In the early 1990′s, I bought a home in south Florida and did the usual routine of hiring a Home Inspection company. Home Inspectors are worth every penny and among the many items they examine, will check the heating and cooling operation of the air conditioning units – air temperatures and general condition of the unit. You should confirm in advance the Inspector will open up air handler to check the condition of the blower fan, evaporator coils, drain pan, etc. The Home Inspector that I hired back then didn’t open up the air handler and I wasn’t knowledgeable enough back then to ask about it.
When buying that home in south Florida, I made the expensive mistake of not hiring an air conditioning technician to open up and inspect the air handler before I purchased that home in south Florida. Rather, I hired an A/C company to check the unit after I closed the deal and was moving into the home. When the A/C technician opened up the air handler he called me over and said the unit had never been serviced and was a mess. The evaporator coils were covered with mold, heavily rusted and leaking refrigerant. I had the A/C company replace the entire air handler that very day to the tune of $1,700.00.
This is the attic air handler in my current home.
Attic Air Handler – Furnace and Air Conditioner Evaporator Unit
Having learned my $$$ lesson, I always hired a Home Inspector and a HVAC technician to inspect a new home and the HVAC system.
Air Conditioner Routine Maintenance
Routine inspection and maintenance is very important to catch problems and save on your electric bill. I recommend hiring an HVAC technician to inspect and maintain the 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 touchscreen 7-day programmable digital thermostats by Honeywell that reminds me when it’s time to change the air filter. A dirty air filter will drive up 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 and condenser coils. If you’re not comfortable in doing this yourself, at least you’ll know when to call a professional.
Attic Air Handler
This is a the 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:
- Blower motor – bottom
- Gas furnace – center
- 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.
Click on the image for a full size view.
Attic Air Handler
Remove the Evaporator Coil Access Panel
Before you begin, turn off the A/C at the thermostat.
This is a closeup of the evaporator coil access panel. It’s held in place by nine 1/4 inch sheet metal screws and sealed along the bottom with metal foil tape.
Evaporator Coil Housing
Remove the access panel screws with a socket wrench and peel away the metal foil tape along the panel edges (if any).
Removing the Access Panel Screws
The access panel is removed exposing the air conditioner evaporator coils. The evaporator coils are basically a heat exchanger, cooling the air inside the house and transferring the heat to the outside condenser unit.
Evaporator Coils and Access Panel
A-Frame Air Conditioner Evaporator Coil
My 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
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:
- 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.
- 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 Part 2.
Take care,
Bob Jackson
Copyright © 2013 HandymanHowTo.com Reproduction strictly prohibited.
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.
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
if i use the frost king cleaner in the winter, will i need to rinse?
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.
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.
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.
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..
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.
Thanks for a well written DIY article and good pictures to help illustrate what is involved.
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.
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.
Thanks for the advice Bob, I’ll definitely check into it further.
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
The evaporator coils cannot be removed for cleaning because the refrigerant lines are permanently connected and would have to be cut.
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.
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.
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.
It’s a buyer’s market, look for another home.
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
> 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.
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!!
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.
to clean the coils, all i do is spray them with a cleaner or wipe down as well after spraying?
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.
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
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.
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.
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 come 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.
“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…
> 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
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.
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.
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.
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.
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.
Thanks for the information. I’ll try what you suggested.
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.
> 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.
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.
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.
Huge help Bob, thank you very much. :)
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?
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.
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.
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.
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!
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?
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.
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?
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.
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
See my comment dated September 14, 2011 at 8:08 pm in Part 2 for advice. Comments are listed in chronological order.
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
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.
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.
One more thing. The incoming cold liquid line should also be insullated to retain the “chill”.
> 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.
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.
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.
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.
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.