Wisdom Principled Empowerment Communications
& People Empowerment Broadcasting

- with Darrell Udelhoven Pic of udarrell HVAC Contractor & Technician since mid-1970's - Retired
Publisher of the Series - The Real Political Issues & People Empowerment Broadcasting

- with Darrell Udelhoven Edited 03/08/14

Go to for several easy ways to ballpark Home & equipment BTU/HR Performance

Best ROI Home Investment or Lose the Investment money annually "Home Energy Efficiency Pays You BIG." Video
Read this pdf explaining what Electric Power Companies are finally instituting: Verified Performance Get what U pay for!

It is summertime and time for you to do an easy safe simple check on the performance of your air-conditioning system.

 First, make sure the return air filter is clean, and then you will need a digital probe thermometer and a low cost percent relative humidity gauge to check the indoor humidity level.

 If you have an air conditioner that was manufactured between 1992 and 2005 it will be a 10 to 12 SEER R-22 refrigerant unit.

hen the temperature reaches 85 outdoors and the indoor temperature is 80F and the relative humidity indoors is right around 50% RH the outdoor condenser temperature split above the outdoor temperature should be around 20 to 21F or around 105F.

If the indoor temperature is 75 and the relative humidity is 50% then the air discharge temp-split off the condenser should be 17F or 102F off condenser.

The indoor temperature split between the return-air at the supply air grille closest to the air handler should be a 19 to 21F temperature drop with either an 80F or 75F indoor temperature. This is also the indoor split with the higher SEER units at 13 SEER or above.

If the indoor temperature split is too high may have very low airflow which needs to be brought up to its normal CFM Rate.

If the outdoor condenser split is too high your air handler may be drawing hot air into the return from the attic causing the high condenser discharge air temperature.

If the temps are within plus or minus a degree or two, that air-conditioner is performing fairly well.

On the new air-conditioning systems at 13 SEER & higher the outdoor condenser split is much lower than it is on the 10 to 12 SEER units; the indoor temp-split is the same.

Far too many HVAC service persons do not check the actual delivered performance of the system; the actual delivered performance of all air-conditioning systems should be checked with a permanent record left at the air handler in the home.

This program series is on Fox channel 47 in Madison...should be on public TV. The SEER Savings Chart is however misleading.

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. 
70% of homes in California are operating at 50% capacity. - California Energy Commission (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...
We could reduce existing residential heating Btu per hour SIZING by around an average of 50% and cooling equipment SIZING in America by 30% to 40% or more if Contractor's would perform honest Manual J calculations and provided full credit for every load reducing element or detail they can when doing the calculation audit.
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...

Free online load-calc - Print when you get the sizing right with the retro-work that's needed.
Additionally, load reduction remedial actions should always be provided as options toward further reducing Air Conditioning and heating equipment sizing.

Some easy simple ways for anyone to check the performance of their air-conditioning system

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 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 you 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 you 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: _______ = _______ 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 WITH (TWO), Half-Ton Window A/Cs & basement large dehumidifier:

Summer, June 30, 2012; Darrell’s meter; 62610 – 62140= used 470-KWh * .0985= $46.295
New 95% propane furnace using only 20,000-Btuh per hour during cold SW WI nights at around 10-F


  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


HVAC TALK   #1 Residential Forum - HVAC Talk Click my image & contact me there with your numbers!

Excellent Illustrated Ways to Save Energy.pdf Save with/in Adobe Reader
*Some utility companies will cut rates in nearly half for electric heating, should for heat pumps, too.
HVAC Efficiency Overview
My Audio overview; listen while you do other things

Save Tons of costly Energy when washing & Drying Clothes, etc. Possibly Cut Utility Bills in Half
*Selecting Air Filters - Sizing the Filtering Area - Critically important!
Money for mortgage payments.
Cynergy Home HVAC Energy Rater Audits BR Audio
Why Home Energy Efficiency Auditing is important to our future Jeremy Rifkin Video
Affordable Test Instruments Techs & home owners need & can use
Excellent Public Radio Program Above - Listen & Learn While Reading!
It is critical for Broadcast media to launch an all out PSA campaign to Cut Home Energy use in Half; that will also lead to lower energy prices. This is the low energy cost way, Not Cap&Trade way- that could lead to high energy prices  & more unemployment & stagflation!

