Air Conditioning Contractors - Optimizing Efficiency

The critical importance of selecting the proper equipment components for your climate zone Anchor link

California Research Report on EER SEER  pdf - SEER Payback Savings cannot be accurately represented!
with Darrell Udelhoven (U-dl-hoven) - HVAC RETIRED - udarrell
TH Differential
Gurgling Pulsating Sounds at TXV  | CONDENSER TEMP SPLITS |

Air Conditioning Contractors Discussion of SEER Ratings - Latent Heat  -  Sensible Heat  Absorption Ratio Split
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Customers - Simple Check!

Best ROI Investment or Lose the Investment money annually "Home Energy Efficiency Pays You." Start with your home! Video

First, the "proper heat load sizing" of the entire air conditioning system to each room, including sizing ductwork to all rooms, should be done.

Free Load-Calc to help you check equipment sizing - print the results as you can't save the calc you've done!
On a home that has "not been" optimally weatherized, I’d use 0.7 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.

Using Goodman Manufacturing or other Expanded Cooling Data; e.g., using a 2-Ton 13-SEER, R410A, @75F 50%RH Indoors; "outdoor 90F," 'interpolate' between Charts 85F & 90F ambients, @800-CFM Mbh is 21.55, S/T is .765 * 21,550 is16,486-Btuh Sensible; 21,550 - 16,486 is 5,064 Latent. That's the simple close enough math...


*Video checking static ESP *Video 2 checking static ESP View! I Just Got DSL 11/2010 

Air Flow CFM of a very large Supply Air Register using a Testo 410 Vane Anemometer  Basic...

*Video measuring airflow Velocity W/ anemometer on a Return Air grille 
I'd use close to .50% for the free-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 Testing setup 2/26/11

Realtime HVAC A/C BTUH Performance Output (Part 1 of 2) YouTube Video

*Realtime HVAC A/C BTUH Performance Output (Part 2 of 2) YouTube Video

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New data show that Manual J indeed overestimates the sensible cooling load in hot, dry climates. It is likely that the same holds true in hot, moist climates. Proctor Engineering Group, the Electric Power Research Institute, Nevada Power, and Arizona Public Service monitored air conditioning systems installed in new homes in Phoenix, Arizona, and Las Vegas, Nevada. By testing the actual cooling capacity required to maintain comfort under severe conditions, these tests have yielded the first measurements that confirm and quantify the overestimation using the Manual J method.
Hourly sensible cooling load versus outdoor temperature monitored for a house in Phoenix, Arizona during an extraordinarily hot summer. Manual Joverestimated the Sensible (Thermometer measured heat) cooling load for this house by at least 50%. (Dry climate in Arizona = low latent/humidity factor) Even during this hot summer, an air conditioner sized to two-thirds of Manual J would have been more appropriate.

The critical importance of selecting the proper equipment components for your climate zone

It is essential to understand why the local weather environment dictates what SEER level air conditioning equipment you should choose.
In choosing equipment and its SEER level, it is important to understand the design engineering behind its functional capabilities.
First, when the engineers designed for higher Seer levels, they increased the volume and the BTU per hour capacity of the condenser coils and the evaporator coils; however, they reduced the BTU per hour capacity of the compressor.

The volumetric capacity of that smaller compressor depends on the absolute suction and discharge pressures under which the compressor is operating. The higher SEER units also have a much larger quantity of refrigerant charge than the older 10 & 12-SEER units had.

The lower volumetric capacity ratio of the compressor to the higher coil capacities only works well in an 82°F laboratory weather environment with a 50% relative humidity level,which is never a stable operating condition in the real world environment.

When you select the high Seer units in a climate where you have high outdoor sensible temperatures along with a high humidity, the temperature pressure ratio of the evaporator coil skyrockets as does the condenser coil pressures and temperatures, therefore the smaller capacity compressor in its relationship to the coils becomes overloaded.

