect to its 'Nominal Rated Btuh' we need at least the following numbers:

Performance Data Collection – Best Time to collect data is Late afternoon around 4:30 pm, when attic is HOT; also when outdoor temps are around 85; 95; 105F or, anywhere in between.

 *All U need is a good thermometer (digital reading in tenths preferable) & and indoor Humidity Gauge

1) Helpful; Tonnage & SEER of Unit & outdoor condenser model number: __________________

2) TXV or, orifice metering device? _______. Only if U know…

3) Outdoor condenser’s discharge-air-temperature ______-F

Subtract Outdoor air temperature: _______

Outdoor Condenser Air-Temp-Split _______ 

4) Need the ‘Indoor’ percent of relative humidity - away from Supply-Air outlets ______

5) Indoor Return-Air Temperature ______

Subtract Indoor Supply-Air Temperature ______ -F

 Indoor temperature-split _______-F 

Need the above information for troubleshooting & performance analysis.

Example below:

A Goodman 2-Ton 13-SEER condenser, 800-cfm indoor airflow; 80-F indoor dry bulb & 50% relative humidity; Indoor temp-split 18 to 19-F.

@ 85-F outdoors; 103.9-F - 85-F outdoors or around an 18.9-F temp-split; 

@ Indoor 75-F & 50% RH condenser temp-split is only around 14.9-F.

In summer an all electric farm home TWO Half-Ton Window A/Cs & basement large dehumidifier:

June 30, 2012; Darrell’s meter; 62610 – 62140= used 470-KWh * .0985= $46.295

Find me at:

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HVAC Efficiency Overview My Audio overview; listen while you do other things
*Video checking static ESP *Video 2 checking static ESP View! Got DSL 11/2010

The Basics Featuring the Testo 556 - Video of a thorough A/C Testing setup 2/26/11

First, Check Return Air (RA) at grille & at entry of blower for heat gain, due to Return hot Air leaks.

Where air handlers' are set over Return Air Chambers, check for air leaks through the sheet rock & down the wall studs from  the attic - this is a fairly common condition that will overload the AC system with attic heat!
Why Home Energy Efficiency Auditing is important to our future Jeremy Rifkin Video
Air Conditioning Rip-Off Scams
Everything You need to know about HOME INSPECTIONS
MY HVAC BLOG - YOUR QUESTIONS & COMMENTS WELCOME  Go to my blog for the required trouble-shooting Data to Record

Airflow has to be optimal within specs, before the refrigerant charge can be correctly balanced for efficient operation!
Affordable Test Instruments Techs Must Own & Use!
All I had was the Sling Psychrometer & spinning it was a bit time consuming, but I used it religiously, it is information you need. 

The Testo 605-H2 Humidity Stick (wet bulb), displays relative humidity, air temperature and wet bulb temperature.

It is very affordable & because of its potential to help deliver tons of other data everyone should have one

For more information on it:

The other test data you need is the system's CFM airflow through the evaporator coil, then with software I have you can peg the BTUH the operating unit is delivering under those conditions.
Add to that a low cost Magnehelic gauge to read static pressures to compare with mfg'ers blower performance charts; plus a velocity meter & you have a ballparked CFM to plug into for the BTUH.

We could easily provide a detailed psychrometric print out what the operating system is delivering in BTUH, including condensate lbs/hr, & actual sensible & latent cooling BTUH & Ratio, every data detail imaginable. - Darrell

Air Conditioning Performance Diagnosis using listed (CT) Condensing Temperatures
Using Goodman 16-SEER "Expanded Performance Data"

  Find the correct (CT) Condensing Temperature with the following known mfg’ers data.

Outdoor Ambient Temp (OAT) 85-F; IDB 75-F; IWB 63-F or 50%-RH.
Listed pressure is 316-psig, or 99-F CT; that is 99-F -85-F is a 14-F SPLIT.

The delta T or temp-split should be within a 10-psig range or, +/- 2-F degrees; 97 or 101-F.

The mfg’ers Supply Outlet should be able to provide Contractors & Techs with those performance data charts. Goodman has their “Expanded Performance Data” on the Internet. BTUH = CFM X enthalpy difference from Chart X 4.5


Check Return Air (RA) at grille & at entry of blower for heat gain, due to hot Return Air leaks.
Where airhandlers' set over Return Air Chambers check for air leaks through the sheet rock & down the wall studs from  the attic - this is a fairly common condition that will overload the AC system!

