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Have a Question? Ask Dave

As long as Central City Air has had a website, we have had our "Ask Dave" page. It has always been a place where our customers and visitors could ask David Debien questions about their air conditioning and heating systems. Even though David has passed, we still offer our website visitors the same expertise and technical answers to all of their questions. We have a team of seasoned professionals on hand to answer any question you may have.



What do I do when my condenser is iced up and its 90 degrees outside?

Posted on 06.10.2019

Q:  My unit outside has ice on the lines. What is causing this to happen?



You notice that your system is running, but it isn’t blowing out cold air, so you go to take a look at your condenser outside and notice the line going from the condenser to the wall is covered in white “stuff”. What you are actually seeing is ice!

Ice forming on condenser lines

When the system is having trouble it can literally freeze up. The lines at the condenser and/or the evaporator coil itself get too cold then start to form a buildup of ice. This is often an issue with either the refrigerant charge or a restriction in the system.

The first step is to turn off your system so that the ice can melt as nothing can be done till then.

Iced Up Evaporator Coil

Check your house filters. If the filter is clogged, the restriction slows airflow over the evaporator coil causing it to freeze up, which will eventually causes the outside lines to freeze if it is left on for too long.
The second cause may be that the system is low on refrigerant.
It is also important to note that as the system de-frosts, there will be a large amount of water going down the drain, make sure the drain lines are free flowing and keep an eye on the pan to make sure it isn’t backing up.

After shutting off the system give us a call at 713-861-1977 to come out to perform a full system checkup.


I still have a system that uses the old R22 refrigerant. When did the change to R410A start and is R22 still available? Should I start looking into changing out my cooling equipment?

Posted on 05.23.2018

Q: I still have a system that uses the old R22 refrigerant.  When did the change to R410A start and is R22 still available?  Should I start looking into changing out my cooling equipment?


A: Refrigerant 410A was originally created in 1991.  The phase out of R22 refrigerant began as part of the “Clean Air Act” originally passed in 1973 and amended in 1990.  These amendments are what prompted the creation of R410A as an alternative to R22.  The phase out schedule was established in 1993.

2003 marked the start of the phase out schedule.  2010 was the year where R22 could no longer be produced or imported except for use in equipment manufactured before 2010.  January 1, 2010 also marks the date where any new equipment manufactured must use R410A refrigerant.  After this point, manufacturers no longer made R22 specific equipment.  2020 is when there will no longer be any production or import of R22.

The 2010 reduction was a 75% reduction of consumption and production and is about the point where the industry started to feel the impact of the phase out.  As of April 2017, suppliers of R22 refrigerant started to ration the refrigerant.  All HVAC contractors are limited on how much R22 can be purchased per month and the cost has already had a huge increase.

With less than 2 years left on the phase out schedule, we would recommend looking into changing your cooling equipment now.  Any unit that is still using R22 refrigerant will incur a high cost for repair should it leak refrigerant.


How do I know if I should have the air ducts in my home cleaned, repaired or replaced?

Posted on 03.28.2017

Q: How do I know if I should have the air ducts in my home cleaned, repaired or replaced?



This is a good question, which unfortunately doesn’t have an all encompassing answer.  There are many factors that contribute to the need to have your ducts cleaned or replaced.  Let’s discuss cleaning the ducts first.

According to the EPA “Duct cleaning has never been shown to actually prevent health problems. Neither do studies conclusively demonstrate that particle (e.g., dust) levels in homes increase because of dirty air ducts.”

The truth is, a light amount of household dust in your air ducts is common and is no more harmful than the dust you find regularly inside your home.  Duct cleaning is not something that must be performed as part of your regular maintenance and according to the EPA, you should only look into getting your ducts cleaned if:

•    There is visible mold growth inside hard pipe ducts.  
•    Ducts are infested with rodents or insects.
•    Ducts are fully clogged with excessive debris.

The above being said, there are reasons to look at replacing versus cleaning with the above items.

•    If mold is identified inside hard pipe, you should still have all of the external insulation removed and re-installed no matter if you choose to keep the existing ductwork and have it cleaned.  You can attempt to clean the hard pipe ductwork, but if the conditions that are causing the mold growth are not taken care of, the mold will re-appear.  There is also the fact that there are situations where you cannot clean 100% of the hard pipe ductwork.  If even one mold spore is left behind, you end up back at square one.

