with Darrell Udelhoven - HVAC Contractor & Technician since the Mid-1970's Retired

First, don't mistrust every H-VAC contractor, most of them are okay & trustworthy.

The reason air conditioning consumers are easy prey for a rip-off scam artist, is that they are not knowledgeable enough concerning H-VAC systems.

Therefore, air conditioning consumer's have a tendency to always believe what they are told by the A/C technicians.

When you acquire sufficient knowledge, you will know how to qualify the contractor's on the telephone before you allow them to make a service call or bid on equipment replacement.

I will provide you with adequate basic H-VAC knowledge so you will be enabled & empowered to protect against the worst rip-off scams.
HVAC Efficiency Overview My Audio overview; listen while you do other things/last part on Oil & A/C airflow

There are simple ways you can check your A/C system with a thermometer.
Using a low cost wet bulb instrument, & low cost anemometer you can actually ballpark the BTUH operating performance of your A/C or heat pump.

Undercover AC repair in Arizona Search Videos showing Rip-Off scams

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 & more.

I don't know any local Techs that do it or know how to do it.

Here is a Consumer Affairs Comment Form: Consumer Comment Form

Always begin with a thorough Home Energy AUDIT that shows all the options for lowering the heat-gain & heat-loss, then after reducing air infiltration, etc., have a room by room manual J heatload calc performed. A reduction in equipment sizing will usually greatly improve the duct system performance.

This is where the greatest savings in both heating & cooling will accrue; this will help in the down-sizing of equipment.      

"The 'proper heatload' on the evaporator coil must be established"
Check and thoroughly seal all the ductwork! For efficient operation, always check the return air temperature at the blower & at the Return Air Grille(s) to know whether it is drawing hot air from the attic or garage areas.

What I stated above, that ought to be done is far more important than SEER rating; as that will determine the SEER achieved & the energy savings.

Then do a manual J room by room heat-gain calc with the option shown so you can do everything possible to reduce all sources of heat-gain & heat-loss, greatly reducing both heat & cooling BTUH equipment sizing.

Before you do anything else, educate yourself enough to "ensure that you request the proper things be done in the proper order of sequence." Checking ductwork & Airflow Checking Static Pressures  is Critically Important. As is knowing the operating feet per minute (FPM) velocity, the CFM & BTUH to each room along with the Total CFM airflow & BTUH.

Find the best way to save energy in your home, use your zip code. Profitabiity of Energy efficiency Upgrades | Hidden cost of Home energy Use

Then have a manual "J" heat-gain / heat-loss load calc done, followed by a manual "S" for equipment sizing & then a manual "D" for proper ductwork sizing.  All registers, grilles, filter racks, & diffusers must be located & sized for optimal efficient performance of the system. Order Turning Vanes for long radius 90-ells; use long radius 45's.

The correct sizing of residential air conditioning systems & ductwork is crucial to ensuring proper indoor space conditioning, equipment performance, and economical operation. Unfortunately, many A/C contractors measure “correct equipment sizing” by the system's ability to meet any indoor thermostat setting at any outdoor temperature. That method of sizing will lead to inefficient operation for the vast majority of conditioning time. Air conditioning systems “must be sized to meet typical or average indoor and outdoor conditions to ensure proper air mixing, filtration and dehumidification of indoor air across seasonal variations.”
A Major Oil Furnace Airflow Problem Fix
Regal & Hallmark & nearly all Oil Furnaces - Installation manuals
Download the installation & service manuals from ABOVE LINK BELOW LINK MAY NOT WORK! 
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.
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. 

Every manufacturer should furnish blower line curve charts with their units and put them on the Internet for service tech's to download and print. A blower curve graph chart, for discerning the variables of ol furnace belt drive blowers. 

Observe how easy it is to fall below the required CFM with a quarter horse blower belt drive motor that was standard with 112,000 btuh output oil furnaces. Measuring the static pressure of the duct system & using an anemometer to check atual airflow is a must! The Thermo Pride OL 11 Oil furnace requires 1164-CFM of airflow to keep temp rise within 90-F.

That would require at least a 2.5-ton A-coil at 1125-CFM to get close to enough airflow, a 2-Ton coil is only 900-CFM.


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

Any good Tech should already know what I am going to illustrate here; this is for Homeowners & any who can use the least costly way to deal with this too common a problem in the cold North Country. 

We are moving into the cooling season; however, any changes in equipment should consider how every component matches with optimal airflow efficiencies.

My lowest cost solution to the cold climate oversized Oil furnace with a small tonnage A/C evaporator coil which requires nearly half the airflow as heating:

I ran a check on my late brother’s home & the summer cooling heatload is about 14,000-BTUH. 