Here comes the engineering caveat, if you are in a high temperature high humidity climate zone the evaporator pressure temperature ratio will be so high that there will be very little condensation of the moisture in the air. Additionally, always select an evaporator coil with a TXV thermostatic expansion valve refrigerant metering device as it will keep the coil colder at varying lower outdoor temperature conditions.

Also, buy a digital programmable room T stat that also has a cycles per hour (CPH) or a swing setting from 1 to 9 so you can reduce the number of short cycles while increasing the runtime of each cycle. This can really increase SEER performance & help a lot to control humidity problems in the summer cooling mode.

Additionally, the volumetric capacity of the smaller compressor will not be able to handle the increased volume of vapor. Added to this the condensing pressure will be much higher with also reduces the volumetric capacity of the compressor which is rated at less than the BTU per hour of both coils.

The higher SEER level you select above the 13 or 14-SEER levels the ratio between the lower BTU per hour capacity of the compressor compared to the evaporator and condenser coils becomes worse. Therefore, if you are located in a hot or, a hot and humid climate from an engineering standpoint and a performance standpoint, I do not believe it is a wise decision to go to extremely high SEER rated equipment.

There maybe rare exceptions to the above statements, if a variable speed compressor and variable speed blower motors are used. When these components are used, you should make sure that the contractor proves to you, before you buy the equipment, that the combination of components will work properly in your climate zone.
EER
7 EER or less
8 EER
9 EER
10 EER
12 EER
13 EER
'Max' condenser air temp 'delta-T'
30
27
24
15 to 25
14 to 24
ave. less
Max temp drop 'across' E-Coil
20
22
24
26
ave. more
ave. more
'Max' SA/Return Entering Air 'Delta-T'
35
32
29
27
ave. less
ave. less
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 you select the high Seer units in a climate where you have high outdoor sensible temperatures along with a high humidity, the temperature pressure ratio of the evaporator coil skyrockets as does the condenser coil pressures and temperatures, therefore the smaller capacity compressor in its relationship to the coils becomes overloaded. 
Here comes the engineering caveat, if you are in a high temperature high humidity climate zone the evaporator pressure temperature ratio will be so high that there will be very little condensation of the moisture in the air.
Additionally, the volumetric capacity of the smaller compressor will not be able to handle the increased volume of vapor. Added to this the condensing pressure will be much higher with also reduces the volumetric capacity of the compressor which is rated at less than the BTU per hour of both coils.
The higher SEER level you select above the 13 or 14-SEER levels the ratio between the lower BTU per hour capacity of the compressor compared to the evaporator and condenser coils becomes worse. Therefore, if you are located in a hot or, a hot and humid climate from an engineering standpoint and a performance standpoint, I do not believe it is a wise decision to go to extremely high SEER rated equipment. 
There maybe rare exceptions to the above statements, if a variable speed compressor and variable speed blower motors are used. When these components are used, you should make sure that the contractor proves to you, before you buy the equipment, that the combination of components will work properly in your climate zone.
Darrell Udelhoven

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At the most intensively monitored sites in the studies, we recorded air flow, temperature drop, and moisture removed from the conditioned air. The research team calculated the actual capacity delivered by the air conditioner for every air conditioner cycle.

Summer Comfort Zone.
Relative Humidity Maximum Comfortable Temperature Minimum Comfortable Temperature
60% 78.5oF  72.5oF
50% 79o 73oF
40% 79.5oF   73.5oF
30% 80oF 74oF
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 ASHRAE 55-2004 standard says 80-F at 55% RH would be comfortable; for me 76-F @ 55% RH is okay.
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First, before doing anything else check and thoroughly seal the entire ductwork!
You must know & record the operating feet per minute (FPM) velocity & the CFM to each room & the Total CFM airflow!

When the entire system is optimized for efficient full capacity
 operation,
it is better to slightly undersize than to over size equipment, this results in gains in run time and latent moisture removal. Short-cycling wastes energy in obvious ways, start-up uses extra power, it also takes 5 minutes or more for the unit to reach its full cooling capacity.

