Disassembling ducting to access evaporator coil


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Old 08-01-16, 03:53 AM
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Disassembling ducting to access evaporator coil

As the title says, I would like to disassemble the rectangular ducting to access my AC evap coils to clean them. The house is 14 years old and I've owned it for 12 and I've never done this before. I'm including these photos to better explain hoping that my assumptions are correct.

Picture of the front where I need to access:
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Left side view:

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Right side view:
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I'm not an HVAC guy obviously, but I've done a bit of research so hopefully I use the correct terminology. First I believe that I need to remove the section of ducting shown in the front view photo that is below the drive connection (essentially the panel right above the furnace). The section at the back is bent into a U shape and the front section is held to the back section with a "button lock" on each side as you can see the seams from the left and right view of that section. I have confirmed that the back section is U shaped because there are no seams on the back corners (one continuous piece), just at the front corners. So to remove it, I believe I have to remove the round section (furnace exhaust pipe) that is in front of it. Then I'd remove the drive by bending out either end and sliding it off. Then I would have to pry the section out to release the "button locks" on each side. This would open the front of the ducting and allow me to access the evap coils from underneath which is presumably the dirty side of the coils.

First off, is my assumption that I have to remove the section in the front correct? I've based this on the fact that the coolant intake and return lines (not shown in the photo) are in the section of ducting above that. Plus the drain hose for the drip tray is in the section above it as well which is shown in the picture. So presumably the evap coils are in the section of ducting directly above the section I wish to remove. Is this a correct assumption?

Next is my procedure for removing the section in question correct? It looks to me that once the drive is pulled, I can pull the section straight back (once the furnace exhaust pipe is out of the way) and open the ducting.

Lastly I am pretty sure I'll need to remove the furnace exhaust pipe to remove the section of rectangular ducting, at the very least to have easier access to the coils once the section is removed. The question I have is turning off the pilot light good enough to eliminate gassing myself with exhaust? Or should I use the gas shut off valve (yellow valve on the front view) to accomplish this? If I use the gas shut off, will the pilot light be more difficult to relight?

I hope I have been clear enough and the photos I've provided are clear enough. I thank all who assist with information in advance.
 

Last edited by PJmax; 08-01-16 at 07:11 PM. Reason: reoriented pictures
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Old 08-01-16, 04:07 AM
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Welcome to the forums! You should be able to access the coils by removing the front top panel of the unit. There is nothing in the plenum chamber associated with the coils. Have you removed that panel, yet?
 
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Old 08-01-16, 04:25 AM
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Sorry are you referring to the outside unit and the condenser coils?

I haven't removed the panel in question yet as I need some confirmation as to my technique and whether I have the correct panel.

The evaporation coils (A coils) should be located in the duct work direct above the furnace should it not? This is where the refrigerant intake and return lines come into the duct work.
 
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Old 08-01-16, 04:39 AM
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I'm not sure if I'm explaining my self correctly. However I found this thread which I believe is similar to my question. If you look at the photos the OP provided at the bottom of the thread, I think this is what I'm expecting to see once I remove the panel in question. Here is the link:

Furnace coil cleaning question? - Home Improvement | DSLReports Forums
 
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Old 08-01-16, 10:19 AM
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Your installation is using what is called an "uncased coil" and it is encased in the regular plenum/ductwork. They obviously made no provisions for inspecting and/or cleaning the coil, a cost saving measure in the installation.

You will find it difficult to almost impossible to open that duct/plenum without major surgery.
 
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Old 08-01-16, 10:41 AM
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So are you saying that pulling apart the duct work where I have indicated won't expose the underside of the coil? or are you saying my approach to pulling the panel I've indicated won't work?
 
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Old 08-01-16, 11:01 AM
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Just a quick thought, but I am wondering what the orientation of the coils will be. If the green hose is the drain line, how is the drip pan situated within an upward air flow stream? Maybe the coils are vertical and air flows sideways through it, then turns upward again.
 
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Old 08-01-16, 11:34 AM
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Not sure, I'm hoping to get the panel in question off this afternoon and then take some pictures. I assumed it would look like the link I included below.
 
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Old 08-01-16, 11:49 AM
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I saw the pics in the link after I posted. I'd be interested in seeing what yours looks like. Always good to know the different ways things get done.

If your plan to remove the duct section doesn't work, I'd say use tin snips to cut a rectangular hole in the front (behind the furnace flue) then remount it using some backing plates and sheet metal screws. Then seal it with foil tape.
 
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Old 08-01-16, 01:04 PM
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I got the drive out, but I'm having trouble removing the panel. I would presume the button lock / snap lock isn't meant to pull out once it's been inserted. Is there a special tool for this? Or is it something that just can't be done? I thought if I could slide a piano wire or something down in along the inside of the lock, I could open it enough to get the buttons past the lock. I've seen an explanation on how to get it apart, but it only seems feasible on sections that are connected to another section above or below it and you can slide them apart.

I can slide the panel up, but only so far as the button flange comes in contact with the ducting above it, so I can't slide it out.
 
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Old 08-01-16, 02:05 PM
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OK, well I modified my piano wire idea and used a straightened out coat hanger. I slide it down the lock channel and it freed the panel. I won't say it was easy, but I managed it without bending the panel overly much. I will probably tweak the lock channel before I reassemble it just so everything is tight. Here are the pictures of what I'm seeing:

Front view panned out:

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Front view close up of heat exchanger:

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Two coil views:

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I hope those photos are clear enough.

Now looking for advice on cleaning the coils. First I think laying something over the heat exchanger so that the crud doesn't fall down into the furnace would be a good idea. Maybe even tape some plastic inside. Then I was thinking of starting with a vacuum and bristle brush and attempt to remove most of the crud that way.