For efficiencies sake measure the Return Air duct/chase area. If it's a round duct measure the inside diameter, I'll give you the sq. ins. formula on another pages; if square or rectangular multiple the two dimensions for sq. in. area. The sq.in. Return Air throughput ducting area should equal or exceed the Supply Area ducting.  In the far north smaller A/C units Verses the new larger heating blower units can mean too much CFM for the A/C's smaller BTUH capacity. Thermostatic Expansion Valves (TEV / TXV) systems should be set for a minimum 10 Degrees Superheat.

NOTE on 3 & 5 Above: If suction is high & head is low it is not necessarily an inefficient compressor, it could be (3) three.

"An oversized orifice or overfeeding TXV refrigerant metering device" could cause high suction & low head due to normal compressor pumping capacity being incapable of keeping up. An oversized unit might handle the sensible load but never do anything with the latent load as the conditioned space temp falls.

"Overcharging" will raise suction pressures & E-Coil temperatures & though it may raise head pressures, it does not always raise head pressures. The reason for this is that it reduces the capacity of the evaporator to absorb both latent & sensible heat & therefore reduces the actual heatload on what may possibly be an oversized over-capacity condenser coil.

Of course, an inefficient compressor could cause this problem; however, I would always do the Superheat & Subcooling checks & look for an
overfeeding metering device as well as an overcharged system, along with other possible causes, before ever condemning a compressor.

(8) NOTE: Refrigerant Overcharge: amp draw is HIGH when under a heavy heatload and can be LOW when overcharged but under a light heatload; both the condenser and evaporator are then overloaded with liquid and there is not enough of a heatload to evaporate sufficient amounts of refrigerant in the E-Coil to INCREASE PRESSURES and pumping WORK.

After any duct work or other changes and before you make any recheck tests, it is very important that your condenser coil, evaporator coil, and indoor blower wheel be squeaky clean.

Take the condenser entering air temp and leaving air temp, subtract for the temp-split. As a double verification: You can use the manifold gauge high-side (SCT) Saturated Condensing Temperature-dial-reading minus the outdoor-ambient temperature; the difference gives you the condenser temperature/split. There is NO excuse for not utilizing this simple btu/hr operating capacity diagnostic check. Always use an accurate volt meter and amprobe to make sure you are not overloading the compressor's amperage Service Factor and check the compressor discharge line to see that it is under 225-F.

Optimizing the "Evaporator HeatLoad" will Optimize the Condenser BTUH HeatLoad Output from your Home

Most evaporator coils are under-loaded when operating at the normal room temp setting!

The airflow should be adjusted to fully load the evaporator coil at the normal room temperature setting! This airflow adjustment will optimize your air conditioner's BTUH and SEER performance. Most air conditioner's have an underloaded evaporator coil at the room temp thermostat setting, where the vast majority of its run time will take place! In 8 foot ceilings, Return Air (RA) should always come from the warmer ceiling air areas.

On TXV metered systems the Subcooling should be within +/- 2-F of the mfg’ers installation instructions.

Air Conditioning Performance Diagnosis using listed (CT) Condensing Temperatures

Using Goodman 16-SEER "Expanded Performance Data"

What is the correct (CT) Condensing Temperature with the following known mfg’ers data?

Outdoor Ambient Temp (OAT) 85-F; IDB 75-F; IWB 63-F or 50%-RH.
Listed pressure is 316-psig, or 99-F CT; that is 99-F -85-F is a 14-F SPLIT.

The delta T or temp-split should be within a 10-psig range or, +/- 2-F degrees; 97 or 101-F.

The mfg’ers Supply Outlet should be able to provide Contractors & Techs with those performance data charts. Goodman has their “Expanded Performance Data” on the Internet.


Quick Check for Sizing Units to enough Airflow

Actually, even on service calls where there are cooling problems the ductwork should have a quick Manual D performed.

Then take the ESP static pressure & compare to blower graph or chart, also take the FPM duct velocity.

Then do a quick estimate of airflow per equipment tonnage.

To find area of a round duct; Duct diam is 7"; 7"X7"= 49-sq.ins., X's .7854 = 38.04845-sq.ins divided/ by 144= 0.2672541-sq.ft. area X's FPM Velocity 600-FPM = 160.35246-CFM X30 = 4,810.5738 each 7" run X's 6 branch runs = 28,863-BTUH, or airflow for 2.4-ton.
(12,000-BTUH /400-cfm per-ton = 30-BTU per cfm ratio | / 450 = 26.666-BTUH per-cfm)

That would also be good for 2-ton; at 550-FPM velocity X's 0.2672541= 147-CFM X 30 = 4,410-BTUH each run X 6-runs = airflow for 26,460-BTUH.

*Never sell units requiring more airflow than the duct system will support! - Darrell


This linked page is strictly a SUPERHEAT TABLE  Print these Tables & use them!