•    If your ducts are infested with vermin, you are likely looking at damaged ducts.  When a rodent chooses to make a nest from your ductwork, they have likely torn the ducts in order to do so.  If you have flexible ductwork, you will likely have to replace the damaged duct run.

•    If your ducts are fully clogged with excessive debris, there is likely a larger cause.  While ducts do accumulate debris over the years, it generally takes around 20-30 to accumulate an amount that would necessitate cleaning the ducts.  After that amount of time, the ducts likely wouldn’t be able to handle a cleaning and should be replaced.  If your ducts are newer and have accumulated enough debris to clog, there is likely a problem with air leaks in the ducts, which should be addressed.  You should also look into the filtration, or lack thereof.

  So, how do you know if your ducts are dirty?  

Properly designed ductwork is a closed air system.  The only air that enters your ductwork should be from the return air grille and the only way the air should be exiting the duct system is through the supply air grilles inside your home.

If you have proper filtration and are noticing debris coming out of your supply air grilles, you may have compromised ductwork.  It is best to have a licensed technician come out to check the integrity of the ductwork in the attic to see if there are any air leaks or loose ducts.

Sometimes with older ductwork, you could have a buildup of debris that sticks to the side of the ducts.  There is no way of knowing that this is occurring unless you have a technician remove one of the ducts at the plenum in the attic.  

The image below was taken during an evaporator coil installation at a customer’s home.  This older ductwork had compacted debris.  Due to the age of the ductwork and the fact that it was the lower R4 insulation value (Current codes require R8) this customer opted to replace the ducts.


If you suspect your ducts are dirty and aren’t sure whether you need to have the cleaned, repaired or replaced, feel free to give us a call to assess your situation and provide a plan of action.

Call Central City Air today at 713-861-1977

For the full article from EPA.gov:


How does leak dye work?

Posted on 10.06.2016

Q: How does a dye test work to locate a refrigerant leak in my system?


A: It’s fairly simple, actually.  When there is a large leak, you can easily see the buildup of refrigerant oil and an electronic leak detector can verify the location of the leak.  When there is a small leak, however it becomes difficult to locate as there is generally just a small amount of refrigerant residue.  In these situations, our technician injects the system with a dye, which runs through the system.   When the system has a small leak in it, the dyed refrigerant comes out leaving a residue that is normally transparent to the human eye.  With the dye, we can see this refrigerant to determine where the leak is located.

You can see the bright green areas in the image below.  This is the residue of the dye treated refrigerant that has leaked out.



What should I do if lightning strikes and burns out my electrical HVAC components

Posted on 09.23.2016

Q: What should I do if lightning strikes and burns out my electrical HVAC components?


When lightning strikes make sure that all equipment is turned off, check for fire and smoke.  Call the fire department, and the power company.  Once the power company restores power, you should call an electrician to make necessary repairs and to be sure that it is OK to turn the electricity back on. Next we recommend contacting a licensed HVAC contractor to check the air conditioning system (cooling and heating components) before you turn the system back on.

This picture was taken after a lightning strike

A technician will be able to check the wiring inside the equipment to make sure that there are no visible signs of damage, and diagnose the system for other issues that may have occurred. Hopefully the system can be repaired so you can get back up and running, it is important to be sure the system is safe to run. 


There are electronic components inside your condenser and furnace or air handler, it is important to have them all checked.  Sometimes the damage may mean that the unit needs to be replaced completely.   It’s better to be safe! 

Carbon Monoxide Dector

Posted on 04.06.2016

Question: I recently read an article where an entire office building was affected by a Carbon Monoxide leak.  I was wondering how likely it is to have CO leak in my home and what I could do to prevent it, or at least detect a leak if happens.


Answer: According to the CDC, “more than 400 Americans die from unintentional CO poisoning not linked to fires, more than 20,000 visit the emergency room, and more than 4,000 are hospitalized” (http://www.cdc.gov/co/faqs.htm). The best thing you can do is install a CO detector in your home.  At Central City Air, we use models that provided protection for all age groups and conditions, especially infants, children, the elderly and highly sensitive or ill people.  It is also very important to properly maintain your heating system, water heater and any other gas, oil or coal burning appliances.

