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How to Clean AC Evaporator Coils

Photo tutorial showing how to clean AC evaporator coils with no-rinse spray foam cleaner.

If you’re not comfortable cleaning the AC evaporator coils yourself, at least you’ll what’s needed when calling a Heating, Ventilation and Air Conditioning (HVAC) professional.

Central Air Conditioner Routine Maintenance

Routine inspection and maintenance is very important to catch problems early and save on your electric bill. I recommend hiring an HVAC technician to inspect and maintain the AC system twice a year; Spring and Fall are best before the summer or winter season begins and you really need your system.

The most important thing a home owner should do is regularly change the air filter every month. I installed Honeywell touchscreen 7-day programmable digital thermostats that reminds me when it’s time to change the air filter. A dirty air filter will increase your electric bill as the system struggles to heat or cool your home.

Other things a careful and knowledgeable homeowner can do is clean the evaporator coils.

AC Air Handler Components

The following photo is the central air handler in my attic. It is known as an “upflow” type because air enters from the bottom and exits out the top. The unit combines a natural gas furnace and an air conditioning evaporator coil. It has three major sections:

  1. Blower motor – bottom
  2. Gas furnace – center
  3. A/C evaporator coil – top

The entire air handler sits on a secondary drain pan with a cutoff float switch. The purpose of the secondary drain pan is catch water in case the condensate drain line becomes clogged or the main condensate pan rusts through. The secondary pan will catch the water and eventually activate the float switch to shut down the entire unit before it overflows and ruins the ceiling. Too often, the secondary drain pan becomes rusty and fails to hold the water.

AC Evaporator Coil Cleaning: Air Handler Components

AC Evaporator Coil Cleaning: Air Handler Components

The blower motor forces air upward (recall my air handler is an “updraft” or “upflow” type) through the furnace and air conditioner evaporator coils. The Heat and Cool functions of the thermostat ensure that either the furnace or the air conditioner operate, but never both at the same time. The supply air plenum box sits on evaporator coil sheet metal cabinet. Two large flexible ducts are connected the plenum box. The large trunk flex ducts connect to rigid duct board distribution trunk ducts that lay on the attic joists. Several smaller flexible duct branch lines are taken off the rigid trunk duct to supply air to vents throughout the house.

HVAC Air Handler Evaporator Coil Cabinet, Plenum and Flexible Ducts

HVAC Air Handler Evaporator Coil Cabinet, Plenum and Flexible Ducts

How to Clean AC Evaporator Coils

Before you begin, turn off the air conditioner at the thermostat.

The evaporator coil access panel must be removed to access the coils. This is a closeup of the evaporator coil access panel, which is fastened with nine 1/4 inch sheet metal screws and sealed along the bottom with metal foil HVAC tape.

Evaporator Coil Cleaning: Evaporator Coil Case and Access Panel

Evaporator Coil Cleaning: Evaporator Coil Case and Access Panel

Remove the access panel screws with a socket wrench and peel away the metal foil tape along the panel edges (if any).

Remove the Evaporator Coil Access Panel

Remove the Evaporator Coil Access Panel

The access panel is removed exposing the AC evaporator coils in the following photo. The evaporator coils are basically a heat exchanger, cooling the air inside the house and transferring the heat to the outside condenser unit.

AC Evaporator Coil Cleaning: Access Panel

AC Evaporator Coil Cleaning: Access Panel

A-Frame AC Evaporator Coil

My AC unit has what’s known as an A-frame style evaporator coil. The coil has a two halves joined together like the letter A and sits on a condensate drip pan. The drip pan forms a moat under the coils to catch the water dripping down as warm humid air from the house is chilled as it moves across the cold coils. The bottom of the A-frame is open so the air can flow through.

A-Frame Evaporator Coil

A-Frame Evaporator Coil

The better evaporator coils have a plastic condensate pan to that won’t rust through. If the condensate pan were to develop a leak – or the condensate drain were to get clogged up, the water will do one of two things:

  1. Overflow and pool in the safety condensate pan under the whole unit, which will eventually fill up and trip the safety float switch, shutting down the unit. The purpose of the float switch is to prevent the pan from overflowing and causing water damage to the ceiling and rooms below.
  2. If the unit doesn’t have a safety pan under the unit, you’ll have water damage right away.

On a typical summer day, the evaporator coils can generate gallons of condensate water as it dries and cools the air inside the home.

This article is continued in How to Clean AC Evaporator Coils – Part 2.

Take care,
Bob Jackson

Copyright © 2014 HandymanHowTo.com   Reproduction strictly prohibited.

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82 Responses to How to Clean AC Evaporator Coils

  1. Faith July 14, 2009 at 8:30 pm #

    Thanks for providing this information to your readers. This would really give them a helping hand to learn more and would give them idea on how to clean their own air conditioners at home.

  2. Ray Winter August 21, 2009 at 11:03 pm #

    Hello,

    Thanks for this information. Gave me the confidence to inspect mine and clean them. They were absolutely filthy! I never imagined they would be after just 8 years.

    THANKS!!!

    Ray Winter

  3. gary January 4, 2010 at 6:42 pm #

    if i use the frost king cleaner in the winter, will i need to rinse?

    • Bob Jackson January 4, 2010 at 7:54 pm #

      I think your concerned about the A/C being shut off in the winter and therefore no water condensation to further rinse the coils as there would be in the summer when the system is running. The instructions say it’s a “no rinse” product and I didn’t see disclaimers about seasonal/winter use. The foam breaks down nicely and drains away. You might shut off the heat for an hour so the fluid can do its work.

      A second application at the start of summer wouldn’t hurt if in doubt.

  4. Cindy June 8, 2010 at 4:38 pm #

    Many thanks….as a single mom, I winced at having a tech come out and charge me for something that I could do if I knew how.

    • Bob Jackson June 9, 2010 at 7:09 am #

      I’m pleased the article helped you. Often times the work is not difficult, the problem is finding the specialized knowledge to do the work.

  5. George June 18, 2010 at 10:55 pm #

    Ok I am having issues.. I have had numerous problems with my 3 ton intertherm heatpump. Just about 4 years ago I had a defrost board replaced. Then a fan motor outside the unit.. 3 years ago I had a compassador replaced. Last year I had a tech check out my attic unit and he told me my coils and everything were amazinely clean.. Two month later I need a fan wheel changed, looks like a rat wheel. Ok 2010.. I noticed a dimming of my lights and a few days later a tech came out and told me my compressor was gone, and also whomever hooked up my compassador had the wires backwards and thus my compressor went bad..

    Ok the tech replaces the compressor, then the tech tells me I have another huge problem, that my reversal valve is bad and also maybe my defrost board.. So I was a freaking week in 90′ weather and a different tech comes out and is walking round and round and is on his phone, comes to me 10 minutes later and tells me my unit is fixed and all it needs was a screw for the defrost board and a little piece of plastic behind it.. He left but my air wasn’t blowing as hard or cold, a little cool, it took almost 3 hrs to cool home down from 110′ to only 78 while on 68′ thermostat.. Now here is another problem, I come home and unit is on 71′ thermo settings it’s says 79′ on reading and it’s not so cool. So, I call the tech and he tells me I need a good coil cleaning, never looked up stairs in the attic and just because my outside unit is a little dirty but I keep it clean.. I then go outside to rinse down unit and I see my compressor copper pipe to another unit that looks like a huge soda can dripping, then that copper pipe to the pipe outside the unit into the wall with insulation wrap and all pipes are frozen.. I tell my son to turn off the unit and the frozen ice disapears instantly. I tell him to turn it on again and the rightside of all copper pipes because to freeze and the whole pipe turns frosty..

    what do you think is the issue, the idiot tech tells me I am mistaking and if I get all of my coils clean I will have better cold air.. It’s ludircrous.. Maybe I do need a cleaning, but one tech tells me my defrost board needs replaced because his reading weren’t correct and the connection wasn’t right or the reserval valve is shot..