Natural Gas & electricity are used to dry clothes & heat water, Plus NG is used to generate a lot of electricity. Reducing its use, will reduce the remaining lowered heating use, per unit cost; a Win/Win Equation for everyone.

With mass media cooperation, it can become, ("IN the Public Interest"), a tremendous Mutual Win/Win on a global basis, plus it will greatly Reduce our carbon footprint pollution equation!

Buy indoor & outdoor clothes racks & pincher clothes pins, then dry clothes in a room in your home or hang in good weather on a line in your back yard; I never use my electric clothes dryer. It's easy to do & fun when you see how much money you will save!

Drying clothes indoors helps humidify your home in cold weather.

To remove wrinkles from a few fabrics, briefly use dryer's low heat wrinkle removal mode.

In warm weather if there is a code against outdoor clothes lines where you live, simple use your indoor clothes rack in a room with the windows open & a 20" Wind Machine vertical adjustment floor type fan blowing on the clothes.

Those blowers use about what a light bulb uses, compared to your dryer, that is nothing!

Wash clothes in cold water that you draw after the last washing, so it warms to room temperature.
Well prior to washing, put detergent in washer's cold water & cycle it for a very short time & agitate for a couple minutes, then shut off & leave stand for hours, then wash clothes & they will be super clean. I never use any hot water to wash clothes! Just these Two things with a family will save a ton of Energy & Money!

Heating water & using a clothes dryer are huge energy eaters; "if you do everything possible" you could drop your utility bills in half!

This is a good Quality Installation ACCA starter document:
Residential Quality Installation of Equipment - Check List
 Use to pre-qualify HVAC Contractors
Local PRO Contractor Locater Map Find These Forum Contractor PROs in your area
Audio about Govt Energy Auditors in NYC on CNN
Money for mortgage payments - Home Energy Rater Auditing Radio  Program.
I may do a few Home Energy Efficiency Audits starting in July 2011

Simple Ways To Check Your Air-Conditioner's Performance > Optimize It


To achieve optimal efficiency & the highest operating SEER Rating "longer run-times are essential."
It takes a lot of amps during startup, & it takes more than 8 minutes to reach efficient cooling performance.Now,there are RM THs that have half degree incrementals up to 3-F; e.g.,set at 78F-on 75-off = Higher Efficiency SEER Performance!

Everyone, get a low cost Testo Tester & ballpark figure actual BTUH & EER > information on tester:

Testo 605-H2 Fast Accurate Wet Bulb

Home Owners, very low cost anemometer to check airflow FPM Vel. & CFM, Info U Need:
I show how to convert readings to FPM VELOCITIES to CFM AIRFLOW.

Use the formula: register face velocity in FPM *X's register's area in sq.feet
6" rd metal duct 6*6=36*.7854=28.2744/144= 0.19635-sq.ft.
7" rd duct 7*7=49*.7854=38.4846/144= 0.2672541-sq.ft., etc.
You can look up on the Internet (Hart & Cooley & others') the supply air register/diffuser open area (Ak) sq.feet & use that! It is easy & simple for you to begin to greatly reduce a lot of wasted monthly utility expenditures!

Add together the number of branch runs to ballpark the actual CFM delivered to the rooms.
Air conditioners  & heat pumps need 400 to 450-CFM of airflow per-ton of cooling.
Get a low-cost Testo Tester & anemometer - ballpark CFM & ballpark figure actual delivered BTUH
Cut A/C cooling costs up-to 50% or more, read easy to do info below to easily check your A/C systems delivered performance! Do simple work on your home & lower cooling bills way down; it's on my pages!