We also try to educate our customers on maintaining a healthy home.  For more information on a healthy home, please visit this link:  http://www.centralcityair.com/healthyhome.html

If you are interested in having a CO monitor installed in your home, please give us a call today at 713-861-1977.

Dirty Sock

Posted on 04.04.2016

I bought my home in the Stone Oak area of San Antonio, brand new, on September 21, 2007. It has no heat pump but gas heat and air conditioning. Since the summer of '08, I have been experiencing a horrible odor, like living in a musty tent, coming from the air ducts as the a/c runs. Doesn't occur in winter with heat.

The A/C company that installed the system for the builder has been out several times, checked the ducts. They think that the system turning on and off, wet then drying, has something to do with causing the odor. The cleaned the coil, want me to run my a/c at 74 degrees to prevent it from turning on & off frequently, and most recently put an ozonator in the system. . The ozonator worked a litte, but a faint odor still exists, sometimes more than others, but better than before the device was put in the system.

The a/c company is ready to sell me a Guardian Air Cleaner System for better than $1200. Before spending this small fortune, I reseached Dirty Sock Syndrome on Google. Sounds like a coated coil is a better bet. Even though I don't have a heat pump, is DSS the problem? Either way, what should I do at this point?


From your account of things it seems that you may have what the industry nicknamed "dirty sock syndrome". When you go from the heat side to the cool side it is quite noticeable and every year it gets worse and lasts longer before the coils wash themselves off. We experimented with all the different ways to handle this problem and finally landed on a new coated coil. Reusing a contaminated coil to coat will not work, best to get a new coil and have it coated. Once this condition appears it seems to remain in the home and it reappears, coating the coil before installing has made a difference for us and works well. The coating we use is Bronz-Glow out of Florida.

As far as the advice you were given to run your air conditioner that cold, you will just be cold and may have some sweating windows but you will still have the dirty sock syndrome.

Is system in my new home sized right?

Posted on 06.29.2015

Question: Hello, we are having a new home built (3300sf) and the home is split into (2) zones. Zone 1 (bedrooms), 1727sf has a 1.5 ton installed and cannot keep up with Zone 2 (living) 1555sf, 2.5 ton. We have told them our concerns that the unit may be undersized. The A/C company has provided (4) calculations all with different final loads/numbers. The A/C company states” the calculations are correct”. I’ve hired a 3rd party A/C company and he has said the unit is undersized and duct work does not meet code. He has even following up in emails and I have given copies to the builder and the A/C company, but with no luck. The builder is trying to have us close in two weeks. My 3rd party A/C company says I should file a complaint with TDLR. We are at our wits end dealing with this issue. Do you have some info or suggestions for the next step I should take?

In our opinion:
New homes are built more efficient allowing less heat into the home.  A Manual J load calculation is used to help figure out the size of the air conditioner for the load.  Air conditioning equipment is engineered to remove dry heat; humidity is removed by condensation when the air moves across the evaporator coil.  Air (moves in and out of your home through opening and closing of doors, windows) infiltrates into the home naturally, the amount of grains of moisture in the air depends on the region you are in.

Mold or mildew is a great concern, getting the air conditioning right matters.  Here is what you may have with the home builder’s strict adherence to the Manual J without regard to total air flow:

An under size unit will run longer, not necessarily costing you more to operate, the longer run times means better humidity control. This is a plus.

On the other hand with an undersized unit, during peak load cooling conditions it will not have enough total cooling capacity for maximum cooling performance. With high ceilings or large open areas, a smaller system will not be capable of producing the airflow CFM needed to push air for proper circulation in the space. This is a big problem regarding your comfort in the space.

Today, most of the manufacturers systems are lower on total BTU (relates to tonnage) capacity, which may also prevent maximum cooling performance during peak load cooling demands. We suggest you find a mechanical engineer to run an independent load calculation to calculate the CFM needed from each supply duct to distribute the air across the rooms based on 98 or 100 degree cooling load conditions.