    Why would my outside pipes frost up and no real cold air inside my unit..

    Lastly, I have a contract for the great AHS. American Home Shield and the fly by night idiots are amazing.. One company tells me the other screwed something up and this is why you have so many problems and then one tech from the recent company tells me after he replaces my new compressor I have other issues and a new tech from the same company screws the defrost board together and does his reading and leaves, what is a customer to do.. thanks for any help..

    • Bob Jackson June 19, 2010 at 9:00 am #

      There’s so many issues going on that you should have an full installation audit of your Intertherm heat pump. Contact an authorized Intertherm distributor to explain your problems and order an audit.

      If you’ve been working with the local Intertherm dealers and believe that’s part of the problem, contact the manufacturer – NORDYNE – at:

      NORDYNE
      Customer Service
      8000 Phoenix Parkway
      O’Fallon, MO 63368
      Phone: (636) 561-7300
      e-mail: mfg_sales@nordyne.com

      > Lastly, I have a contract for the great AHS. American Home Shield and the fly by
      > night idiots are amazing..

      AHS should be sending only Intertherm authorized HVAC technicians to service your system. AHS has had their share of complaints and lawsuits.

      > Why would my outside pipes frost up and no real cold air inside my unit.

      The outside pipes are frosting because refrigerant gas is (too cold) inside the pipe on its way to the compressor. The pipes will be cool, but something sounds wrong if the pipes are freezing, like the evaporator coil inside the house isn’t working right. The evaporator coil is a heat exchanger that flashes the warm liquid refrigerant to a cold gas through an expansion valve. The cold gas circulates through the evaporator coils as the fan blows warm inside air over the coils. The indoor air gets cold and the refrigerant gas warms up. If the gas is below 32F as it returns to the outside compressor, then the cooling process isn’t working as it should and you’re too warm. The problem could be a number of things: bad expansion valve, wrong gas pressures, compressor problem, etc. The exposed pipes should be insulated, too.

      Post back and let me know how your situation is resolved.

  6. Dan July 10, 2010 at 10:37 am #

    Thanks for a well written DIY article and good pictures to help illustrate what is involved.

  7. Alan August 27, 2010 at 12:10 pm #

    Thanks for the great article. After I gained access to clean my coil, I saw that my A-Frame coil does not have a top, so to speak. I’m referring to the flat piece of metal which sits on top of both coils, at least in the pictures I’ve seen. Witout this piece, there is about a 2 inch gap between the coils. This would seem to be an issue to me, as the air-flow can move thru this gap without being filtered thru the coils. Is this an issue I should adress? Thanks.

    • Bob Jackson August 28, 2010 at 8:04 am #

      You are correct – a missing A-frame cap will allow air to bypass the coils lowering efficiency. Contact an HVAC company and maybe they can fit a new cap. Makes me wonder what happened to the original cap? Did it come loose and get blown into the plenum or ductwork and is stuck up there blocking the air flow? You should have a look with a flashlight and small mirror.

  8. Alan August 28, 2010 at 7:55 pm #

    Thanks for the advice Bob, I’ll definitely check into it further.

  9. Brigitte March 21, 2011 at 2:21 pm #

    Hi Bob,
    How do I remove the evaporation coil for cleaning? If this is too difficult or risky. Is there a good way to clean it efficiently without removing it?
    Brigitte

    • Bob Jackson March 21, 2011 at 7:27 pm #

      The evaporator coils cannot be removed for cleaning because the refrigerant lines are permanently connected and would have to be cut.

  10. hoppinjohns April 23, 2011 at 4:41 pm #

    Your post got me started to clean my HVAC coil. Your pictures are great and particularly helpful.

    Mine is a horizontal installation because of its greater size. It’s more difficult to work with but exactly the same steps as yours.

    I went one step further to take the side metal sheet off so that I can wash, spray, and vacuum from the inside side of the evaporator coils under the coil dome. My coil inside is filled with insulation feathers, the type of insulation the builder pumped into attic. A few years ago, the intake air return was loose and fell off half way. The AC sucked in a bunch of insulation. They were trapped on the coil but on the inside side. They probably blocked a significant amount of air flow, not to mention the bad air they produced. It took me a long time to vacuum them off. I made a special vacuum head to use on the delicate coil.

    Thanks for your posting.

    • Bob Jackson April 23, 2011 at 6:06 pm #

      Wow! I can just see all that blown attic insulation plastered on the face (upwind side) of the evaporator coils. You were fortunate to discover the problem and clean it off. I’ll bet your electric bill this August is 30% to 40% less than last year!

      Thanks for sharing your experiences.

  11. Theresa Bell May 17, 2011 at 1:23 pm #

    My daughter is having a home inspection problems. The owners or agents are not completing the work to the satisfaction of the inspection, who has made 2 trips. The problem, according to her home inspector is the coils are shot. I recommended that she take the advice of the person she is paying, her home inspector, ask for her earnest money back and start looking for another home.

    • Bob Jackson May 17, 2011 at 4:40 pm #

      It’s a buyer’s market, look for another home.

  12. chris lenahan June 12, 2011 at 11:15 pm #

    I have a mobile home 14×66. I i have an intertherm 13-seer. Where are is the a-coil locacated. is this the same as the evaperator coil? is it located in the outside unit or somewhere underneath my home or inside the house. I perplexed. i cleaned the outside coils in and out changed the thermostat and still not working properly. please help. thank you

    • Bob Jackson June 13, 2011 at 6:42 am #

      > Where are is the a-coil locacated. is this the same as the evaperator coil?
      The evaporator coil is inside the air handler and may be a flat style coil (like a car radiator) or an A-frame style.

      > is it located in the outside unit or somewhere underneath my home or inside the house.
      The air handler could be underneath the mobile home or inside a closet. It would help if you provided the model # of your Intertherm A/C unit.

      > i cleaned the outside coils in and out changed the thermostat and still not working properly.
      Have you changed the A/C filter? Look around the house for a main air intake duct, it may be next to the air handler. A clogged A/C filter will restrict the air flow, interfere with cooling and run up your electric bill because the unit will be running longer than necessary.

      You may want to call an air conditioner service company to inspect your unit and perform a seasonal tuneup – check the refrigerant charge, inspect the coils and electronics, change the air filter, etc. They can show you where the air handler and air filter are located. Cost is typically in the $70 to $80 range.

  13. joel July 6, 2011 at 10:32 pm #

    my unit looks like the above pict. but the header section isn’t insulated above the evaporator. the ducts are insulated upto the distribution header box but not the header itself; shouldn’t the distribution header box be insulated also/ what type insulation? Attic very hot here in South Texas..Takes awhile for just main cold water line to cool down from one end of house to other end!!

