SEER Payback - SEER Ratings Nebulous - Use EER Ratings not SEER Ratings for Central Air Conditioners Test Delivered Performance after the Install

Manufacture SEER Ratings Payback after installs IS NOT being Accurately Represented or Reported to Consumers

- California Research Report on EER SEER  pdf - download 07/23/08
  - with Darrell Udelhoven - HVAC RETIRED - udarrell Home Plus HVAC Efficiency Overview Audio >Refers to my linked duct sizing pages Read this pdf explaining what Electric Power Companies are finally instituting: Verified Performance Get what U pay for!
Totally Free Load-Calc 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.
Affordable Test Instruments Techs Must Use  * Customers
 Simple A/C Check!
Video measuring airflow Velocity W/ anemometer on a Return Air grille
I'd use between to .50% & 55% for the free-air-area of a clean FILTER, & .90% factor for open grille area. 
He programmed it in, because when I did the math using .90% for the grille I got 336.57863-FPM Vel *X 2.376562-SF free-air-area= 799.9-CFM, or 2-Ton of airflow. 

*Basics Featuring the Testo 556 -*Video of a very thorough Air Conditioning BTUH performance test

The Testo 416 Airflow Test Checking airflow must be performed before charging a system

More Videos at bottom of this page |* HEAT PUMP DIAGNOSTICS

Optimizing EER and SEER Ratings

First, let us look at SEER Ratings.
The most important factors in seer ratings is the proper sizing of the equipment so that it reduces the number of run cycles per hour, per day and per season.

When a typical HVAC contractor quotes the efficiency of the Air Conditioning equipment SEER & Btu/hr and leads you to believe the new equipment will automatically deliver that efficiency & Btu/hr, think again. Typically, installed equipment only operates at 55% to 70% of rated capacity.

It is important to understand that "equipment ratings are only the potential efficiency of that component of the system under perfect conditions." Over half of the system’s efficiency depends on the efficiency of the ductwork system and quality of the field-installation.

There are some components that will it help elevate these seer ratings.
1.    First, is a variable speed and CFM control air handler.
2.    Second, is a same tonnage evaporator coil with a thermostatic expansion valve, both will help control humidity at 50% or less levels.
3.    Third, it is a room thermostat with an adjustable on/off set point differential up to 3
4.    Fourth, you could utilize a large 20-inch floor fan to circulate the air when the unit is off, or even when it's on.

SEER Payback needs to be Properly Represented to Consumers!

  The SEER Ratings are too nebulous & do not translate to the specific application conditions that each consumer will normally have in their homes. EER is simpler & more reliable when the systems are correctly sized to the load.

 From 2008 AHRI Standard 210/240 Performance Rating of Unitary Air Conditioning and Air Source Heat Pump Equipment:

  Pages 89 and 90:

 SEER calc for a single speed compressor w/fixed speed indoor fan:

  SEER = EER (at 82°F ambient) x PLF (.5)

  Where PLF (.5) = Partial Load Factor = 1 - (.5 x Cd) where Cd is the Cyclic Degradation Coefficient.

 Basically, it's the EER at 82°F ambient, 80°F indoors adjusted by fudge factors.

  Pages 89 - 94:

 SEER calculation for a single speed compressor and variable speed indoor fan:

  SEER = EER over a weighted average range of outdoor "bin" temperatures x fudge factors.

  The outdoor bin temps and their weighted averages are as follows:









 Total = 100%

 Note that the 3 lowest outdoor ambient temps (67°F, 72°F, and 77°F) make up over 66% of the value of the SEER calculation.

The SEER of a system is determined by multiplying the steady state energy efficiency ratio (EER) but measured at conditions of 82°F outdoor temperature, indoor 80°F Dry Bulb and 67°F (about 50% RH indoors) Wet Bulb indoor entering air temperature by the Part Load Factor (PLF) of the system. (The PLF is supplied by the government.) 

You would also have to operate your A/C at those percentages of outdoor bin temperatures to make the SEER rating have any real relevancy. IMO; SEER ratings are a lot of irrelevant paperwork potential more attention to EER that you can post install test & verify. When condensing units are 'slightly' undersized, the EER is better & more relevant.