We also suggest you contact the TDLR for help.

We highly recommend that you look at inverter technology cooling systems as they have varying capacities that range from 40% of total cooling capacity for more aggressive humidity control and can rise to 115% of total capacity for maximum cooling performance. 

Does my a/c cause my lights to flicker?

Posted on 03.13.2015

Question:  My lights flicker, dim or don’t come on, is this a problem with my A/C and Heating system?

Answer:  A light flicker or dimming of lights happens when there is a dip in the voltage.  In many cases, this voltage sag is caused by any home appliances that require large amounts of power to start up.  The light flicker may only last a fraction of a second and usually isn’t anything to be concerned about, but if it happens all the time or is concerning, you should have an electrician out to make sure all wiring is secure and tight and that all equipment is properly grounded.  If your electrician gives you a pass then contact your utility company to check the wire and transformer servicing the house to ensure that there are no issues on the power company side.

When to replace an old electric heater

Posted on 03.13.2015

Question: My Electric heater is getting old, but it still works.  When do I need to consider replacing it?

Answer: As all equipment ages, it becomes less efficient and more prone to breakdown.  An Air Handler (electric heat), on average will last anywhere between 8-10 years depending on brand and manufactured date.  When the wiring inside the air handler unit becomes old and brittle, it can cause shorts and possible get hot causing an electric fire.  As your equipment gets older, we highly recommend having it serviced regularly and remember it is better to consider replacement than wait for a fire.

Is a furnace inside the house safe?

Posted on 03.13.2015

Question:  My furnace is inside my house, under the stairs, is this a safe place to install a furnace?

Answer:  The short answer is No.  Most City and State codes require a certain amount of clearance around a gas furnace for safety in which combustible materials are in safe range of the gas furnace itself and the gas flu is properly vented.  Look for other areas inside the house that would meet  the current International Mechanical Code.

Return Air size for a 1000 square foot home

Posted on 03.09.2015

Question: I have a 1000 sq ft apt with a 1 1/2 ton ac and 40K BTU heat unit. 4 rooms with 6 in. duct 2 rooms with 4 in. duct. What size return supply and grill should I use.

Answer: The minimum free air return is around 144 square inches per ton. Most common return grill size for 1.5 and 2 ton systems is 12 x 24 filter grille.  Supply grill size and style is usually determined by where the grill is installed in the ceiling. If the grill is closer to the outside wall, use a 3-way grill. If the grill box sets closer to an inside wall, use a 1-way grill.  Most common sizes are 10x6 or 10x8.

We don’t use 4” flex duct and recommend increasing to 6” for proper airflow.

To retrofit to an existing home’s application, take the existing grill down. Measure the grill box opening to determine correct grill size.  Note that all opening sizes are in round number. Example: 10 ¼ x 5 7/8 would be a 10 x 6 register.

Return Air size and type

Posted on 07.30.2014

Question: What is the proper size of return for a 3 ton 16 seer unit. Is having 2 return with 16x25 (16”) and 12x12 (9”) advisable? Also, we have 12 different size of vents in the house (3 rooms – master (2 vent), other room (1 vent each) , what should be the right size of duct supplies per each. I would appreciate if you could enlighten me. Thank you very much.   



One 16 x 25 return opening is good for approximately 2.5 tons. So, if you have the two 16 x 25 return grills, each on individual 16-inch flex ducts this alone is sufficient return air. The 12 x 12 helps. If the two 16 x 25 are twinned with only one 16 –inch flex duct, we recommend increasing  the 9-inch duct on the 12 x 12 to 12-inch to maximize total return air draw as it will only aid in circulation. Additional return air is not detrimental to the cooling system.


As far as the supply air registers:  The size and style of register depends on the size of the room, ceiling height, amount and type of glass and sun exposure to the outside wall. The key component is to have a grill that properly throws the air into a given room and to have a register that is not restrictive on the air delivery.   Depending on ceiling height ( 8-10 ceilings ) if the grill is located from the center of the room, we prefer a 3- directional grill. If the grill is located back further towards the inside wall we prefer a one way grill. This is designed to get as much coverage to the outside wall as possible.