    • Bob Jackson July 7, 2011 at 4:53 pm #

      The sheet metal header box above the evaporator coils should be insulated. Do you evidence the interior insulation duct board is missing? You could cut and fit sections of fiberglass duct board inside the box.

      1. Turn off the system and lay a towel or piece of cardboard over the coils to protect them from overspray.
      2. Measure the sides of the header box and cut sections of duct board to fit. “Dry” fit the boards to get everything perfect. The foil side will be showing.
      3. Spray the fiberglass side of the ductboard with a generous coat of 3M™ Super 77™ Multipurpose Adhesive.
      4. Spray the interior sides of the header box with the 3M Super 77 spray.
      5. Wait several minutes for the 3M Super 77 adhesive to bubble up and become tacky. Instructions are on the can. This will create a permanent bond.
      6. Press each section of fiberglass duct board to the side of the header box, foil side showing. Take care to align it perfectly as you won’t get a second chance.
      7. If you happen to cover up a duct hole, you can cut out the opening with utility knife after setting the duct board. Start in the center of the duct hole and work your way to the perimeter of the circle.
      8. Remove the towel or cardboard protecting the coils before closing up the header.

      Foil faced fiberglass duct board can be purchased from a HVAC or Building Supply company.

  14. Morgan July 11, 2011 at 12:34 pm #

    to clean the coils, all i do is spray them with a cleaner or wipe down as well after spraying?

    • Bob Jackson July 11, 2011 at 4:46 pm #

      Spray the coils with the foaming cleaner. Do not wipe or touch the coils because the fins are delicate and will bend blocking the air flow.

      • Derek January 4, 2014 at 12:17 pm #

        Is Web coil cleaner a good product.

        • BobJackson January 4, 2014 at 1:41 pm #

          Hi,
          Web coil cleaner is intended for the outdoor compressor coils. Because the aerosol can contains propane and butane the Material Safety Data Sheet (MSDS) states:

          “FIRE/EXPLOSION HAZARDS: MATERIAL IS HIGHLY VOLATILE AND READILY GIVES OFF VAPORS WHICH MAY TRAVEL ALONG THE GROUND AND IGNITED BY PILOT LIGHTS, FLAMES, SPARKS, HEATERS, SMOKING, ELECTRIC MOTORS, STATIC DISCHARGES OR OTHER IGNITION SOURCE DISTANT FROM THE HANDLING POINT”

          My recommendation is to only use the product on the outdoor compressor coils. A different cleaner is needed for the indoor air handler evaporator coils.

          WEB Coil Cleaner does have favorable user reviews on Amazon.com:

          • Derek January 4, 2014 at 6:16 pm #

            What cleaner should I use for my indoor evaporator coils?

            • BobJackson January 5, 2014 at 10:53 am #

              I understand the confusion now. The Frost King brand no-rinse cleaner has been discontinued. The new brand made by the same company is the Thermwell Products AC-Safe Air Conditioner Coil Foaming Cleaner. See the update with product links in How to Clean AC Evaporator Coils – Part 2.

  15. Steven Swann July 22, 2011 at 4:44 pm #

    Bob:

    You start by asking if the filter in the AC unit (shown in your pictures) should be changed.

    You go on to explain how to change the coil, but don’t answer the question about the filter on the air handler.

    Should it be changed? Monthly?

    Thanks,

    Steven

    • Bob Jackson July 22, 2011 at 6:32 pm #

      Change the filter monthly as a rule.

      But… I have Honeywell touch screen thermostats in my home. The Honeywell keeps track of the total run time since the AC filter was last changed and displays a “Change Filter” message after 10 running days. This is about every 2 weeks in July/August and January/February in the Atlanta area where I live. Much longer when the weather is mild and I have the windows open in the Spring and Fall.

  16. Felice July 25, 2011 at 10:32 am #

    Hello, the air in that my chiller unit blows out is moist and not
    very cold. At around 9pm the temp. inside is about 75 degrees, and
    the thermostat i put at 70, hoping to cool down the temp. to no avail.

    As i understand it, my chiller unit in my condo unit takes cold liquid from the main
    boiler room which is about 40 yards away in another building and somehow
    is brought to my unit’s hvac.

    It appears that a square, about 24×24, 1-inch-deep filter filters in-coming air,
    which passes through a set of fins, which are very close above
    a pan that catches water, the “filtered” air is aspirated by
    a fan/blower that pushes the filtered
    air up
    into another set of coils(?) maybe? these i cant readily access it appears to me.
    Im told that the air is cooled as it goes over these coils.

    What can i do to see the inaccessible coils?
    the first, accessible set of coils seem to be clean
    as i can see all the fins and spaces between them…Thank you
    for any help and your time.

    • Bob Jackson July 25, 2011 at 7:24 pm #

      Based on your description – “main boiler room … 40 yards away” you most likely have a “fan coil unit” that circulates a glycol & water mixture pumped from the chiller unit (a.k.a. “main boiler room”) to your condo. Are there 4 equal size insulated copper pipes going into your condo air handler unit? This is a sure indicator you have a fan coil unit. Two pipes are the chilled water supply & return for cooling; the other two are the hot water supply & return for heating. Since you see two sets of coils, I believe you have the 4 pipe system. (Some systems have only 2 pipes and the water flow is reversed for heating and cooling.) I also expect your monthly bill is the total cooling or heating cost divided equally by the total number of condos. That is, your monthly bill is always the same as your neighbors.

      The insulated cold water supply pipe coming from the chiller (boiler room) should be in the 44 degree F range as it enters your fan coil unit in the condo. The cold water supply copper pipe should be “beer can cold” and sweat with condensation when exposed to the room air, if not, this could be your problem. Perhaps you have a malfunctioning chilled water control valve on your fan coil unit? Or a bad thermostat, which signals the control valve to open and close allowing the chilled water to flow through the coils.

      Dirty coils could be blocking the air flow and need cleaning. Fan coil units are available in many different configurations, some fan coils look like residential air handlers, however I’m unable to provide specific guidance on how to access your coils. You might be able to Google the owner’s manual or parts diagram for your unit using the manufacturer name and model number for insights.

      My recommendation is to call a HVAC company to inspect your unit for a bad control valve, check the thermostat and condition of the coils. My bet is you have a problem with the control valve.

  17. Felice July 27, 2011 at 10:42 am #

    “Jackson” Thank you for your understanding, info, insight…

    yes the unit in has two, insulated, about 2-inch pipes
    near the bottom of the hvac unit, that go into it…
    the blower fan works and comes on and off but
    it does it very many times. i believe because
    the air it’s blowing out is rather moist/humid, as i mentioned.

    it seems that the large blower/fan needs to be detached and
    above it i would be able to access the condenser or evaporation
    coils….monthly bill is included in the monthly condo fee
    The hvac unit is a “gw bohn heat transfer division”
    Again thank you for any insights and your help…

    • Bob Jackson July 28, 2011 at 7:02 am #

      > it seems that the large blower/fan needs to be detached and
      > above it i would be able to access the condenser or evaporation coils
      I think your air handler (fan coils) are an updraft model similar to this diagram.

      > The hvac unit is a “gw bohn heat transfer division”
      GW Bohn is now owned by Heatcraft. You may be able to find information on your unit by searching their web site for your Bohn model number.

      Please post back when you determine the problem.