The SEER Rating is 'at a particular set of conditions' that are NOT typical design conditions, or at your particular climate zone and home's conditions.

Summer Outdoor Design varies however, we usually design for 75°F indoors NOT 80°F, also when systems' are downsized properly to achieve long runtimes the Part Load Factor becomes far less of a factor. Always go by the EER Rating NOT the SEER rating because, as the SEER goes higher the EER ratio to it drops. Therefore, when the system is sized properly you have a lot more steady-state continuous runtime cycles & the PLF will be minimized.

Well, that is misleading because the PLF figures in, -the cyclical start-ups, whereby it takes 5 to 7 minutes to reach full operating capacity. In many climate areas there is an advantage to slightly Btu/hr under-sizing the A/C system, as there are very few seasonal hours that you need Btu/hr ratings that are called for by using the existing over-capacity sizing methods.

"During average operating conditions in its particular environment, I want to peak-load the evaporator at near its Btu/hr Rating." This is where a fully controllable variable speed air handler comes into play, toward keeping the evaporator near peak load conditions.

Therefore, to optimize your air conditioning system the contractor’s Tech would need to effectively incorporate all the above component factors to optimize the EER and the SEER of your air conditioning system.
 - Darrell Udelhoven

SEER Payback needs to be Properly Represented to Consumers

First, consider EER:
ARI introduced the Energy Efficiency Ratio (EER) in 1975. This was an HVAC industry instituted way to determine the relative efficiencies of one unit to another in the cooling mode. EER was determined by dividing the published steady state capacity by the published steady state power input at 80°F dB & 67°F Wb indoor and 95°F dB outdoor.

Consider the criteria being used for their EER formulas.
Air conditioner EER ratings, and BTUH Tons of Cooling Capacity ratings on Air Conditioning units are rated at an outdoor temperature of 95°F, and an indoor 80ºF dB 67ºF WB or, a 50% Relative Humidity.

SEER - The Seasonal Energy Efficiency Ratio is a standard method of rating air conditioners based on three tests. All three tests are run at 80°F inside and 82°F outside. The first test is run with humid indoor conditions, the second with dry indoor conditions, and the third with dry conditions cycling the air conditioner on for 6 minutes and off for 24 minutes. The published SEER will not represent the actual seasonal energy efficiency of an air conditioner in your climate and your other environmental and system factors.

Quoting Tescor: Psychrometric Test Rooms are used by air conditioner manufacturers to determine the thermal performance of unitary air conditioners and split systems. Tescor utilizes dual rooms (indoor and outdoor) and the air enthalpy method to determine unit capacities and provide heat balances. Code testers, which include AMCA nozzles, provide accurate determination of the test unit air flows and outlet air conditions. Tescor’s control software allows the user to perform all of the ARI standard tests including the capability to perform SEER and HSPF calculations:

Add to this the Part Load Factor (PLF):
The SEER of a system is determined by multiplying the steady state energy efficiency ratio (EER) measured at conditions of 82°F outdoor temperature, 80°F dB/ 67°F wb 50% RH indoor entering air temperature by the “Part Load Factor” (PLF) of the system.
The PLF is a measure of the cyclic performance (CD) of a system and is calculated as follows: CD is Cyclical Data
PLF    = 1.00 -  (CD X's 0.5)

cyclic performance (CD) value in the above equation has been determined by the government to be 0.25." The government contends that the PLF should equal: 
[1.00  -  (.25 x .5)] = .125
1.00 - .125 = 0.875, which yields: PLF  of 0.875
A 3-ton system would be 36000 X's PLF .875 = 31500-btu/hr, or closer to 2.5-ton 30000-btu/hr system.
A 4-ton system 48000-btuh X's .875 = 42000-btuh or a 3.5-ton PLF operating system
Relationship of SEER to EER and COP
SEER is related to the Energy Efficiency Ratio (EER) and also to the coefficient of performance (COP) commonly used in thermodynamics. COP is a measure of efficiency. The COP of a heat pump is determined by dividing the energy output of the heat pump by the electrical energy needed to run the heat pump.