Refrigerant Lines Freezing Up

Posted on 07.22.2014

Question: We've noticed out refrigerant line is freezing up at night. We just recently had it charged, which helped so that it no longer freezes up in the day time, but still does at night. The technician recorded the R410A service valve pressures at 340 psig and 99 psig during the day (90 degF ambient). He said the suction pressure was low, but sub cooling was good at 10 degF. He believes the low suction pressure is responsible for the freezing at night. The compressor trips off at night after icing up the suction line, presumably due to low pressure. After a couple minutes it turns back on and trips again in another few minutes, and continues to cycle this way. The tech is recommending that we upgrade our coil from a 4 to a 5 ton. Currently, all components are 4 ton. He says this will increase the pressure. Will this work, and is this the proper remedy? Please explain.

Answer: It sounds like the expansion valve is bad. The superheat has to be off and the oil temperature high, which is bad for the compressor. The coil doesn't need to be replaced especially with a 5 ton. The 4 ton matched system is better for humidity control. Replace the expansion valve and this should fix the problem.

Return Grille Sizing

Posted on 06.10.2014

Question:  How large does a return air grill need to be?  I have 1 right under my unit that is 7" x 32".  Is that enough?


Answer: The return size depends on the capacity of the cooling system, length of return run and size of the return chase. As a basic rule of thumb you can multiply the width by the height of the return grill and then divide by 144 to determine if your return GRILL opening is within range of the total system tonnage.   

Example: 12 x 24 return grill equals 288 square inches, divided by 144 equals 2 which represents about 2 tons.

Example: If you have a return chase or return duct over 12 feet long, then divide by 150 instead of 144. 7 x 32= 224 divided by 144 is approximately 1.5 tons cooling.

Return Sizing with Filtration

Posted on 05.08.2014

Q: I am installing a new unit and AC air return. What is the correct size of the return for a 4ton ac using a Dust Fighter™ 95. My chase to the attic coil is 24 x24 and 13’ long.(9’ vertical and  4’ horizontal to the coil in the attic)..........the return air is 24 x 30 and I want to use a  Dust Fighter™ 95 filter MERV 8 should I make the return air larger.  I cannot change the size of the chase thanks in advance for the help


A: It is our opinion that this a very restrictive filter to put in the wall that far away from the blower. The further away the filter is from the blower and the denser it is, the more it can affect the static pressure on the system. You also need to make sure that furnace can provide enough airflow to compensate for the filter restriction.  With this type of filter, you may need to double the return size and grill to compensate.


If possible, the best filtration application is one that is installed as close to the furnace return as possible.

Excessive Dust in Home

Posted on 10.15.2013

I have a problem with excessive dust use good filters replace regularly blower clean evap clean where is the dust coming from.


Infiltration is a source of dust. Also, the filter system is designed to reduce re-circulated material through the cooling system and ductwork. A filter’s job is to keep the equipment and ductwork clean. A lot of indoor/outdoor activity can allow dust into the home. Other causes of infiltration are: doors not properly sealed, attic access not properly sealed and canned lighting. If the material is fibrous and light in color it is most likely coming from carpets or cloth flooring (rugs). Also, the dryer being inside the house, linens and dry cleaning can also contribute. Ductwork infiltration is grainy and dark, unless you have white blown in insulation. Material coming from inside the house will be more fibrous and lighter in color. Sealing face plates and wall plugs can also help reduce infiltration.


Posted on 10.04.2013

What is going on with Complete Care?


To our customers who have recently received a letter from Complete Care (IAG), we would like you to know that we are (as always) committed to putting our customers first.

For more information on your warranty with Central City Air, please click here to download a letter from our President.

If you have any questions or comments, please e-mail us at: [email protected]

Supply Shortage

Posted on 06.26.2013

What is the status on repair parts?


We have been experiencing a shortage on repair parts and supplies across all vendors. We have been doing everything possible to get our customers the parts they need (including running our President and Vice President all over town). Because of this shortage we may experience longer wait times as many parts have to be shipped in from out of town. We apologize for the inconvenience.

Extreme Summer Heat

Posted on 06.18.2013

What is your scheduling looking like in this extreme heat?