      Thanks,
      Bob

  18. Colt July 29, 2011 at 8:36 pm #

    Finished with school, and just starting my HVAC career. This is a great site! I’m sure I will visit it again. Very informative. Thanks Bob.

  19. Felice August 1, 2011 at 10:03 pm #

    Jackson….hello…
    do you think the problem
    is likely from the ‘boiler room’ …that
    the liquid from there is not cold
    enough? Thank you for your help.

    • Bob Jackson August 2, 2011 at 6:29 am #

      A chilled water temperature problem (too warm) is unlikely, otherwise your neighbors would be complaining. As I wrote in my July 25 reply:

      “My recommendation is to call a HVAC company to inspect your unit for a bad control valve, check the thermostat and condition of the coils. My bet is you have a problem with the control valve.”

      To clarify, I believe you have a problem with the water control valve or the control circuitry (relay board) that operates the valve.

  20. Mike Maul August 2, 2011 at 11:32 am #

    My coils are inverted compared to your photo. The inner part is very clean and water appears there. The outer part is dry and appears to have collected pieces of the insulation from the surroundings.

    Should I be using a cleaner on the outer dry part to improve circulation/performance?

    Very nice site with the best information I’ve seen. Thanks for making it available.

    • Bob Jackson August 2, 2011 at 11:33 pm #

      I doubt the foaming coil cleaner will remove the bits of fiberglass insulation plastered to the upstream side (dry side) of the evaporator coils. Coil cleaner is a detergent and disinfectant that won’t break down fiberglass insulation mechanically wedged into the coil fins. What you need to do is get a new pump sprayer and direct a stream of very warm water from the far side (i.e. wet side) through the coils to knock off the insulation on the other side. (Don’t use a pump sprayer that’s had other household chemicals or pesticides in it or you’ll be breathing it later.) This isn’t “pressure washing”, rather it’s applying light pressure to remove the insulation. You’ll need to turn off the circuit breaker and place a pan under the coils to catch the water and protect the blower motor and other electronics from getting wet.

      If you’re *very careful*, a soft long bristle brush can be used to help remove the insulation. Go easy and check your progress because the fins are easy to bend/fold over.

      The next issue is to determine how insulation is getting blown onto the coils. Do you have a break in the plenum or ductwork? Has an insulation panel inside the air handler become loose? Is the air filter seated properly? The color and texture (pink, yellow, white, black; coarse or fine) of the insulation is usually a good indicator of where it originated.

  21. Mike Maul August 4, 2011 at 11:41 pm #

    Thanks for the information. I’ll try what you suggested.

  22. Scott August 24, 2011 at 5:07 pm #

    Great writeup. You have the refrigerant lines mislabeled on your photo. The cold (liquid) side coming in from the compressor should be the one wrapped in insulation. The gas return line should be the exposed copper line running back out to the compressor.

    • Bob Jackson August 24, 2011 at 7:54 pm #

      > The cold (liquid) side coming in from the compressor should be the one wrapped in insulation.
      Nope, the photo is labeled correctly.

      The small copper pipe carries the relatively “hot” (or at least warm ~100F) high pressure liquid coming from the outside compressor/condenser unit to the air handler evaporator coils in the attic. See Figure 1.6 on page 8 and Figure 1.9 on page 10 of the “PRINCIPLES OF AIR CONDITIONING” as to why the liquid line from the condenser is hot in relative terms (100F).

      Also see “How does air conditioning work?” by Austin Community College. The small “hot” copper liquid line in question runs from the Condenser (#2) to the Metering Device (#3) in the Austin College diagram. The Metering Device is also known as an Expansion Valve which flashes the high pressure hot liquid refrigerant refrigerant to a low pressure cold (20F) gas for circulation in the evaporator coils. The larger copper pipe is the return refrigerant gas line that is remains somewhat cold after leaving the evaporator coils and must be insulated to avoid condensation and sweating all over the attic and inside the walls.

  23. Lisa F August 25, 2011 at 6:26 pm #

    I live in a condo(all electric) and my downstairs neighbor got a bad leak. They came out and cleaned her unit and said it’s mine or the unit upstairs. My upstairs neighbor just replaced theirs and mine hasn’t been cleaned in several years. I have little money and I am very concerned. They said the water is coming from the condensation pipe that travels throughout out units. It serves us all.

    • Bob Jackson August 25, 2011 at 7:24 pm #

      So, the neighbor below your unit had water damage and the repairman says the water damage was caused by a leaking condensate from one of the A/C units on the upper floors, and you believe your unit may be the cause? Clogged condensate drain pipes are a common problem.

      An HVAC repairman can usually fix this for the price of a standard service call. Dirt, slime and algae tends to build up in the condensate drain outlet and/or pipe, causing the drain to clog, water will overflow and run down between the floors and walls. Cleaning isn’t difficult – wipe away what’s visible, run a bottle brush instrument down the pipe, blow it out with compressed air, chemically disinfect/kill the algae and rinse out the pipe, then put some time release algae inhibitor tablets in the condensate drain pan for long term (couple of months) relief. Most condensate drain pipes are PVC plastic and worst case a section can be sawed out to get access at a clog further down the pipe and replaced.

      > They said the water is coming from the condensation pipe that travels throughout out units. It serves us all.
      If the HVAC technician says your drain pan and drain is fine, then take the matter up with your condo association as a common infrastructure maintenance responsibility.

      > mine hasn’t been cleaned in several years.
      Yours may need inspection and cleaning anyway. You’ll save money on the lower electric bills when the system is tuned up and running at optimum efficiency.

      Please post back when you find the problem and how it was repaired.

  24. Justin October 15, 2011 at 1:24 pm #

    Huge help Bob, thank you very much. :)

  25. Jeff March 25, 2012 at 1:49 pm #

    is there anything that can be sprayed on a/c evaporator coils to make water sheet down them instead of water dropping off before reaching drain pan?

    • Bob Jackson March 25, 2012 at 3:08 pm #

      If your evaporator coils are clean the condensate should wick down to the condensate pan. Dirt or mold on the coils will interrupt the flow, soaking up water and providing sites for the water to drip off the coils before reaching the pan. Think of a dirt having the same effect as a stalactite on the roof of a cave.

      To your question, I’m unaware of a HVAC product – other than coil cleaner – that will repel water as your describe. Most coils are made of aluminum, which if clean won’t adsorb water to the extent that it beads up and drips off prematurely.

  26. rene June 24, 2012 at 5:25 pm #

    Looking for advice about our a/c unit. It blows cold air but the house is not cooling. The temp in the house is 10-15 degrees higher than what it’s set on. The smaller uninsulated copper tube is hot to the touch. We’ve cleaned the filter and sprayed down the outside unit and blew the dust out of the indoor unit. Husband thinks it is just low on freon. I’m fearing it’s not that simple of a solution. It’s a Trane xr 80 and less than 10 years old. Feeling desperate and afraid of a huge expense. We live in Texas and it’s hot.

    • Bob Jackson June 24, 2012 at 9:40 pm #

      Is the outside compressor unit and fan running? It’s normal for the small uninsulated copper tube to be hot to the touch – that’s your high pressure liquid line coming from the outdoor compressor that goes to the evaporator coils in the air handler.

      New Trane XR80′s have a 10 year warranty on internal parts, so your unit might also still be in warranty. Recommend calling a Trane-certified service technician. After the problem is diagnosed, he can tell you if it’s covered by the warranty or how much the repair will cost and your options. You’ll initially only pay for the service call (it typically costs less than $100) and can make an informed decision what to do next.