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First, thoroughly seal all ductwork with an approved mastic & get air flow correct!

How installing a 3-ton system can become a 1.5-ton system of actual delivered cooling (SURPRISE!):

To get the gross BTUH Heatload the Evaporator (DX) Coil is absorbing (which includes both latent, sensible heat) (These are ARI Formulas)
First, determine the Gross Rated BTUH the condenser is ejecting. 
Condenser’s Gross Btuh = Condenser’s rated CFM X’s Temp Split X’s 1.08

The chart split listed below is at Condenser Design conditions: Indoor Return Air 80-F dry bulb 67-F Wet Bulb or 50% Relative Humidity as you go up to 99% RH the condenser split could increase by up to 6-F; down as much as 4-F at a low humidity of 55-F Wet Bulb.

The chart split listed below is at Condenser Design conditions: Indoor Return Air 80-F dry bulb 67-F Wet Bulb or 50% Relative Humidity as you go up to 99% RH the condenser split could increase by up to 6-F; down as much as 4-F at a low humidity of 55-F Wet Bulb.
Do your own figuring based on this formula. Motor BTU/hr additive = Watts X's PF x's 3.413 for Btu/Watts additive added to rated BTUH, divided by condenser fan CFM X's 1.08 =  condenser Temp-Split. Get the Motor "Power Factors" (PF) of the compressor and fan motor from the manufacturers. Some Splits rounded.

CONDENSER TEMP-SPLITS - Comfortmaker 12-SEER units - used 0.90 Motor Power Factor - didn't need to use PF in formula
1.5 T  18,000  +17.5F Split > 18 >21-F split Cond. CFM 1400 | WATTS (1.591KW) 1591-watts plus 425-watts indoor blower-mtr; 2,016-Watts. X.90=1432x3.413=4,887+17500=22,389/1400=15.9x1.08= +17.5F condenser temp-rise (best not to use PF in formula)
2-Ton  24,000  23-F Temp-S  Cond. CFM 1400 | WATTS (2.067KW) 2067x.90=1860x3.413=6349+24000=30349/1400=21.7x1.08=23.4
2.5-T  30,000  21-F Temp-S  Cond. CFM 2000 |WATTS (2.778KW) 2778x.90= 2500=8533+30000=38533/19.2x1.08=20.8
3-Ton  35,600 14.8-F T-Sp    Cond. CFM 2800 | WATTS (3.096KW) 3096x.90= 2786+35600=38386/2800=13.7x1.08=14.8
3.5 T  42,500  17.6-F T-Sp    Cond. CFM 2800 | WATTS (3.578KW) 3578x.90=3220+42500=45720/2800=16.3x1.08=17.6
4-Ton  48,500 19.5-F Split     Cond. CFM 3400 | WATTS (4.174KW) 4174x.90=3756.6x3.413=12821+48500=61321/3400=18x1.08=19.5
5-Ton  59,000  23-F Temp-S  Cond. CFM 3400 | WATTS (5.043KW) 5043x.90=4539x3.413=15,490+59000=74490/3400=21.9

CONDENSER TEMP-SPLITS - My Brother's Heil 12-SEER Condensing Unit 
1.5-Ton - Rated at 17,500-BTUH,  Condenser fan CFM 1400 (Total Cond. Watts 1591 X's PoweFactors 0.90 X's=  1432  X's * 3.413 =  4887-BTUH Motor Heat additive +17,500= MotorPower "Rated Gross Heat Ejection" is 22,387-BTUH / 1400= 15.99-F x 1.08= 17.27F Temp Rise Cond/Split. His condenser only gets a 10 to 12 temp rise split, the evaporator appears to be under heat-loaded or, an unbalanced heatload on the DX coil's circuitry. 

The probable cause is "an unbalanced airflow heatload through the evaporator coil. "It's a (Thermo Pride OL 11 oil furnace). Those oil furnaces have a very large round heat exchanger that goes to near the top of the furnace, --due to a low basement ceiling the DX coil sets perhaps illegally close to the heat exchanger causing a few of the coil's circuits to be under heatloaded. Since the liquid refrigerant is not completely evaporated it will cause the outlet line that the TEV sensor bulb is on to be too cold and the TEV will shut-down the flow, which greatly reduces the BTUH capacity of the DX coil and the system.