The original scenario, had much less airflow than required for 1.5T cooling; its 2-T A-Coil wouldn’t flow 1150-cfm for heating

I did a lot of other figuring; 45,000-BTUH output should heat that small single story home. 

However, with the 140,000-BTUH input, 112,000 output Oil furnace installed; the nozzle size can be dropped from one gal an hour (we’ll use 139,000-BTUH input) to .75 @100-psi, the BTUH drops to 103,500 input, this furnace tested at .74% efficiency; *103,000 = 76,590-BTUH.

Using a 90F heating temperature rise, which Thermo Pride can stand; (90*1.06 here) 76,590 / 95.4F is 803-cfm.

Therefore, the 2-Ton A-Coil will handle the CFM; mounted +6 inches above the furnace, it has the flow capacity to work okay in both heating & cooling modes.

By installing a direct-drive multiple speed blower motor, you could simply adjust the RPM to the A/C & furnace CFM requirements.

Therefore, solution is to install a multiple speed direct drive motor with the fan relay energizing the cooling speed tap. 

This rather common situation in cold climates seems not to be properly addressed my Techs, & the HO does not know why cooling & heating don't work well.

We should all work to improve efficient use of high cost energy ... so America & everyone wins. 
Home & small business owners, here is a very low cost way to check an A/C or heat pump's cooling BTUH performance. Get a low cost Testo 605 Tester to get the Supply Air Wet Bulb temp & Return Air Wet Bulb temp so you can ballpark figure actual BTUH & EER performance; they would charge big-money & virtually none know how to do it: 
Testo 605-H2 Fast Accurate Wet Bulb 
Home & small business owners & everyone, very low cost anemometer to get airflow FPM Velocities at Supply Registers or Return Air Grilles, which you can convert to CFM:

Also, get a low-cost digital flat-headed pocket Thermometer to use flat on the piping; these test instruments will PAY big returns!
Take the Supply Air & Return Air wet bulb temperatures & interpose them on the enthalpy chart linked below.
CFM X* 4.5 @sea-level, or use X* 4.35 if 1000' above sea-level, X* change in enthalpy = BTUH (Ballpark) Operating Performance.
"U Must Right Click Link & open in New Tab," look-up wet bulb enthalpy figures on enthalpy chart," & figure enthalpy change times the result of the CFM X* the factor.
Wet Bulb Enthalpy Chart  Print chart 

Video    Best

:  Installing  &

Cooling Coil Best Practices NOT shown in this .

  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 RIGHT
Rules of Thumb for Duct Systems  - Hart&Cooley

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 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 Home Inspector's look into the boot areas for clues of problems...

Rules of Thumb for Duct Systems  - Hart&Cooley

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.
Have or do a manual J heat-gain calc for each room. If a room calls for 3,000-BTUH; first divide 12,000-BTUH by the CFM PER TON you want to use.

I.E., Wet coil, 12,000/400=30-BTUH per each CFM; Wet coil 12,000/425=28.235294; 3000/28.235-= 106.25-CFM;  Dry coil, 12,000/450= 26.6666-BTUH; 3500 / 26.6666= 131.25-CFM
If register/diffuser has the same (Ak) free-airflow-area, as the duct run!

Room calls for 3,500-BTUH, using 450-cfm per/ton dry coil or 26.6666-BTUH per CFM= 131.25-CFM. 
I.E., 6" rd duct .6*6=36*.7854=28.2744sq.ins/144=0.19635-sq.ft.; 131.25-cfm / 0.19635-sq.ft= or 668.4-fpm velocity.

  •  SP2 = (rpm2/rpm 1)2 X SP1 = SP2

Required fan motor horsepower (hp) varies as to the cube of the rpm speed:

  • hp2 = (rpm2/rpm1)3 x hp1 = hp2

CFM Fan delivery varies directly as to the fan RPM speed:

  •    cfm2 = (rpm2/rpm1) X cfm1 = cfm2

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

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The Testo 416 Airflow Test Checking airflow - should always be performed before charging a system!
Description of 416 Testo Telescoping Vane Anemometer - A MUST
The Testo 416 Airflow Test Checking airflow 

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

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

Getting it right makes all the difference in the world. 
This Energy Star ACCA pdf is interesting & confirms what many of us have been preaching, including educating the potential customers!

Scroll down to page 5 Market Conditions, & study to learn how we can all profit, customers included...

There are more ACCA links but this is a good starter document. 10/05/10

Residential Quality Installation Check List
 Use to pre-qualify Contractors

Darrell Udelhoven - HVAC RETIRED - udarrell

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Darrell Udelhoven - (U-dl-hoven)

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Darrell Udelhoven - Bloomington - Lancaster - Grant County - Wisconsin