      Let me know when you find the problem.

  27. LBD July 6, 2012 at 9:13 pm #

    This is great info. I knew the leak around my unit had do do with the evaporator coils but had no idea how to diagnosis or fix the problem. I really hope I can fix this!

  28. bob July 9, 2012 at 8:26 am #

    I have 9 year old furnace/ air conditioner. About 4 years ago, they had to replace the a/c “A” coil due to a leak. Everything was fine for a year or 2, then we noticed the house humidity was going way up and the temp very slowly would drop. Tech checked system and said everything look fine, but also said something is not right. (?)
    There was a 14 degree difference between supply and return. said it should be 16 to 20. said refrigerant level was fine.
    This year, same thing, BUT now it seems like there is just not enough air blowing out of the registers. We change the MERV 10 pleated high capacity filter about 3 times a year. Manufacture recommends once a year.
    System looks clean, but the acess panel on the “A” coil is behing all the little valves, drier and small tubes, and the tech said you should not move them out of the way. He also said the inside of the “A” coil could be plugged up with dust, restricting air flow.
    We have several birds, and I dont want to use cleaners on the coils, since vapors can kill our birds.
    Can I just hose the “A” coil off?

    • Bob Jackson July 9, 2012 at 3:23 pm #

      Reduced airflow and high humidity could mean your AC evaporator coils are dirty with mold/mildew growing on them. The only way to really know is to open up the air handler and inspect the coils.

      Did the AC technician inspect your ductwork and air handler housing for leaks? You could be blowing cold air through a break in the ductwork somewhere in the attic. Check if the air filter housing is sealed to prevent unfiltered air from being drawn into the air handler and clogging up the coils. (I cover the filter slot on my air handler with a piece of aluminum HVAC tape.) Also check if the blower motor fan needs cleaning.

      If you’re not comfortable opening up the air handler, hire an HVAC service company to clean the coils. Ask that they inspect the coils for dirt/mold first to see if this is the problem, then clean the coils with a pump sprayer and wand filled with a mild coil cleaner solution to shoot through the coils. You’ll need to move the birds outside and air out the house for 20 or 30 minutes with the windows open and the air handler running. Wait until any scent of cleaning fluid is gone before moving the birds back inside. The issue is the coils need to be disinfected to kill the mold/mildew so it doesn’t come back anytime soon.

  29. RMS July 20, 2012 at 1:31 pm #

    Great info. I got the coils clean, and saw the comment above about the missing A frame cap. The AC works well, EXCEPT one duct that blows warm air. The duct is a single line into the distribution box (dont know what it is called) and I cant see or feel any leaks. With a thermometer I measured all other ducts air at about 60F, this one is at 80F! Could the missing cap be the problem? Anything else I should check for?

    • Bob Jackson July 21, 2012 at 9:10 am #

      If the AC vent is located in the ceiling and you’re able to trace the branch duct line in the attic back to the main trunk, then one of the following must be the problem for the warm air:

      1. A damper is blocking the air flow. Dampers can be manually or electronically controlled.
      You will need to inspect the ductwork to see if there’s a damper that’s partially closed.

      2. There’s a break in the ductwork.
      Follow the branch line from the main trunk to the ceiling vent boot, looking for taped
      joints that have separated or holes in the duct (maybe a squirrel chewed a hole?).

      3. Something is blocking the branch line duct.
      It’s possible a piece of plenum or ductwork insulation came loose and is clogging
      the branch line. If the airflow is very weak and you’ve checked everything else,
      then separate the branch line from the main trunk duct and look inside.

      4. The branch line is excessively long and/or too small, and not covered by
      attic insulation. The cold air is simply heating up on it’s way through the
      ductwork. If the branch line is only 4 inches inside diameter, more than 20 feet
      long and laying on top of the attic insulation, then the hot air in the attic
      can cause the air inside the duct to heat up.

      I’m guessing the problem is #4. The fix is to replace the 4 inch ductwork with a 6 inch diameter branch line for increased airflow to the room. Cover the branch line with a fiberglass attic insulation to minimize the cooling losses to the hot attic.

  30. jsid July 22, 2012 at 10:08 am #

    ANYONE KNOWS ANY DETAILED INFORMATIONS ABOUT: HOW TO MAKE A SMALL 8′X9″ SIZE ACCESS WINDOW??? INTO THE METAL CASE OF FRONT PANEL OF THE EVAPORATOR COIL?? please help

    • Bob Jackson July 22, 2012 at 10:31 am #

      See my comment dated September 14, 2011 at 8:08 pm in Part 2 for advice. Comments are listed in chronological order.

  31. jamie September 4, 2012 at 11:55 am #

    I’m having trouble getting the access panel door off. My refrigerant gas line seems to be sealed to the access panel door with a round seal making it difficult for me to remove the panel. Is it okay to break this seal somehow?

    Here is a picture. If you zoom in, you can see the black seal. http://i89.photobucket.com/albums/k238/honeychildjamie/gasline.jpg

    Thanks, Bob!
    Jamie

    • Bob Jackson September 4, 2012 at 7:27 pm #

      The photo helps a lot. The black seal in question is just a gasket to seal around the refrigerant line where it enters the air handler to prevent air leaks and condensation. I see that you’ve already removed the right side access panel screws. Just wiggle the access panel up and to the right. The gasket is sticky from being in place for so long.

      BTW – the HVAC tech who installed my system neglected to install the foam refrigerant line gasket. I found my gasket in the plastic bag with the owner’s manuals. To limit the air leakage, I partially sealed the access panel opening with HVAC tape.

  32. jeff November 15, 2012 at 1:13 pm #

    I did not look through all of the comments so maybe this was pointed out. You do not have a u-trap on your drain line. This allows air to be sucked back up the pipe, which is like srilling a hole in the duckwork, as well as “spitting” the water all over the place that is trying to drain.

    • Bob Jackson November 15, 2012 at 10:06 pm #

      > Jeff wrote:
      > You do not have a u-trap on your drain line.
      Hi Jeff,
      The purpose of a U-trap is to prevent sewer gases from getting into the air handler and stinking up the house, this is why bathroom and kitchen sinks have a U-trap (a.k.a. P-trap). My attic air handler condensate drain line runs to the outdoors, not to the sewer line. Therefore a trap is not required.

      > Jeff also wrote:
      > This allows air to be sucked back up the pipe…
      The blower motor on my system pushes air into the evaporator coils as illustrated in the 2nd photo of the project. This creates a positive pressure in the coil box that will not “suck [air] backup the pipe”, rather it pushes air and condensate down the drain line to the outdoors.

      The condensate drain line is in the original configuration as the HVAC system was installed; I have not modified this.

      === Reply to Jeff’s 2nd comment ===
      > Jeff wrote:
      > One more thing. The incoming cold liquid line should also be insullated to retain the “chill”.

      What you describe as the “incoming cold liquid line” is incorrect.

      The refrigerant liquid line is very warm-to-hot as it leaves the outdoor compressor unit; a result of compressing a gas to a liquid. There is no “chill” on this side of the refrigeration cycle; place your hand on the copper tube and you’ll feel it’s quite warm. This is why it’s an uninsulated copper tube all the way from the outdoor compressor to the attic air handler because warm lines don’t cause condensation and sweating.