Due to the extreme heat and high humidity (with temperatures that feel like a heavy and humid 104 degrees most of the time day and night), we have been responding to our customers who desperately would like to be cool again. As a result we will resume doing maintenance check-ups in July. Should your A/C stop cooling please call we will get you cool again.

Two Stage Coil?

Posted on 08.30.2011

Dear Sir,

I found your address on the internet from a radio broadcast in Dallas, Texas. The reason I am writing is I am curious about the two-stage coil. I have two Goodman units that were installed in 1994. I know my coils have never been cleaned and the HVAC has never been sealed. The units still work albeit less efficient. What do your two stage coils cost? I know you are in Houston and I am in the DFW area, but I am considering either upgrading some components or doing a complete refit. I have a single story home with approximately 3000sq. feet. I think it is 2950sq. feet to be exact. House faces North and gets plenty of West sun. I like your web site as it is one of the more informative out there.

Just curious. What would a bid for say two units Lennox that are 16 SEER and have a 13 EER to qualify for the Tax Rebate run? New Pads outside. New whips and electrical connections. 80-85% AFUE . Media filter (Honeywell so I can get replacement filters at Home Depot). Seal the system completely. Add some return air to match the units requirement. I was told I was short on return air.


The existing 1994 Goodman equipment and systems are at the end of designed life. Now is a good time to have a reliable air conditioning contractor look at your whole house and design systems to meet your needs within the home envelope. The quality of the installation is critical to obtaining maximum performance from any system. When you start the process it is a good idea to make your goal a top quality install job, with a smart designed system that uses well engineered equipment.

If your goal is to get the tax credit that is simple and very easy to obtain from anybody regardless of the integrity of the contractor. Think about the SEER shell game our Federal government is inviting you to play before you participate. Our founder David Debien always used to say do not design for SEER design for performance. Central City Air will not use any of the AHRI approved evaporator coil match ups except on the 1Q 23 Maytag equipment. We focus on humidity removal in Houston, Texas. Energy rated equipment match ups may not meet the humidity removal requirements we need. So be sure to do your due diligence.

The split coil you asked about is a Central City Air propriety coil, designed by our Founder David Debien. They were designed specifically to work with the 2 stage condensers for maximum humidity removal. We only sell them to our customers in Houston.

Regarding your request for pricing on Lennox 16 SEER that is matched to meet the AHRI 13 EER for the Federal tax credit: We are Lennox dealers, let me encourage you to get your pricing from a Lennox Premier Dealer in Dallas. You can go to the Lennox web site to look for Premier Lennox Dealers in your area. Lennox has a 17 SEER single stage and a 21 SEER 2 stage unit you may want to consider. Let me also encourage you to think about your goal.

TX Valve size

Posted on 06.23.2011

If we were to install a 3 ton condenser and a smaller 2.5 ton coil, what size should the TX valve be? 2.5 or 3 ton?


Central City Air uses adjustable expansion valves properly sized and installed correctly this allows us to fine tune the regulation of refrigerant flow so that the right amount of refrigerant goes to the coil. This occurs under all conditions and keeps the coil as cold as possible, resulting in maximum humidity removal and maximum cooling performance. We do not use fixed expansion valves that cannot be adjusted. The Valve type you would need would be a "B" valve.

Vacation A/C Settings

Posted on 06.11.2011

I'll be on vacation for a month in July. i live in Houston. what would be a safe setting for my ac unit. i'd like it as high as possible to save electricity, but don't want it too hot so i don't hurt my electronics or have mold problems.


If you are out of town for a while we recommend between 81-83 depending in the summer. This will still allow the system to run and pull some humidity out of the air.

Rusting Plenum

Posted on 12.03.2010

Hey Dave, I am fixing to buy a house that is 5 years old and while inspecting it I noticed on the AC unit for the upstairs that the top of the plenum had large spots were it was almost rusted thru. The owners realtor is having a AC company come out tomorrow. What suggestions do you have that might be causing this? This system also has some sort of fresh air ventilation system on it( any comments about this). This house is built by Ashton Woods. By the way I am one of your students from awhile back. Thanks Pete


The rust spot is most likely caused by a torn or missing spot of insulation inside the plenum. We suggest having this looked at to make sure that there is no moisture build up.