*Basics Featuring BTUH Testo 556 *Video |< Examples for Techs; CK other Pages: Testo 550 Features

The information on Testo - easy checking wet bulb temperatures:
Testo 605-H2 Fast Accurate Wet Bulb
Everyone, very low-cost anemometer to get airflow FPM Velocities, get it:

Also, get a low-cost digital flat-headed pocket Thermometer to use flat on the piping; These instruments will PAY big returns!
You can pay for HVAC service, but may not get reliable servicing of your H-VAC system. That one incompetent service call expenditure would buy all the safe to use & easy to use test instruments you will ever need, to safely check your H-VAC system's "Actual BTUH Operating Performance." I don't know any local Techs that do it, or know how to do it!

YouTube Video -    Best:  

Installing  & Cooling Coil Best Practices NOT shown in above

  Install Best Practices Video:  needs to be at least +6" above an  , or large Oil HT/EX will greatly restrict ."
YouTube - How to   with Plastic Film-  Improvement  Do it RIGH

Simple to ballpark actual performance:
Duct system CFM X* 4.5 @sea-level, or use X* 4.35 if 1000' above sea-level, X* change in enthalpy = BTUH (Ballpark) Operating Performance. Home owners & anyone, it is easy & simple to do!
"U Must Right Click Link & open in New Tab," look-up wet bulb enthalpy figures on chart," & figure
change. I know of NO HVAC Tech that performs this easy test, that even you can do.
PRINT & USE the linked enthalpy chart below:

Wet Bulb Enthalpy Chart

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

Rules of Thumb for Duct Systems  - Hart&Cooley

Google search Hart & Cooley, also this pdf might help you select the right diffuser for the particular application, & list (Ak) free sq.ft., area of the diffusers:

A Major "Oil Furnace" Very Low Airflow Problem - Requires Fixing
Regal & Hallmark & nearly all Oil Furnaces - Installation manuals
Download the installation & service manuals
To find the information below; Use within the pdf search:  at least 6” above
Or use down arrow to P-8 & scroll down a-ways...
"If the oil furnace is used in connection with summer air conditioning the evaporator coil must be installed at least 6” above the oil furnace for proper airflow.
Distances less than 6” will result in decreased airflow."

Make sure outlet supply takeoffs are NOT blocked by the coil. In all cases, refer to the manufacturers’ data for static pressure losses to ensure the total system static pressure does not exceed 0.5” WC.

The North Country Oil furnace A/C or heat pump scenario:

Here is just one scenario; the small one story home with a basement requires only 14,000-BTUH of cooling but it has a 112,000-BTUH Oil furnace with a belt-drive quarter HP blower motor.

Three things have to be done right; first, the evaporator coil has to be sized to flow at least 1250-cfm that requires a 3-ton coil.

Second, the evaporator coil has to be mounted at least 6” above the Oil furnace to eliminate an airflow restriction between it and the super large heat exchanger near the top of the furnace.

Third, the belt drive motor has to be replaced by a multi-speed direct-drive blower motor that will deliver the correct 1250-cfm for heating & 600 to 675-cfm airflow for cooling.

I have witnessed a 2-ton evaporator coil being installed directly on top of the Oil furnace & the quarter HP direct drive motor left in place.

Can you cite the horrendous problems this creates?

Think through what you’re doing & the consequences before doing it!

Required fan motor HP varies as to the cube of the rpm blower speed.

Also, at 700-rpm & .2" SP for heating my Thermo Pride OL 11 with its belt-drive quarter Hp motor will deliver 1200-CFM;  add a cooling coil, & at .5 SP it will deliver only 400-CFM.

Keeping the total static pressure as low as possible and within mfg'ers ESP requirements for air conditioning is the first requirement in an efficient system design. 

BTW, what is the average pressure drop across the new +90 high efficiency furnace condensers? That pressure drop should be published by all of the companies!