The higher the COP, the more efficient the heat pump. For example resistive heat has a COP = 1. The EER is the efficiency rating for the equipment "at a particular pair of external and internal temperatures," ---

"while SEER is calculated over a range of 'expected external temperatures' (i.e., the temperature distribution for the geographical location of the SEER test). [Real tricky nebulous temp & humidity expectations or assumptions! - udarrell]

Formulas for the approximate conversion between SEER and EER or COP in California are: [2]

SEER = EER ÷ 0.9
SEER = COP x 3.792
EER = COP x 3.413
From equation (2) above, a SEER of 13 is approximately equivalent to a COP of 3.43, which means that 3.43 units of heat energy are removed from indoors per unit of work energy used to run the heat pump.

The relationship between SEER and EER is relative depending on where you live because equipment performance is dependent of air temperatures, humidities, and pressures.

The relationship stated above is typical if you live in the lower-elevation portions of California; however, if you live in the higher humidity of Georgia, it is better approximated by:

SEER = EER ÷ 0.80
due to the much higher humidities. A similar relationship exists in relating SEER and COP, also depending on where you live.

If you over pay for over capacity equipment, -- you will be paying more every month and will not be as comfortable as you would sizing it right to also achieve the appropriate humidity levels!

7 EER or less
10 EER
12 EER
13 EERApprox.'
Approx.''Max' condenser air temp 'delta-T'
ave. less
Approx. 'Max temp drop 'across' E-Coil
ave. more
ave. more
Approx.'Max' SA/Return Entering Air 'Delta-T'
The Supply Air & the Entering Return Air delta-T, - tends towards less & less as the EER goes higher,
therefore, dehumidification could become more difficult at the highest EER levels. The EER & SEER levels widen, as SEER sky rockets.

When a typical HVAC contractor quotes the efficiency of the Air Conditioning equipment's SEER & Btu/hr, and leads you to believe the new equipment will automatically deliver that SEER efficiency & Btu/hr rating, think again. Typically, --installed equipment only operates at 55% to 70% of rated capacity. Oversized equipment is the worst combination there is because the duct system airflow and heatload on the cooling coil are often way off what is required!

Equipment Ratings are only the 'potential efficiency' of that component of the system under perfect conditions." Over half of the system's efficiency depends on correct equipment sizing toward adequate run-time, on the duct system sizing, i.e., on the quality of the complete field-installation!

What you want & need is right sized equipment operating at its optimal ratings within varying conditions, for your optimal comfort and savings.

If all contractor's would do the above, coupled with installing equipment sized according Manual J loads (with no safety factor), along with Manual S selection procedures, comfort would go up, humidity control would improve, and installation and operating costs would be much lower.

Utility demand loads could be cut by at least a third, or even up to a half. Energy loads would be significantly reduced, reducing our nation's energy usage. The return on the time and effort invested on this higher quality level of work would be tremendous - for customers, the community and the nation.

Unfortunately, most HVAC contractors don't use these procedures to size equipment and design duct systems. It's estimated that only 10% of heating and cooling equipment sizing decisions are based on some type of Manual J calculation and that less than 1% of the jobs are based on an aggressive accurate implementation of these recommended design procedures.

Many if not most contractors are designing new and replacement systems that feature oversized equipment, "improperly sized supply outlets" and duct runs that are too small, too leaky and inadequately insulated.

The Manual J gives appropriate answers if you use an “aggressive” set of assumptions. However, most HVAC contractors tend to skew input data to make the calculations match their favorite rules of thumb. Follow the manual J rules and you will get a reasonable margin of safety. However, after skewing the numbers, many contractors throw in an extra half ton or more of A/C to feel safe. No wonder a large percentage of equipment is considerably oversized. Also, the airflow is usually so compromised on the oversized units that it isn't putting out many more btuh than properly sized equipment would be, but it's an energy waster and is costing and arm and leg to operate.

Especially if your system is oversized or there are a lot of low AC load days use an adjustable differential room TH.
TH Differential
: Differential is defined as the difference between the cut-in and cut-out points as measured at the thermostat under specified operating conditions. For example, if the thermostat turns the COOLING EQUIPMENT ON AT 78-F & OFF at 76-F that is a 2 degree differential setting; heating equipment on at 70 degrees F and turns the heating equipment off at 74 degrees F, then the differential is 4 degrees F. Some have half degree increment settings over several degrees of differential spread.