Very important for heating & cooling: Especially if your system is oversized or there are a lot of low AC load days use an Adjustable Differential Room T stat.
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 75-F that is a 3 degree differential setting; heating equipment,
On at 67 degrees F and turns the heating equipment off at 71 degrees F, then the differential is 4 degrees F. Some have half degree increment settings over several degrees of differential spread.
I have a LUXPRO PSP511LCa that has a swing setting that work perfect for achieving the temp differentials that are far more cycle efficient.

As you put more total heat-load through the evaporator coil, up to its capacity rating, both total capacity and efficiency increase for optimal Btu/hr, EER, and SEER.


air_return_latent_condenser_split.jpg (25707 bytes)
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.

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.
For the uninitiated, Delta-T is the difference between the air temperature entering and leaving the outdoor A/C condensing unit. This is a good diagnostic check because it measures the latent heat of condensation as well as the sensible heat absorbed by the vaporizing refrigerant in the indoor evaporator coil. I'm betting when you find out approximately how many BTUH that the AC system is actually transferring outside, you may be shocked. Many new Packaged Units have a very high condenser CFM airflow!
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. (A 0.80 factor could be close.)Some of the temp-split figures need correcting, will do ASAP. Most Splits rounded off.

CONDENSER TEMP-SPLITS - Comfortmaker® | Heil® | Temp Star® 12-SEER units - I used 0.80 Motor Power Factors

1.5-Ton 18,000  21-F Split       Cond. CFM 1400      WATTS 1536 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-F Split      Cond. CFM 3400      WATTS 4761
5-Ton  59,000  25-F Temp-S   Cond. CFM 3400     WATTS 6969

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.
Take the "listed watts" of the compressor and Condenser fan and multiply that wattage by 0.85 X's 3.413 to get the BTUH heat additive of the motor then add the listed BTUH of the condenser to it, and then divide by the condenser fan's CFM.
My late Brother Don’s 18,400-Btu/hr Heil® central A/C unit.
1400-cfm (outdoor) condenser *Xs 1.08 *Xs 12-F split = 18,144 minus 8,591-Btu/hr motor heat = 9,553-Btu/hr net Xs .80 sensible = 7,642 sensible 1,911 latent.
7642/1.08/16-F indoor split = a mere 442-cfm  |  7642/1.08/14-F indoor split = 505-cfm [I want 750-cfm; supply and returns at floor level!] Also, could be an unbalanced load on the evaporator circuits causing the TXV to shut down the refrigerant flow; among other things.
By using the various units' "base specification sheet data" from the dealer, you can determine if it is operating near its BTUH capacity rating. Some packaged units run a very high condenser discharge CFM airflow!
Some "Condenser Makes" will have different temp-splits. The 2-ton 10-SEER, GMC; Goodman; with the U-29 E-Coil delivers less btuh, or 23000-btuh, I subtracted a reasonable amount from the total of the wattage and come up with 19 to 20-F temp-split. That is "if" its CFM is 1400, --get the figures on the "different Makes." The figures are used to provide an idea of what the condenser temp-split should be for use by the unit's owner and the service tech.
With a properly sized system and proper evaporator airflow you will have consistent optimal nominal heat absorption removal capacity, coupled with requisite longer run-time cycles. I believe that optimal efficiencies by using a variable ratio latent/sensible heat loading, could be effectively achieved through the use of computerized system control components.

Air_Temperature_Drop_Through_Evaporator.jpg (49921 bytes)

Air Temperature Drop Through Evaporator Coil (1987 Period)
Indoor temperature and humidity load variations graph.
Refrigeration & Air-Conditioning (ARI) Second Edition,
Page 624, © 1987
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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.

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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.

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There are major Problems with most Manufacturer's Ratings Data

Air conditioners selected based on standard indoor conditions of 80°F Dry Bulb (DB) with 50% relative humidity (which is the standard ARI capacity rating condition) will be incorrectly sized for 76°F Dry Bulb. Unfortunately, many of  the major manufacters' provide information only at 80F.  

It would be a great improvement if the manufacturers' provided tables that presented the sensible and latent capacities at 76°F Dry Bulb for a variety of indoor humidities.
 