My Scan of My ThermoPride OL 11 Graphed Blower-Curve-Chart
Thermopride OL 11 Graph ipg image - Thank you Dave Staso, CA. for the better expandable image!
"After it loads Right click "Show Original Images" - Move cursor arrow over graph - Click + when 'over graph' for expanded image," then print on the highest quality setting.


In summer, Air conditioner & heat pump user's, this is a "Simple Easy Safe Way" to Check an A/C's Thermostatic Expansion Valve  (TXV) metering system's refrigerant charge & any A/C's  Performance:
Record the outdoor temperature, then "Take a thermometer & check the air temperature coming off the outdoor condenser."

A higher indoor humidity raises the condenser temp-split, lower humidity lowers the condenser temp-split.

Depending on the units SEER Rating; all data, AIRFLOW @ 450-CFM per-ton of cooling, Room temps 75 to 80-F,
at 50% indoor relative humidity, the temp-rise for a 12-SEER condenser, should be between around 18 & 20-F; much below that split could be unacceptable.
A 10-SEER, at above conditions, 22 to 24-F Condensing Temp-rise
(CT) above outdoor temperature.

A 14-SEER, R-22, 1.5-Ton, Indoor airflow @ 675-CFM, Rooms 75-F @ 50% relative humidity; CT  rise 14-F.
A 16-SEER, R410A, 2-Ton, @ 900-CFM,
Rooms 75-F @ 50% relative humidity; CT  rise 14-F.

Locate the small uninsulated copper line where it makes a bend, outdoors or indoors, so you can put a digital thermometer flat on it & insulate the TH with something (piece of the tubing insulation) read the temperature & subtract it from the outdoor condenser discharge air temp.

E.g., condenser temp 110, line temp 100-F that is 10-F subcooling & 10 to 12-F is a normally charge system. If it's considerably less than 10-F it could be low on refrigerant or need a Tech to check it; too far above 12-F it's overcharged, call a Tech, could also be a restriction in the lines.

A TXV coil will usually show a 9 to 12-F superheat .

The subcooling (BallPark) should be between 10 & 15-F on either a TXV or fixed orifice metered system.

You should own a low cost digital pocket thermometer:
Now the reality is that you don't need a manifold gauge, - anyone can Ballpark check the charge in respect to the indoor airflow with only a little low cost MA-Line digital thermometer using some tubing insulation on the sensor probe. An A/C supply Outlet might sell you one or inquire at hardware stores! Saves money on needless A/C Service Calls!

Take the outdoor temperature & subtract it from the outdoor condenser's discharge air temperature.
This temperature is standard for different SEER Rated units.

A 12-SEER unit, with 50% relative humidity indoors will have ballpark, will have an 18 to 20-F temp split
A 14-SEER will be around a 14 to 16-F temp/split. if too far above or below those temps, call for an A/C Tech.

Identifying your registers/diffusers & their (Ak) sq.ft. area, so you can multiply the FPM Velocity times the Ak to get the (CFM) Cubic Feet per Minute airflow from that register.
Click on the categories to see the diffusers & Return-Air Grilles then find them on your downloaded pdf's engineering data.
Hart & Cooley:
Do a lot of Hart & Cooley engineering data searches, look at the registers & the Ak sq.ft. data to figure register's delivered CFM.
Home Energy Magazine Online September/October 1993 
Raising Standards and Savings
New Group Hunts Bad Ducts (A/C duct systems)

Does 40 billion kWh sound like a lot of energy? How about 4 billion therms? Researchers believe that's how much electrical and gas energy this country "could save by fixing inefficient ducts using current techniques." "Refining those techniques could reap savings of 90 billion kWh"plus 9 billion therms! Peak loads would be reduced too. To pursue these tremendous savings, national, state, and utility research laboratories, the U.S. Department of Energy, utilities, and energy service companies are collaborating. Their consortium is called "Residential Energy Efficient Distribution Systems," or REEDS.