I want a room TH (with NO cooling anticipator) that I can set within the "Human Comfort Range" to kick-in at say 78
°F and off at say, 75°F - that would result in longer run-time cycles. The result would be a big improvement in dehumidification, improved efficiency plus longer equipment & component life.

Combined with a 3-degree differential, there is a need for very low cost air circulation at the location of the occupants.  That is a way to boost SEER, reduce utility bills & provide adequate "Human Comfort Levels

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

Design Engineering and Installation Objectives should be focused towards achieving the most efficient and effective means toward  a conditioned space that is within the "Human Comfort Zone, and within an affordable investment 'payback' period."   

Summer Comfort Zone

Relative Humidity

Maximum Comfortable Temperature

Minimum Comfortable Temperature













The above comfort zone was found to be acceptable to 90% of test subjects drawn from a range of age groups and genders, with work and life-styles involving varying levels of activity and clothing. An air conditioning system that establishes and maintains indoor conditions within this zone will provide thermal comfort. It will produce a neutral sensation, occupants will feel neither too hot nor too cold. Above chart and findings From: Home Energy Magazine Online September/October 1996) Sizing Air Conditioners: If Bigger Is Not Better, What Is?  by John Proctor and Peggy Albright

The proper system sizing for long runtimes along with a computerized variable speed blower to keep the heatload up near the evaporator's rated capacity would reduce the EER & SEER ratio!

That is why if you live in a dry climate like Dallas TX or in Arizona I would us at least 450-cfm per ton through a wet cooling coil and measure the BTU/hr output of the condenser.
Condenser Gross BTU/hr = condenser temp = CFM X's Temp/split X's  1.08
Motor Btu/hr =Volts times Amps (or) Watts X's  (PF) Power Factor of 0.90 X's 3.413 converting watts to Btu's (Indoor blower motor to) = Net Btu/hr Output.

The condenser and compressor will both handle overloads when conditions exceed your average seasonal heatloads. High efficiency, variable speed blower motors, along with TEV refrigerant controls could help reduce those higher heatload periods.

Some of the high SEER units do not look so great when you figure their EER.
However, when selecting A/C equipment between EER Verses SEER:
"How many hours (yes hours) your area spends close (or above a 60% duty cycle) to OD design temp, determines which rating method you should use." - Beenthere
Maytag and other companies now have some of the computerized engineering I have been talking about:

Paired with a SignatureStat™ this control combines the functions of a humidistat and thermostat into a single device. Simple menu-driven programming helps you control your energy costs and comfort.
   - udarrell    - Darrell

Specific condenser equipment Information such as this older graph "updated" with both the Wet Bulb (WB) and the associated Relative Humidity (RH) along with the condenser split at say 90 or 95 outdoor ambient temperature.

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 very 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. (A 0.80 factor could be close.) Some of the 10-SEER temp-split figures need correcting, will do ASAP. Most Splits rounded off.

CONDENSER TEMP-SPLITS - Comfortmaker® 12-SEER units - I used 0.80 Motor Power Factor

1.5 Ton 18,400  21°F Split    Cond. CFM 1400 WATTS 2222 1.5-Ton is from actual published DATA - ARI Rating Conditions
2-Ton    24,800  24°F Temp-S Cond. CFM 1400 WATTS 2659
2.5-T    30,200  21°F Temp-S Cond. CFM 2000 WATTS 3404
3-Ton   35,600  18°F Temp-S Cond. CFM 2800 WATTS 4117
3.5 T    42,500  21°F Temp-S Cond. CFM 2800 WATTS 4554
4-Ton   48,500  19.5°FSplit Cond. CFM 3400 WATTS 4761
5-Ton   59,000  25°F Temp-S Cond. CFM 3400 WATTS 6969
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, 95°F-db outdoor, 80°F-db indoors with 67 wet bulb/50% RH represents the condenser splits shown above.

Typical matched units from major manufacturers have Sensible Heat Ratios (SHR) in the 68% to 80% range (or 32% to 20% Latent) when it is 95-F outside and 75-F with 50% relative humidity inside. Proper mixing of the air and proper distribution to individual rooms is critical for comfort.