How to Eliminate Dust?

Posted on 12.02.2010



If you do not already have a Fresh Air Intake installed on your system, you should look into getting one. If you have one already or are looking to install a new one, you should make sure that you have one that has a damper that is timed with the system. Some Fresh Air Intakes are installed on their own timer, which will randomly open and close. You need one that is tied into the system so it opens and closes when the system turns on and off.

How hard is it?

Posted on 08.12.2010

I've got a two story house and only one unit, The downstairs and upstairs are always quite a bit difference in temperatures, what is the best solution to this problem? How hard is it to retro fit the house with two units?


Over the past 15 years, we have solved this issue with 1 system in a 2 story home. Currently, all of your ductwork may be on one supply plenum. Air (like water) flows down the path of least resistance. Heat also rises, which allows the upstairs to get warmer.

Our solution is to install two plenums. The first is for all of the downstairs ducts and the second is for all the upstairs ducts with a section of round duct pipe in between on the end cap. The air will flow through the main plenum into the second plenum for the upstairs ductwork, allowing additional cooling to the second floor. This will make the air as cold or colder than the first floor when pressurized assuming the duct design is correct.

For heating, the section of pipe between the two plenums has a motorized damper, which in the heating mode, closes a percentage. This prevents over heating of the 2nd floor and better heating to the first floor.

Air Filter

Posted on 08.12.2010

What is the best type of air filter to use in the return air ? I've used the Filtrete 1000 (red) filter but it seems like it gets dirty fast, which I'm assuming makes the a/c work harder. I change them once a month, but they look pretty dirty after two or three weeks.


When space permits, we recommend an inline 5" pleated media filtration system within 1 foot of the furnace in the attic for greater filtration. If a filter gets dirty quickly, we recommend looking at sources of infiltration, such as leaking light fixtures, doors and windows. Also, carpeting and indoor clothes driers compound the issue.

Uncontrolled fresh air enters your house through cracks and crevices in your home, through the air conditioning system, and through leaks in the duct system. Uncontrolled fresh air can be very undesirable.

Also, the further the filter is away from the blower and the more dense the filter, the greater the restriction on system performance. The filter is picking up material like it should. Why is it getting so dirty in 3 weeks is the bigger question.

Higher humidity in house

Posted on 07.25.2010

House is two stories around 2400 sq feet with one Lennox 4 ton unit with a 5 ton ADP coil, two thermostats with zoned ducts. No issues cooling the house even on the hottest days.

The problems I am having are short run times and elevated humidty...around 56% on average.

I know that having one system with a two story house is not ideal and is the low cost option for most builders. Is there anything that can be done to lower the humidity


Humidity in the home, on average should be around 55% or lower. The 5-ton coil on a 4-ton condenser is too large. Humidity control is only a by-product of heat removal out of the air during the conditioning process. An oversized evaporator coil will not get cold enough to absorb moisture out of the air. The coil size determines the major balance between dry and wet heat removal. The coils remove dry heat (temperature) and the wet heat (humidity). The coil size determines this ratio. The larger the coil is size, the lower the humidity removal. In many cases, a smaller coil can increase the humidity removal by 30% to 40% resulting in greater dehumidification. After extensive research, we have found that having a matched or oversized evaporator coil will not control humidity enough. Rather it increases the humidity level in the home, especially at night. The reason is that the evaporator cannot get cold enough to properly dehumidify the air, causing your air to feel sticky and humid.

We recommend a 4-ton condenser with a 3-4 ton evaporator coil in the horizontal application. We also recommend an evaporator coil with an adjustable thermal expansion valve to help adjust refrigerant charge for maximum performance.

You also need to make sure that the home's envelope is correct. Make sure that the attic access, canned lighting , windows and doors are properly sealed and weather stripped. You may also need to get the home closer to neutral pressure to reduce moisture and dust infiltration, which can be achieved with a Fresh Air Intake

Blower Motor Runs Continuously

Posted on 05.26.2010

I have a York HVAC system, and the inside blower motor is running continously. In addition, yesterday, I noticed smarks coming from the capacitor outside of the blower housing. I turned the unit off, and there was also water dripping on the outside of the unit.