These techniques, along with reducing air infiltration & heatgain/heatloss calcs, ought to be taught in all our schools as part of the Science & math curricula. Half the heatgain/heatloss can be due to a high Home Air Infiltration Rates!
ASHRAE standard 62-1989 is 0.35 ACH (Air changes per Hour) or 3-hours for a total interior, Air INFILTRATION Change.
Home Air Infiltration
Air Infiltration sources DTI Corp Catalog
DTI Corp Air Infiltratrion
DOE Reducing Air Infiltration Information
May add more later.

Milwaukee Energy Efficiency (Me2)
The potential is great and the model is simple: The Milwaukee Energy Efficiency (Me2) program would allow building owners and occupants to pay for the cost of improvements as a charge on their municipal services bill or utility bill, on a schedule that allows them immediate savings.

If a participating building owner or occupant leaves the property before repayment is complete, the remaining obligation can go to the next owner or occupant as he or she benefits from reduced energy costs. The program will create thousands of good jobs — ranging from entry level to highly skilled — and fill them locally.  Milw. WI
If your monthly cooling bill is very high & you want to cut it in half or less; start with an entire home energy use & the HVAC Evaluation listed below.

Cut air infiltration to a minimum, a Blower-Door-Test will locate the air leak areas; a Duct Blaster to detect duct leaks & size ducts to optimize airflow.
Check for window options along with outdoor window shutters or awnings.

Half the heatgain/heatloss can be due to a high building air infiltration rate!
- Source Home Energy magazine online Sept/Oct 1993
- DOE Reducing Air Infiltration Information
The ductwork system & airflow must be accurately checked & optimized.
Refining those ductwork techniques could reap savings of 90 billion kWh" plus 9 billion therms!
- Source Home Energy magazine online Sept/Oct 1993
*To check your A/C system you need a thermometer, wet cotton cloth, or a humidity gage.
At a hardware store, it is around $10 for humidity gage & thermometer combo.
Keep the Temp/Humidity combo gage indoors.

Then check the condenser fins, they must be clean.
*** Absolutely Disconnect all the power 230-Volt breaker power to the condenser, including the furnace power for the low voltage in the condenser!

If you use water pressure, keep the stream in-line with the fins so it does not bend them.
Let it dry for a long time before operating for ten minutes or longer, then take the temperature readings.
Let it dry out for several hours before reapplying power &/or using the A/C.

The A/C user need not know all the tech info, all they need to know are a very few basic simple ways to identify that the system is not functioning correctly so if necessary you can call for a pro-tech to properly trouble shoot the system.

Now the reality is that you don't need a manifold gauge, - anyone can Ballpark check the charge in respect to the indoor airflow with only a little low cost MA-Line digital thermometer using some tubing insulation on the sensor probe. 
You can't order it there.

However First, you check the discharge air temp off the outdoor condenser, (that is the "Condensing Temperature (CT)," the higher the SEER Rating the lower the outdoor normal temp/split above the outdoor temperature will be.)
Then you either check the small liquid line tubing temp outdoors where there is a tubing bend, or indoors where it bends to enter the plenum. 

Indoors could be inaccurate as the tubing temp could vary higher or lower depending on temp conditions the line is conducting.

Subtract the small liquid line temp from the CT & you have the Subcooling temp which varies some from mfg'ers, but will be Ballpark 8 to 12-F Subcooled.

The condenser temp (CT) above the outdoor temp tells you how much indoor sensible & latent heat, & the 3 motor heats it is ejecting. The indoor humidity level has the biggest effect, the higher the humidity the higher the split.

Now, indoors the higher the humidity the lower the temp/split between Supply-Air & Return-Air.

At 50% indoor humidity the split should be Ballpark, around 18 - 20-F.

If blower wheel blades & all coils are relatively clean & the split is well above 20-F, you have low airflow with a low heatload through the evaporator coil.

If the indoor split is way below 18-F at 50% RH, you either have way too much airflow or some problems in the functioning refrigerant system.