All air-handler equipment should have capped ports for taking static pressures with information on how to do it along with a line graph or other information of the blower performance at various static pressures.

These are added value features that can be used in all advertising and marketing, providing your company with a distinct value advantage to all potential customers.

All of the above information should be easily accessed on the Internet for the convenience of techs and equipment owners.

Air-conditioning contractors could make up sticker graphs showing how to check the capacity of the A/C they bought from you. It's a "Value Added Feature," you could promote to even your potential customers, they will appreciate you doing that for them.

Better Cooperation by manufacturers' toward, distributors, HVAC/R Contractors, Techs, and all consumers of their equipment would make performance evaluation simple and easy to perform.

The motor vehicle techs have the dynamometer to evaluate the delivered horsepower of the motor under various loads and conditions.

HVAC/R techs and consumers have NO easy way provided to evaluate the varying load BTU/hr performance of an air conditioner evaporator and condenser design combination.

Let us say it is getting the design optimal-load on the evaporator and condenser however, the run-time is much too long for the A/C unit's design and the design cooling heat-load, --where do we look next?

We look at the supply-air (SA) and (RA) return air-ducting system for design and installation problems.

Many Return Air systems set the furnace on top of a RA chamber that is not sealed off from hot attic air —which overloads the cooling coil. This is also very dangerous, as the RA suction will put a negative pressure on the combustion-air venting and could easily result in carbon monoxide poisoning and death!

In most homes there is NO Return Air ducting to the various rooms. When the system pressurizes a bedroom, this positive pressure forces the conditioned air out through any opening in the room to the outdoors. Building science research states that for every cubic foot of air forced out of a building, a cubic foot of air infiltration must be drawn in from outside to replace it.

Therefore, when air is forced out of a room under pressure an equal amount of air is drawn into the main body of the home to replace the air forced-out. Depending on the number of doors that are closed, the rate at which hot or cold outside air enters the home goes up by from say, 300% to 900%. In turn, utility bills go up, comfort goes down, and health problems may ensue.

In a four-bedroom home with all of the doors closed & with a large 2000-cfm airhandler, it could be drawing in almost 1,000-cfm of outdoor air! "With a high outside humidity and/or temperature difference, the air-conditioner will never catch up to the added heat-load."

To allow for cooling mode Return Air, the "upper panel of a door can be removed and an upward louvered wooden or metal grille can be installed." Alternatively, make a grilled opening of the proper size through the wall near the ceiling.

The Case for (TXV) Thermostatic Expansion Valve Refrigerant Controls & Higher SEER Ratings

TXV's give a colder coil than (Flow-rator) pistons under the same conditions and get colder faster.  I have a data logger that has two external temperature probes. I put one before the coil and one after the coil.  I start the data logger, then turn the AC on.  The TXV gets 18 to 22 degrees across the coil in 5 minutes and 80% of that in 1 to 1.5 minutes.

The piston gets
16 to 18 degrees in 10 minutes and 80% of that in 5 minutes.  Under part load conditions the TXV will dehumidify better.  Most systems run most of the time under part load conditions.  Guess what?  I am going to install TXV's most of the time, just to cover my back side. - Stretch | 4/28/05 (NG)
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 charge, and/or non-condensibles and moisture in the system. Unbalanced airflow through the various distributor circuits of the evaporator coil will cause the TXV to close down refrigerant flow starving the coil; while Piston-Flow-Rators will make it impossible to properly charge the system and cooling will be greatly compromised unless you eliminate the cause! "Cup your ear to the liquid line at the evaporator coil., & listen." You can hear some of them pulsating 10 feet away.

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 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 300 microns, valve off vac pump, & again break the vacuum with dry nitrogen

6) Evacuate system to 300 microns and charge unit (Recharge with fresh clean refrigerant)

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

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.

Deeper evacuations are very important for Refrigeration Systems, Air Conditioner's are somewhat less critical.

Air Temperature Drop Through Evaporator Coil (1987 Period)
Indoor temperature and humidity load variations graph.
Refrigeration & Air-Conditioning (ARI) Second Edition,
Page 624, © 1987
Getting it right makes all the difference in the world.

Darrell's Refrigeration Heating and Air Conditioning - Retired 

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

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Posted: 04/20/05; Last Edited: 04/17/14