The HVAC unit runs fine today, but I didn't want to take my chances so I turned the unit off from the breaker box.


1. What is causing the water to be dripping down onto the blower housing?
2. What could cause the sparking (burned wires) on the capacitor?
3. What could be causing the blower motor to be continously running even when I turn the thermostat to "off"?


It sounds like the system has an iced up coil and the water is shorting out the blower capacitor. The blower relay may also be damaged due to the dripping water. You need to call in for service and check the filters as well as the refrigerant charge in the system. They also should check for a dirty coil and blower wheel.

A/C Condensing Coil Freezing Up

Posted on 05.08.2010

The problem we have is our a/c condensing coil freezes up, causing the house to not cool properly. It seems to be happen during the late afternoon/evening, when the temperatures get warmer and it gets more humid outside, which causes the system has to run more.

In March 2005 we had a new Trane a/c and heating system installed in our 2396 square ft. - two story home. We also had radiant barrier paint installed in the upper and lower attic's, and additional bat insulation installed in the attic floor. The house was a combination of brick and vinyl siding; however, during the summer of 2008 we had the vinyl removed and had hardi plank siding installed, along with new insultaion. We also had our standard windows removed and had new insulated windows installed. The a/c condensing coil has frozen up each summer since installation, and when this happens water drains out of the overflow line on the side of my house, but the company who installed the system was unable to determine the cause.

On May 6, at approximately 10:00 p.m., the temperature upstairs was 82 degrees, even though the thermostat was set for 72 degrees.

On May 7, I called the company that installed the system and they sent out a technician who discovered the condensing coil in the attic was leaking freon. The Tech then checked the freon at the outdoor unit and discovered that the freon was low by about 6 - 8 pounds. The Tech stated that this could be the cause the condensing coil to freez up, but last June the same condensing coil froze up and they checked the condensing coil and it was fine.

The Trane components are a 4-ton variable speed blower - two stage gas furnace w/ comfort R, a 4-ton XL16i - two stage condensing unit, a 4-ton TXH high efficiency coil, along with an Aprilaire electronic air cleaner, all were installed in March 2005.

Since the company has been unable to determine what is causing the a/c to freeze up, we are now wondering if the system that was installed is sufficient for the size of our home.

Your thoughts on our situation would be greatly appreciated. Thanks!


I do not believe capacity is the problem for the system freezing up. A freeze up is generally due to loss of refrigerant or lack of airflow. You may not have a leak in the coil, maybe a leak in the refrigerant lines in the wall. When the siding was replaced they may have kicked the copper. A good leak tester should be able to locate a refrigerant leak.

You may also have issues with the comfort and not having the airflow settings correct. Have the contractor leak test the system and Freon lines to check for any leaks. Also have them check his airflow settings.

Dirty sock syndrome

Posted on 12.22.2009

Do you have an update to this stinky issue. I seen this info on this link and was wondering if you had any updates to help with this.


There have not been any advancements in combating the “Dirty Sock Syndrome”. We continue to use the Bronz-Glow coating to great effect whenever we have a customer who has this issue. It is still the best thing out there.

Veritcal or Horizontal Unit

Posted on 12.11.2009

We are looking at doing a fairly large additiona to our small 1930's home and we are having a very hard time trying to figure out how to fit the a/c units and duct work in. we are thinking about maybe doing a verital unit? are vertial units better or worse than the horizontal units? do you have a preferance?


When space permits, the horizontal application is the best approach. A horizontal slab coil with an adjustable thermal expansion valve allows for a colder coil, which will dehumidify and cool the home much better. Also, the horizontal coil application will have an emergency pan directly under the coil to catch overflow. They can be cleaned and serviced much easier than upflow coils.

Upflow coils are very difficult to access for cleaning. The design does not allow for the aggressive cooling and humidity control required along the gulf coast. The basic design has the evaporator coil placed on top of the furnace, so any overflow falls down onto the furnace. However, a good upflow installation is better than a tight limited service application with horizontal equipment. Installation and quality work matter in performance!!