On piston refrigerant control systems, they may flood back liquid which could damage the compressor, unless the system is way under-charged. Thermo Pride could install airflow turning vanes just above the heat exchanger to funnel the air directly into the DX coil, instead of most of the airflow hitting the bottom of the DX's drain pan causing extreme turbulence back-pressure and an imbalanced circuitry DX coil heatload!
His unit could also have some low temperature solder trapped on the screened entrance to the TEV evaporator metering device. If there is a gurgling noise& temp drop there, any restriction there would also lower the capacity of the cooling coil.
If your A/C unit is not cooling adequately & is costing you a fortune, the first thing to look for is hot air getting into the Return Air duct system, that would overload the evaporator & condenser & run your costs way up. What is the F-Temperature rise/split from the outdoor condenser above the outdoor temperature. 

So, your unit is costing you a fortune, I need to have the temperatures below, - that you can easily take for me:
“Copy only the data portions & paste in your Word-Processor, make a couple hard-copies, then send me what you take, & get as much of this data as your Tech will provide for you.” You can delete the (You &/or Tech) before you make hard copies for your Tech. Techs & HVAC user's, please use to your heart's content.

This is very important: Always tell the tech that you want all the data he takes clearly recorded on the Service Receipt!

I can run the temperatures data you take with an accurate CFM Airflow & ball-park the Nominal BTUH your new A/C is delivering, at those conditions.


For my information concerning summer design & your climate, provide your state & nearest large city __________
TONNAGE of Unit or outdoor condenser model number: ___________ You
TXV or orifice metering device? _______You or Tech, - not real critical to this analysis

Outdoor condenser’s discharge-air-temperature _____You
Out-Door temperature: ____You
Condenser air Temp  split _____You

Indoor Total-ESP - External Static Pressure  _______Tech
All Supply Air velocities in FPM: ___Tech
I’ll do the math for the total CFM:

Suction line pressure ___Tech
Suction-Vapor line temperature: ___Tech
Saturated Suction Temp – Gage - Suction Saturated Temperature. ___Tech
Superheat ______Tech

Head pressure _______Tech
SCT – Gage - Saturated Condensing Temp _______Tech
Small Liquid line - temperature: _______You
Subcooling: _______
Return Air temp DB &, WB or %RH: _______You
Supply Air temp DB &, WB or %RH: _______You

With the information data below and an accurate Cubic Feet per Minute (CFM) airflow, I can ball-park the Units BTUH output
Return Air temp DB &, WB or %RH: ____ ____You
Supply Air temp DB &, WB or %RH: ____ ____You
Take a cotton cloth & wet with room temperature water, wrap it around the thermometer & use it for the wet bulb temps above.

Except for the Pressures, Superheat & subcooling you can take most of the other Temp readings for me.

My advice: to every user, get a low cost humidity gage at a local hardware store & see what the percentage-RH is in your home, I can cross-reference that to the wet bulb depression so you could use the humidity gage instead of wet or use both.

If you want to save money you will take the time when it is hot & warm in the house to take all this temperature data!

Please Respond, ASAP.

Anyone is welcome to use the Data Collection for use as they see fit!

“Copy only the data portions & paste in your Word-Processor, make a couple hard-copies, then send me what you take, & get as much of this data as your Tech will provide for you.”

My monthly electric bills run $50.00 or less, & I keep very cool, in a 1937 farm home, even in 104-F Heat Index!

Are your electric bills too high?

udarrell - Darrell, Retired HVAC from mid 1970’s

Gurgling Pulsating Sounds at TXV: Low evaporator heat-loads lead to reduced liquid line mass and increased evaporator mass could be due to airflow problems. Eliminate low evaporator heat-loads before looking into adjusting the refrigerant charge.  Gurgling and pulsation noises at the expansion device can be caused by low evaporator circuit heat-loads, low charge, and/or non-condensibles and moisture in the system. Unbalanced airflow through the various distributor circuits of the evaporator coil will cause the TEV to close down refrigerant flow starving the coil. Piston-flow-rators will make it impossible to properly charge the system and cooling will be greatly compromised unless you eliminate the cause! "Put your ear on the liquid line at the evaporator coil."

On every Rheem condenser cover it lists "non-condensibles and or moisture" as causes for a gurgling or pulsating noise at the expansion device. The entire evaporator circuits, may not become active for various reasons, - "the entire coil must become fully active for efficient performance."
The purpose of these recommendations is to provide liquid refrigerant at the expansion device and provide efficient operation. Hopefully, this will aid your research.  If I can be of additional assistance, contact me.

Too many do not properly purge & evacuate contaminated central air conditioning systems.

The Triple Evacuation Method is normally done on refrigeration systems, R-410a systems require it on central air conditioning systems:

First, remove any valve cores with a special  valve core remover this will speed up the evacuation time. Back service valves two turns off their back seat.