There is more to the "System Btu/hr Capacity Ratings in respect to the conditioned air space," than meets the eye. "It all depends on what is included or excluded in the capacity ratings in respect to motor heat Btu/hr that does nothing to reduce the total heatload of the conditioned space air." Motor heat is a factor to be dealt with, perhaps more so on the smaller units. I will list the formulas and illustrate the impact of the motor heat from the three motor sources.

Some possible Factors to consider when figuring the actual conditioned space Sensible Heat-Load to be removed and the variable Latent Heat-Load to be removed.

Some things you will find interesting concerning, "Gross" btu/hr ratings verses "NET" Btu/hr Ratings of A/C condensing units. I will do the illustration using my brother's system rated at 18400-Btu/hr
13-seer system.

We will say that "we need around 13,800-Btu/hr "NET" of sensible heat-load removal from the conditioned space."

CONDENSER TEMP-SPLITS - My Brother's Heil 12-SEER Condensing Unit
1.5-Ton - Rated at 18,400-Btu/hr, Condenser fan CFM 1400 (Total Condenser Watts 2222-watts X's a power Factor of 0.90 = 1999.8-watts X's * 3.413 =
6825-Btu/hr = MotorPower Btu/hr Additive + 18,400-Btu/hr "Rated Gross Heat Ejection" would be 25,225-Btu/hr / 1400= 18-F Temp Rise Cond./Split.

Additionally, adding the indoor fan motor Btu/hr heat: 5-amp at 115-volts is
575-watts X .90 = 517.5 X 3.413 = 1765.7-Btu/hr plus 6825-Btu/hr =
8590.7-Gross Btu/hr.

His condenser only gets a 10 to 12-F temp-split-rise. {1400-cfm X 12-split X
1.08} = 18,144-Btu/hr minus - 8590.7-Gross Btu/hr motor heat.
18,144-Btu/hr - minus 8,590.7 = a mere 9,553-Btu/hr NET heat absorbed and transferred from the conditioned space air! Add to that the .75 sensible .25 latent split! 9553 X's .75 = that would only be 7,165-Btu/hr Sensible removed from the conditioned space!

To remove 18,400-Btu/hr from the conditioned space, -the condenser would have to eject: 18,400-Btu/hr plus + 8,590.7 = + 26,991-Btu/hr
26991-Btu/hr / 1400-CFM condenser or around a 17-F Temp-split, NOT a 12-F split.

The new Goodman 13-SEER 1.5-Ton Condenser, 2-Ton Evaporator:
At 675-cfm 450-per/ton cooling | 85-F ODB | 63-IWB | 52% RH | 20-F ID Delta T | 18,600-Btuh
201-psig 100-F = 15-F cond. temp split - larger coil areas | 80-psig suction
Thermo Pride - Model OL-11 Oil Furnace Blower-Curve-Chart - Click Print , Click on Properties, Click on Graphics, Slide Setting to the Darkest Setting, click OK, or blower curve lines won't show up on the printed copy! (for Techs)
My scan of my doctored Thermopride OL 11
http://www.udarrell.com/Blower_Curve_Graph.tif

 SL11B.pdf  PDF File: Blower curve lines show in (blasted) yellow, use darkest printing page settings to get readable lines! Every manufacturer should furnish blower curve charts with their units and put them on the Internet for service tech's to download and print. Also, air conditioning codes should be updated in respect to proper sizing of the duct work which must include all the pressure inducing factors when sizing the supply and return ducts.
Any corrections or additions are welcome.

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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."
- Darrell U.

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DISCLAIMER:
I assume NO responsibility for the USE of any information I post on any of my Web pages, in E-Mails or News Groups.
All HVAC/R work should always be done by a licensed Contractor & properly licensed Techs! This information is only placed on these pages primarily for your understanding & communication with contractors & techs. This information is also for the edification of Contractors and Techs.
Never attempt anything that you are NOT competent to do in a SAFE manner! 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 Contractor

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