To solve any of these problems you need to call a knowledgeable HVAC TECH! - Darrell U
Download these Energy Saving PDF Graphics  Ways to cut monthly Energy Bills, hopefully in HALF. Thanks for the link -  TEDKIDD

Look at the ducting, if it is not to code; make hard copies of this code & give it to whoever does the ducting work.
Make sure they get redo it right!
Never have flex duct interiors commercially cleaned, I just viewed Home Inspection photos showing the interior damaged & insulation plugging the duct.
Home Inspectors warn people because the duct cleaner's tell them it won't damage the ducts. Some HI's look into the boot areas for clues of problems...


On a normal temperature day & indoor temperature, check the humidity & temperature indoors & record it.

Then check the outdoor temperature, & the temperature of the condenser's discharge air.

Subtract the outdoor temperature from the discharge temperature to get the split.
Then you go by SEER Rating for the temp-split perimeters.

Try to check your A/C when conditions are 85 to 95 with indoor temps between 75 & 80-F, with around 50%RH.
Depending on indoor conditions, e.g., lighter loads; the split could be 2 to 3-F below the listed temperature.
All ARI Conditions 95-F out doors, 80-F indoors @ 50% RH (between 75 to 80-F is okay)

For 12-SEER Units=IndoorTemp-Split @400-CFM Per-Ton of Cooling 50% Relative Humidity|SA/RASplit |
18-F| CONDENSER TEMPERATURE SPLITS - Above Outdoor Temperature
1.5-Ton  18,000 Outdoor temp 95F; 80-F IDB, @ 67-F IWB or 50% RH; ARI Conditions = 21-F Condenser Air-Temp-Split.  Don's @10-F to 12-F Split - Low ID Airflow!
1.5-Ton 18,000 18-F to 21-F Temp-Split    Condenser CFM 1400
2-Ton  24,000  22-F T-Temp-Split  Condenser CFM 1400
2.5-T  30,200  20-F Temp-Split     Condenser CFM 2000
3-Ton  35,600 17-F Temp-Split     Condenser CFM 2800
3.5 T   42,000 18-F Temp-Split    Condenser CFM 2800
4-Ton  48,000 18 -F Temp-Split    Condenser CFM 3400
5-Ton  59,000 22-F Temp-Split     Condenser CFM 3400
CFM is Cubic Feet-per Minute of airflow through the condenser.

Goodman data for R-22, 14-SEER Units;
1.5-Ton 17,600-BTUH; 2.54-Ton evaporator coil, TXV; Single Stage:
Outdoor Temp 85-F; IDB 75-F; Humidity 52%; Indoor temp-split 19-F; Condenser Split 11-F; 675-CFM

Goodman data for R-410A, 16-SEER Units; 2-Ton 22,800-BTUH; 3-Ton evaporator coil, TXV; Single Stage:
OutdoorTemp 85-F;Indoor Dry Bulb 75-F;RH52%;14-F CondenserTemp-Split;IndoorTemp-split 21-F;800-CFM
----------------------------------------- Check your air conditioner:

Indoors:  Return Air Entering Temp: ____F  - Coldest Nearest A-Coil Supply Air temp: ____F  Temp-Split ______F   Relative Humidity ______%
Or, Wet Bulb Temp __F Outdoors: Outdoor condenser discharge Air Temp: _______F  - Outdoor /Temp ______F   Temp-Split ______F
On Oil Furnaces check the airflow, many have nearly half the airflow they need! Example; 100,000-Btuh Oil or Gas furnace needs 1300-cfm of airflow.