Any suggestions for a liquid cleaning? I've read that caustic cleaners aren't good, plus you don't want the fumes of that cleaner getting blown around in your house when you resume using your AC. Looking for a few options as I don't know what will be available locally.
 
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Old 08-01-16, 07:02 PM
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I would start with a shop vac and a brush attachment. Some green coil cleaner would probably work on that coil since it only looks like a dirty drier filter. a small brush would help for the corners.
 
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Old 08-01-16, 07:17 PM
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One thing to keep in mind while cleaning is to not damage/bend the fins.
 
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Old 08-01-16, 07:22 PM
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Those fins are like hundreds of sharp knives. They can cut your hand. Some gloves might be a good idea.
 
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Old 08-01-16, 07:43 PM
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So here are the results thus far:

This was my solution for protecting the furnace from all that gunk:

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Here is the pile of stuff I got off of one side of the A coils:

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Gross, it was terrible.

This is the final bit that I was able to do with a toothbrush:

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After cleaning I could see that there was some smashed fins at the top. I didn't do this as I was unable to get the shop vac up this high, I had to use a toothbrush up there. So my plan is to get a fin comb and comb them out. Actually I've partially corrected it already with a plastic picnic knife. So I should be able to get a fin comb through it easier now. This should also help clean it some more I would think. I had planned on getting a set of combs anyway as my condenser fins are very bad.


Then I was thinking I could use some what mixed with some mild detergent. Any suggestions on the detergent. Would distilled water be better than tap water? My plan is to use a squirt bottle. I am a little concerned that I won't be able to clean out the drip tray as there is no way for me to get to it, so hopefully the liquid I use to clean with drain correctly.
 
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Old 08-01-16, 08:36 PM
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Hey Houston204, is that green coil cleaner that you linked to safe to use inside? I see that we have a Ecco Supply here in my home town (Medicine Hat) and they list it in their catalog. I'm hoping they have the combs I need too. I know the condenser fins are 20 / inch, but I'm not sure what the evap coils are. I do know that the fin density is much less than the condenser coil.
 

Last edited by techgeek6811; 08-01-16 at 09:55 PM.
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Old 08-02-16, 07:57 PM
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Yes it is a no rinse solution.
I use it when a water hose is not an option.
 
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Old 08-03-16, 01:25 PM
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While certainly not perfect, it's much better than it was. I was also able to straighten most of the bent fins with a fin comb. I also purchased the recommended Evap Coil cleaner, both the cleaner and the comb set were available at Ecco. It was a very awkward place to work, but with some perseverance I was able to do a decent job in my opinion. Here is my final result:

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I checked my airflow at the register and it has improved greatly. Unfortunately I will have to wait awhile to find out the difference it's made to my AC performance as I am waiting on a condenser fan. The parts guy told me it's coming from Tennessee and it will be here in two weeks. I'm hoping it's much sooner than that, I think he told me two weeks as a worst case scenario so I wouldn't hassle him daily with "where's my fan".

So right now I'm imagining with all the servicing I've done that there will be little piles of snow accumulating at the registers when I turn it on.
 
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Old 08-05-16, 10:24 PM
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That's a big difference in the coils. Good job. I hope it made a difference in cooling the house.
 
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Old 08-06-16, 09:53 AM
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Thanks, I did my best with the access I had.

As for whether it made a difference, I won't know until my new condenser fan comes in. That's what started this journey actually. The condenser fan was making noise. I had replaced the condenser fan motor a few years back due to a bad bearing. So when it started making noise again, that's what I thought it was. Changed the motor and I still had noise. Then I discovered that the fan was out of balance and it was squeaking caused by the vibration. With the fan on the motor shaft, I could see that it was ever so slightly bent. I tweaked it a bit as a short term solution and ordered a new fan. The tweaking helped reduce the vibration, but unfortunately the fan had other ideas and the crimp on the hub loosened and began to spin freely inside the fan. That was a horrendous noise. So now I'm waiting on the fan. I thought since I had so much time, I'd service the evap coil and I've even combed out the condenser coil. I hope I can get a couple more years out of this AC unit. The fins on the condenser coil are very corroded. The fins seem to have "rotted" towards the bottom because in some places where I combed they literally fell apart if I tried to straighten them.

So when the fan comes in, I'll be sure to update this post. Hopefully this post will help someone else down the road.
 
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Old 08-11-16, 06:25 PM
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Well no piles of snow. I installed the condenser fan and initially it was silent with almost no vibration, but after a couple of hours it's vibrating again. I found only a small amount of pressure over the fan mount eliminates the vibration. I've placed a stone that weights maybe 5lbs and that seems to have done it. Not the most elegant solution, but I think because the frame of the AC unit is quite flimsy, it's unable to dampen the small vibration.

After a couple of hours, it's cooled the house by about 2F. I've measured the air at the register and compared it the the thermometer and there is about a 13 F to 14F difference. I think this should be better. However I think the humidity in the house is affecting overall performance. It's been cooler here because it's been raining nearly every night and some during the day. We've been keeping the windows open to help cool the house, but this has made the house very humid and I think that now that the AC is on, it's going to take awhile to remove the moisture from the air. I'm hoping that the cooling will improve once this has happened.
 
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Old 08-12-16, 05:21 AM
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Yes, the rate of cooling is directly tied to the humidity. The more humidity in the air, the longer it will take for the temperature to drop (most of cooling is going for dehumidification rather than cooling). When the RH drops to ~50% inside, then remeasure the Delta T. Ideally, it should be somewhere in the range of 15-20 degrees F.
 
 

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