      The refrigerant liquid line was installed this way when the home was built and is the standard method of doing so; I have made no modifications or given advice to make changes to the liquid line in the project.

  33. jeff November 15, 2012 at 1:14 pm #

    One more thing. The incoming cold liquid line should also be insullated to retain the “chill”.

  34. Andre Baran December 26, 2012 at 5:31 pm #

    Question please for Bob Jackson,

    Sir, you published a picture of your air handler/evaporator coils back in 2009 and claimed that the unit was 9 years old. You pointed out the rust on the frame and some discoloration on the copper tubing. I had a Carrier unit installed 2 years ago and after about a year and a half started noticing rusting condensate coming out from my pvc drains. Looking inside I was shocked to see my 2 year old air handler look almost as rusty as your 9 year old one. I am worried that this is premature deterioration but my A/C company does not want to pursue it and claims that my cleaning of my drains with bleach may be partially responsible. Any ideas or suggestions? The unit is in my garage in Florida but my prior 14 year old Trane unit did not appear significantly more rusted than what I see now.

    • BobJackson December 27, 2012 at 12:58 am #

      Hi Andre,
      Rusted end plates on evaporator coils are typical because manufacturers use steel for this part. The end plates are themselves are just supports for the copper tube and aluminum fin coil pack. I’m uncertain if the end plates rust because water condenses on the chilled metal and/or galvanic corrosion at work due to contact between dissimilar metals (steel end plates and copper tubes). I’m leaning towards water condensation being the main cause for rusted end plates.

      Rusted evaporator coil end plates are unfortunately common:
      * Rusty evaporator…anything that can be done to slow?
      * Excessive rust on evaporator coil?
      * 14 month old Trane rusting

      The above links are by HVAC-Talk.

      Rusted end plates don’t necessarily mean the evaporator coils are leaking refrigerant, especially if the aluminum fins and copper tube packs are corrosion free.

      Take a look at this slides 4 to 8 of this Evaporator Coil Assembly presentation for a general overview.

      Better evaporator coils such as the Trane All-Aluminum Comfort™ Coil feature all aluminum coils, including aluminum end plates and tubes. The inner coil panels are painted to resist corrosion and can be removed to access the inside of the coils for cleaning. This article illustrates the difference between the Trane All-Aluminum versus copper/steel coils after a 500 hour salt spray test.

      While I not owned a Trane All-Aluminum Comfort™ Coil unit, I had an old AC system at my former home in Florida replaced with a Trane XL 16i system and was very happy with it.

      If you want to do something about the rust on your evaporator end plates, paint the end plates with COLD GALVANIZE Corrosion Inhibitor. COLD GALVANIZE is very high in zinc which acts as a sacrificial anode, protecting the steel from rust. Turn off the AC system, open up the air handler to expose the coils, wait until the end plates are completely dry, be careful to protect the air handler cabinet and coil fins from overspray and apply the COLD GALVANIZE Corrosion Inhibitor, allow it to dry, then close up the air handler. I would only do this if your system is past the manufacturer’s warranty or before installing a replacement coil at your own expense. If your system is still under warranty, hire a licensed HVAC technician to do it for you if he says it won’t void the factory warranty. However, you will only be able to access the outside face of the steel end plate so it’s only addressing part of the rust issue.

      All said, I would let the rust be and buy a better designed system when the time comes.

  35. Scott March 18, 2013 at 4:48 pm #

    I m about to clean my Evaporator Coil in my air handler unit as I think it is the cause of a very bad smell coming out of my AC vents.

    My question is:

    Why is this smell only evident when I turn on the AC? The heater has no bad smell when turned on and the airflow should be going over the same equipment. It is that the heater is blowing moist air over the coils and thus mildew and such is building up and when the coils are active in when the AC is on, that is when the smell gets permeated to the airflow?

    Thanks in advance.

    • BobJackson March 18, 2013 at 5:19 pm #

      The bad odor is noticed when the AC is on because water condenses on the chilled coils, wetting the coils and condensate drain pan. Some of the condensate evaporates and is blown out the air vents, taking the bad smell/odor along for the ride. For an analogy, what smells worse: a dry or wet dog? :-)

      When you clean the evaporator coils, also check the condensate drain line is not clogged.

  36. Mark Robinette June 22, 2013 at 10:48 am #

    Thank you so much for such an informative site!

    I’ve got a three year old system (in a 33 year old house). Past several months, my allergies have been off the chart. There is a progressively worse moldy odor coming from all registers every time the unit cycles. Was able to get the sheet metal front off the A coils and found the coils to look clean and the drain line is open. Went ahead and used some no-rinse coil cleaner I had on hand. Although tight quarters, I shined the light further up into the plenum and found that the fiberglass insulation that is glued to the walls of the plenum were wet and covered in mold!

    Was able to cut a scuttle hole in the side of the plenum, about 10″x20″. Covered the top of the A coils with a towel and used a large scraper to scrape the damp, molded fiberboard insulation from the sides of the plenum leaving it temporarily uninsulated. Wasn’t able to access the upper distribution box to see if that fiberboard insulation is damp also. I’ll save that for next weekend.

    Question – what on earth is causing the wetness inside the plenum box? I crawled the entire length of the attic, all ductwork is good. I don’t have any damper issues. All registers are blowing the same volume they always have. All ductwork is well insulated and no breaks or obstructions. I’m stumped!

    • BobJackson June 22, 2013 at 4:53 pm #

      > Question – what on earth is causing the wetness inside the plenum box?
      Hard to be certain why moisture is condensing inside the plenum box. Just to be sure, mold was growing inside the plenum box and not the foil faced insulation inside the sheet metal coil case?

      Are you certain it was mold growing on the plenum duct board? The airstream surface of rigid duct board is often coated with a moisture resistant black mat, which could look like a dark mold layer on the yellow fiberglass substrate.

      The condensation may be caused by water droplets being blown off the evaporator coils, especially if the coils are partially clogged on the underside, or upstream side where it’s difficult to see, creating localized higher than normal air velocity in the unclogged areas. Wide rivers run slow, narrow rivers run fast (Bernoulli’s principle).

      Whatever is causing the condensation in the plenum box, the best way to deal with mold is:
      * Verify the evaporator coils are clean inside and out, and nothing is obstructing the air flow.
      * Check the humidity level in the home. If the humidity is greater 50% in the summer with the A/C running, then something may be wrong. It could be the A/C unit is over-sized (big blast of cold air, but doesn’t run long enough to lower the humidity), undersized (can’t keep up with the load) or the system needs a tune-up (low refrigerant, dirty compressor coils, dirty evaporator coils, etc). The EPA recommends less than 60% humidity in the summer to for comfort, limit condensation and mold.
      * If you see mold in the plenum box or evaporator coil case insulation, turn off the system and let it dry out. Spray down the moldy insulation surfaces with Lysol to kill the mold. Wait until dry, then vacuum the rigid duct board with a brush attachment. Take care not to touch the evaporator coil fins, which bend very easily.
      * To prevent mold from recurring, install a ultraviolet air treatment system in the plenum box. The UV light kills mold and bacteria.

      Also recommend calling a licensed HVAC technician for an expert opinion about your system, since every situation is different.

      This Honeywell UV Treatment System kills mold on evaporator coils and inside plenums:

      Product literature and installation guide: Honeywell UV100A1059/U Ultraviolet Air Treatment System.