You can use a piece cotton cloth (etc.) soaked in room temp water. Set a hi-spd fan near the return air intake & wait until you get the lowest wet bulb temp. That's the Wet bulb temp & it's what I used to take with a sling-psychrometer. So, rig one up & just give me the wet bulb temp; wet bulb can also converted it to %RH.
Testo 605-H2 Fast Accurate Wet Bulb

*Video checking Static ESP 
Video 2 checking Static ESP View!Got DSL 11/2010

*Basics Featuring BTUH Testo 556 >Video Testo 550 Features

Copy above&use, it's FREE; You must link to this page or Cite Source To Tweet or publish this material:

---------------------------  E-mail me the data with CFM airflow & I'll give you its ballpark BTUH, or U can do it: udarrell**@**
This tells you the nominal amount of heat (BTUH) that is being absorbed by the indoor evaporator coil & being discharged by the outdoor condenser coil.

With outdoor & indoor coils clean with clean blower wheel blades & filter; If the outdoor condenser temp-split is low, & indoor
Return-Air temp minus Supply-Air temp is high, then there is NOT enough airflow heatload going through & being absorbed by the indoor coil.

If the condenser discharge air is within the nominal range, +/- 2-F, then the system is absorbing & transferring a nominal latent & sensible BTUH amount of heat from the interior of your home.

In this simple test procedure, the (1) Temperature-Split of Supply & Return Air, & (2) indoor humidity reading & the (3) outdoor condenser discharge air temp-split is all we need.

With the combination of the outdoor split & the indoor Supply-Air/Return-Air temperature splits & the room Relative Humidity Percentage, I can tell you if the indoor airflow is in the normal range.

Normal Supply-Air/Return-Air temp-split is 16 to 22-F. A heavy humidity load will take the split down toward 16-F. Dry air will have a high temp/split 22-F or a bit higher.

What can skew this test is a dirty indoor evaporator coil. In that event, the blower wheel blades will be dirty too, so with power off, check those blades!
Always do these temperature checks with a clean filter installed.

An airflow velocity meter, an anemometer, is a great instrument to have; they're not very expensive.
Formula for finding CFM Airflow
Quick method: The heat gain and Btu/hr of cooling is done for each room.
At 400-CFM per/ton of cooling, 12,000-BTUH / 400-cfm = 30-BTUH for each (CFM) Cubic Foot per Minute of Airflow.
At 450-CFM per/ton cooling use 12,000 / 450-cfm = 26.66-BTUH per each CFM, etc.

Then Select Supply duct size by CFM, velocity, & optimal Supply Air *(FR) Friction Rate.
A Room requires 3000-Btu/hr divided / by 30 equals 100-CFM, or around a 6" dia. RD metal duct.
You need-> Five duct runs for 1.5-ton unit, 18,000-BTUH: (Equal room loads,ha!) 18000 / 5-runs= 3600-BTUH / 30 = 120-CFM each 6" duct velocity 611-fpm Velocity. 18' length branch runs 611-fpm velocity at a Friction Rate 0.03" per 18'.

The total airflow should be in the range of 375 to 450-CFM per ton of cooling; Unless you have high humidity I'd go for 425 to 450-CFM per ton of cooling!
One ton is *(12,000-BTUH).

*Check the Return Air filter(s) often, need optimal airflow especially during a heat wave!
Cynergy Home HVAC Energy Rater Audits Iowa Public Radio Audio - Listen
Government initiated Energy Audits from CNN audio listen to while reading - Get CNN

Do Your Own Home Energy Audit Do infiltration On Windy days 

Wisconsin Office of Recovery and Reinvestment

Wisconsin Weatherization Assistance Program plus Audits

Iowa Weatherization Assistance Program
MI Weatherization Assistance Program
A Major "Oil Furnace" Airflow Problem Fix

This Air Flow problem is extremely important for sufficient performance!

Residential Quality Installation Check List Use - to pre-qualify H-VAC Contractors

TED Talk - Tim Jackson - "Economics Of Climate Change" - Your FUTURE
I've been advocating this for H.S. curriculum & as much as possible in all matter of mass media content.
I do NOT assume any responsibility for how anyone uses the information on my Web pages.

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 what you do, you are liable for what you do!  - Darrell Udelhoven

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


Please write me if you have anything you'd like to contribute! - Darrell 

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