1) Re-claim unit charge (Recover all the refrigerant)

2) Charge system to 150 PSIG with dry nitrogen and leak test

3) On contaminated systems replace the filter dryers. Then Repair all leak(s)

4) Evacuate system to 500 microns valve off & see if it holds 500 microns for ten minutes, if it holds, break the vacuum with dry nitrogen

5) Evacuate system to a deeper 400 microns, valve off vac pump, & again break the vacuum with dry nitrogen

6) Evacuate system to 400 microns and & then Check to see if it holds. (Recharge with fresh clean refrigerant)

7) Check to see if the Supply and Return air ducts were correctly sized & sealed by the original installer.

If a vacuum pump will not evacuate a system below 1500 microns there is a problem with the pump itself, a leak in the system, or moisture in the system. Moisture is most likely because water vaporizes at 1500 microns.

Many HVAC contractors will consider this excessive time & effort for contaminated residential air conditioning systems, however it is a must for low temp applications.

The “micron” is a metric unit of measure for distance. The micron is a unit of linear measure; one micron equals 1/25,400ths of an inch. Modern high capacity vacuum pumps help speed up the evacuation process.

When a system has been evacuated below 500 microns, the pump is valved-off with the micron gauge connected, if the vacuum rises to 1500 microns and stops, there is moisture remaining in the system. If it rises above 1500 microns & continues to rise there is a leak. You should allow at least 15 minutes after the pump has been shut off an accurate micron gauge reading. When a system will not evacuate below 1500 microns there is either a lot of water or there is a system leak.

http://www.udarrell.com/air_return_latent_condenser_split.jpg  Click this Important Graph
Page 618, Refrigeration & Air-Conditioning (ARI) Second Edition, C 1987
Those lower SEER units had higher condenser splits than 12-SEER and higher units.
Sorry, I defiled the graph, 90-db outdoor, 80-db indoors with 67 wet bulb/50% RH represents the condenser splits shown above.

The condenser fan speeds are slower on several of the 10-SEER Tonnage Models.
We are only trying to get a figure to go by for a comparison. When new condensers and Evaporator coils "are installed on older air handlers" the new, or old, evaporator coils are usually under heat-loaded. (Always, check voltage and amp draw!)

The Base Spec sheets 12-SEER part no. 421 41 33301 03, Feb 2001. These are the Comfortmaker units, which are nearly identical to Heil units. I used the first rating on each tonnage class. While the "Performance Cooling Data" is listed at a 95-F outside ambient temperature, you can adjust the indoor airflow to get the Nominal BTUH Rating at the customer's normal indoor stat' temp' setting and the most outside temperature/degree operating hours.

Click this Important Graph & Compare to the Condenser Graph
As the latent load goes up the indoor split goes down while the condenser split goes up.
Air Temperature Drop Through Evaporator Coil (1987 Period)
Indoor temperature and humidity load variations graph.
Refrigeration & Air-Conditioning (ARI) Second Edition,
Page 624, 1987

Below is an outstanding PDF "Basic AC Overview - Specifications VS. Reality"
by John Proctor, P.E., Proctor Engineering Group, LTD:

HVAC TECH PERFORMANCE RATINGS  "AC Specs vs Reality" PDF - It's Worth Your Time

Any of the HVAC companies I list on any of my web pages have nothing to do with the information I post on any of my Web pages nor do I guarantee its accuracy or assume any responsibility for how anyone uses that information.
All HVAC/R work should always be done by a licensed Contractor! This information is only placed on these pages for your understanding & communication with contractors & techs.

This information is for the edification of contractors and techs. I am NOT liable for your screw-ups, you are liable for what you do! - Darrell Udelhoven

Darrell's Refrigeration Heating and Air Conditioning - Federal Refrigerant Licensed - Retired Licensed Contracto

Air Conditioning System Trouble Shooting Superheat and Subcooling IMPORTANT !

Optimizing the Evaporator BTU/hr Heat-Input  Important!

 Determining Your Air Conditioner's Actual BTUH Output New- Surprises!
Optimizing Your Air Conditioner's EER and BTUH Output  Size it right then Optimize BTUH Output 

Air Conditioning Maximum Efficiency - Check-Up  Get your A/C optimized for efficiency 
Air Conditioning SEER Levels & Evaporator Air Flow   Losing 15 to 40% of SEER Rating?
Air Conditioning - Latent Heat Removal     Comfort-Zone Efficiency
Air-conditioning manufacturing companies - increasing the value of their heating and air-conditioning equipment to consumers
Best Practices Guide for residential HVAC retrofit
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Darrell Udelhoven
Empowerment Communications
Updated: 03/08/14