      A reasonably accurate and not too expensive digital temperature and humidity hygrometer/thermometer:

    • BobJackson July 7, 2013 at 10:25 am #

      Follow-up to my original reply on June 22, 2013 that suggested an Ultraviolet Germicidal Light (UVGI) to prevent mold growth. I liked the idea and installed a UV light coil treatment light in my air handler as detailed in this project.

      > Question – what on earth is causing the wetness inside the plenum box?
      Two additional thoughts: Make sure the plenum box is well insulated and the relative humidity is 50% or less in the house.

      Let me know if you’ve solved the problem.

      Thanks,
      Bob

  37. Yash June 25, 2013 at 1:30 pm #

    Hello,

    My attic ac is not generating any water! ! ! I am not seeing any water drain to the pipe and I am also noticing that I am not having sufficient cooling at the second store of the 2 story house. I have technician checked the pressure and the freeon pressure is correct. Does this mean I need to clean the coil?

    Thanks,

    • BobJackson June 25, 2013 at 6:14 pm #

      Since the HVAC technician checked the refrigerant pressures, this means the compressor unit is OK; i.e. the compressor motor and circulation fan are operating properly.

      The HVAC technician didn’t inspect the air handler (evaporator coils, blower motor, condensate drain, electronics, etc.) while he was there?

      Since the compressor unit and refrigerant levels are good, do the following:
      * Inspect the air filter. If it’s really dirty, then it will block the air flow and the evaporator coils may ice up, hence the no condensate (not generating water). Change the air filter if has been changed in 30 days.
      * Turn on the AC for 30 mins.
      * Locate several air vents near the air handler. Is there a strong and cold air flow from the vents?
      If the air flow is weak, the evaporator coils may be dirty/clogged, you could have a bad blower motor or there could possibly be a large air leak in the duct work.
      * Turn off the AC at the thermostat.
      * Open the evaporator case panel.
      * Are the evaporator coils iced up or dirty inside or out? Use the flashlight and hand mirror technique to look through the coils for dirt/mold on inside the coils. Ice on the coils means there is insufficient air flow through the coils, which causes the coils to get too cold and ice up. The evaporator coils are a heat exchanger; the cold refrigerant inside the coils is warmed by the air blowing through the coils which prevents the condensate water from freezing on the coils; likewise the coils cool the warm air from the house.
      * While you’ve got the coil case open, check the condensate drain pan and drain pipe for clogs.

  38. Kasia June 27, 2013 at 5:18 pm #

    Hallo Bob,
    I have a huge problem. My A/C stopped working last night. It is only 03:15 pm and temperature in my place is over 80.
    The unit is running outside but inside everything is dead silent. Please advise me ASAP. I am afraid that since I don’t know anything about A/C and don’t know any A/C techncian that I might be charged for something that does not need to be repaired. Would you have any idea what could cause my problem and how expensive could be the repair?

    • BobJackson June 27, 2013 at 7:28 pm #

      If the indoor air handler isn’t working, check the following:
      * Check the circuit breaker; the outdoor compressor and indoor air handler are normally on the same circuit breaker, so it’s unlikely this is the problem but yours might be on different breakers.
      * There’s normally a secondary power shutoff switch by the air handler, it looks like a light switch mounted near the air handler. Check that it hasn’t been inadvertently switched off.
      * Has the condensate safety overflow switch been activated? Depending on the configuration of your AC system, it might be the condensate drain pump isn’t working (this happened to me) or an overflow switch on the gravity-flow drain pipe located near the air handler. However, if the safety switch is tripped then it should shutoff both the outdoor compressor and indoor air handler, so I doubt this is the problem.

      Otherwise, you’ll have to call an HVAC technician because the air handler blower motor, motor capacitor or control circuit electronics are bad.

      The cost of a service call to diagnose what wrong will be in the neighborhood of $80 to $150 (call around as rates vary). A bad blower motor capacitor would be the least expensive to replace.

      Meanwhile, turn off the AC until it’s repaired.

  39. Jim July 9, 2013 at 7:18 pm #

    Hey Bob,
    We have some kind of leak from where the coils are stored. I’m not sure if a pan is broken or the drain pipes are blocked. The front panel on mine has a type of metal tape with some type of putty behind it. I’m afraid to take it off because I might damage the unit further. Should I have a air conditioner repairman come out or just try breaking it all down myself? How much do they usually charge to replace or repair something like that?

    Thanks,
    Jim

    • BobJackson July 9, 2013 at 7:43 pm #

      Since you’re concerned about opening up the coil case yourself, I’d call the air conditioner repairman. Call two or three HVAC repair companies and ask what they charge for a diagnostic visit. My guess is between $75 to $150. The cost of the service call is usually credited towards the repair cost, if repair work is needed.

  40. Colin August 3, 2013 at 1:04 pm #

    Hi Bob,

    Thanks for all the help. In addition to cleaning the evaporator coil I also needed to clean the blower fans. I took apart the motor, fan and housing and cleaned them all, but am running into trouble putting them back together. There’s no clearance between the fan and the housing when I screw the motor back into the housing, preventing the fan from moving freely. To make matters worse, now when I try to take the motor back out of the fan to realign, I can’t! It’s stuck. Am I missing something? The motor is a Dayton 3LU83G. Thanks in advance.

    • BobJackson August 3, 2013 at 4:14 pm #

      What is the make and model # of your air handler? The air handler service manual is often available online which may have service instructions. Whatever you do, don’t force the parts together because it’ll make matters worse. You may need to call a HVAC tech to reassemble the blower unit.

  41. Anil August 17, 2013 at 8:51 pm #

    Hi Bob,
    The drain pipe from my evaporator coil unit seems blocked causing condensate to be overflowing into the adjacent housing for the computer control/ motherboard and then dripping from the seams below. Unfortunately, I am unable to clean the drain pipe as the previous installer had glued a plastic elbow to the outside of the drain pipe and attempts at unscrewing have resulted in the entire drain pipe rotating freely without it coming off. If I am apprehensive of opening the unit and instead first try and cut the drain pipe to try and flush it clean, can I then get another piece fitted in to allow drainage and how would I be able to do so? Will that necessitate opening the coil unit anyway? A tech. I had called said that it would require the entire coil to be changed as rusting of the collection tray inside would have caused the drain to block. Can just the collection tray be changed?
    Thanks.
    Anil

    • BobJackson August 18, 2013 at 10:49 am #

      > Unfortunately, I am unable to clean the drain pipe as the previous
      > installer had glued a plastic elbow to the outside of the drain pipe
      The AC evaporator coil condensate drain (or “drip pan”) typically has a 3/4″ MPT (Male Pipe Thread) PVC connector. MPT fittings are also known as National Pipe Thread (NPT), which just means it’s a standard threaded fitting available at home improvement stores.

      The threaded end of the 3/4″ PVC MPT fitting screws into the condensate drain pan (hand tight only!) and 3/4″ PVC drain pipe is glued (solvent welded) to the other side of the fitting. You can see the 3/4″ PVC drain line fitting at the lower right of this photo.

      See Figure 2 on Page 3 of these evaporator coil installation instructions for a representative condensate drain pan connection diagram.

      > and attempts at unscrewing have resulted in the entire drain pipe rotating
      > freely without it coming off.
      You’ll need to remove the evaporator coil case access panel to see the other side of the condensate drain pan connection. If you have a metal drain pan without a factory made drain adapter (molded plastic module) there’s may be a hex nut and rubber washer inside the drain pan that’s spinning and preventing you from unscrewing the 3/4″ PVC MPT drain fitting.

      > If I am apprehensive of opening the unit and instead first try and cut the drain pipe to
      > try and flush it clean, can I then get another piece fitted in to allow drainage and how
      > would I be able to do so? Will that necessitate opening the coil unit anyway?
      Opening the coil case to see what’s preventing you from unscrewing the 3/4″ threaded drain fitting is necessary to figure out if:
      * A threaded nut spinning inside the drain pan is preventing removal of the threaded drain fitting.
      * If the drain pan connector is possible broken.
      * What’s clogging the drain line. Rust, dirt, mold or other debris.
      * If you have a severely rusted and leaking metal condensate pan.
      * Condition of the AC evaporator coils.

      Should the 3/4″ PVC drain pan fitting need to be replaced, you’ll probably find it easiest to saw the PVC drain line a foot or so downstream of the evaporator coil case to remove the threaded drain pan fitting and elbows because there may not be room to install a 3/4″ PVC straight connector at the elbow. The repair consists of gluing on a 3/4″ PVC straight connector on the old pipe where it was cut then measuring and installing new pipe, elbow(s) and threaded drain pan fitting to match what was removed. The cost of the PVC pipe and fittings is less than $20. The PVC purple solvent/cleaner and glue is maybe $10 or $15. If you search this site for PVC (see top right of the page for the search box) you’ll see many examples of PVC plumbing projects.

      > A tech. I had called said that it would require the entire coil to be
      > changed as rusting of the collection tray inside would have caused the drain
      > to block. Can just the collection tray be changed?
      A metal drip pan can rust which besides blocking the drain line will also leak onto the furnace and blower motor, eventually filling up the secondary drain pan causing the safety cutoff float switch to activate and shut down the unit to prevent flooding.

      The collection tray (drip pan or condensate drain pan) can be changed, however it requires draining the refrigerant, cutting the copper refrigerant lines and removing the evaporator coils. The work costs hundreds of dollars and at that point, it’s probably cost effective to replace the AC evaporator coils with a new & improved unit. I’d go with a “cased coil” unit meaning it’s a complete insulated sheet metal coil case and evaporator coils. My A/C unit is the “cased coil” type. An uncased coil is just the A-frame coils and drip pan assembly.

      You can send photos of your unit to bob (at) handymanhowto.com if you’d like additional advice.

      Recommend you have an HVAC tech take a look at your unit. A service call usually runs $75 to $85 and he can tell you what’s the problem, clean the drain line and make PVC drain line repairs which usually aren’t expensive for what you described. The HVAC tech will also have special drain line suction equipment to remove any downstream clogs. If your drain pan is in really bad shape, he can provide a replacement estimate so you can budget for the work.

  42. Kathy March 27, 2014 at 7:25 pm #

    I’ve had issues with my HVAC system since moving into my house, which was built in 1998, although I’ve lived in it 5 years.

    I live in a suburb of Phoenix, Arizona, so run the air conditioning for many more months than I would living anywhere else. I am sure there are leaks in my flexible ductwork, in addition to other problems, but the ducts are located in the attic and I cannot find a single HVAC company that will check them.

    While every company I’ve talked to, about 10 of them over the years, wants to sell me a new system and an air cleaner, etc., not one seems to be concerned that my air handler has no drain line (I don’t think they know what it is), and that in the part of the inner flex ductwork I can reach when I take off the grilles/vents, there appears to be a black powder — like soot — even though I have no fireplace. There’s a lot of it stuck in the folds of the flex duct, so I don’t think a duct cleaning would remove it.

    I just don’t know what to do. Would you happen to know of any honest people or companies in my area? Should I just ignore it? Move? I planned on having this house for the rest of my life, but with filters full of gray and black “dirt” when I change them monthly, I’m not so sure.

    • Bob Jackson March 27, 2014 at 9:22 pm #

      > not one seems to be concerned that my air handler has no drain line
      An air conditioner not only cools but also removes moisture from the air to lower the humidity. The moisture in the air condenses on the cold evaporator coils and a condensate drain line is required to take away the water from the drip pan. If your A/C system really doesn’t have a condensate drain line (gasp!), that black powder could be dried mold that’s blown off the evaporator coils and settling in your ductwork.

      > Would you happen to know of any honest people or companies in my area?
      You can find reputable air conditioning service companies on Kudzu.com with uncensored consumer reviews. Best of all, Kudzu.com is free and doesn’t require an account. For example, a Kudzu.com search for “air conditioning repair” in Phoenix, AZ lists several good candidates.

      Call two or three A/C Service companies, explain the problem and that you want them to:
      * Perform a regular A/C system maintenance: Check the electronics, motor start capacitor, refrigerant charge, temperature drop across the evaporator coils, change the air filter, check the safety cutoff float switch, etc.

      In addition confirm that you want them find the source/cause of the black powder:
      * Verify your system has a condensate drain line and the line is not clogged.
      * Unclog and flush the drain line and drip pan if needed.
      * Open the evaporator coil case and clean the coils.
      * Check the attic supply and return ductwork for breaks and leaks.
      * Find the cause of the black soot; whether it’s mold or dirt from unfiltered air being drawn in from a break in the ductwork.

      Follow the HVAC technician around and ask questions. I had my A/C system serviced today and the tech was more than happy to answer my questions, show me the capacitor test readings, look inside the system, show me the gear he has in the van, explain why the humidifier control was wired incorrectly (he corrected it), various repair costs, upgrades and options. Most techs take pride in their work and enjoy when someone takes an interest. Just be nice and give the tech space to work.

      You might consider the 5-Minute Home Mold Test kit on a sample of that black powder:

      Let me know when you fix the problem.
      Thanks,
      Bob

  43. Kathy March 28, 2014 at 8:33 am #

    Thank you so much for all this great information, Bob. I think a big reason that guys from the various HVAC companies are reluctant to check the ductwork and air handler is because they are in the attic. The air handler is easy to reach and to see and I have asked many of these guys about where the pan is and whether there is a drain line hidden somewhere that should be drained and they just tell me that this air handler doesn’t have anything like that.

    They treat me like I’m really stupid, but I have done more research on these split units and various parts and connections, etc., than it seems they have.

    I have a split system, with the compressor unit outside. I don’t know if that makes a difference.

    Anyway, thank you again for replying so quickly. If you like, I can update you (so you can update readers) on the companies I find and if any of them know what I’m talking about. If there isn’t any company in Phoenix that can do what is required, then that’s a huge business opportunity out here for someone who can.

    Thanks again.

    Kathy

    • Bob Jackson March 28, 2014 at 8:45 am #

      What is the make and model # of your air handler? The manufacturer installation guides can usually be found online. While you do live in an arid desert climate a condensate drain line is still needed. Your split system configuration with an indoor air handler and outdoor compressor unit is very common.

      It shouldn’t be a problem having the A/C service company do a proper inspection and crawl around in the attic if you specifically make the request. You should expect to pay more compared to a routine service call.

      Please do write back when you find a company you’re happy with and resolve the problem. I’m always happy to give a shout-out to a job well done. You can also post feedback on their Kudzu.com page.

      Thanks,
      Bob

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