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Old 07-17-2010, 09:41 PM   #1
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How to clean evaporator coil on central A/C when it sits on top of furnance


Hi,

I have a Carrier central A/C and heating system. The condenser is outside, the furnace is in the garage, and the evaporator sits on top of the furnace. The model number of the evaporator is 28rc024000 and is a Carrier unit. It was installed in 1989....some 22 years ago.

The last person who lived in this unit never had a air filter installed and ran the unit 24/7. Although the unit still works, the air flow is really poor. (I know this because my neighbor has the exact same unit and it blows twice as strong.) I've read stuff on the internet and I'm guessing my evaporator is probably clogged.

My question is....Does anybody know if I can even take apart the evaporator so I can get to the coils? Also, I know most people clean the evaporator coils with high pressure water. Can I clean this evaporator if it sits on top of the furnace?

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Old 07-17-2010, 11:25 PM   #2
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How to clean evaporator coil on central A/C when it sits on top of furnance


Doesn't need to be high pressure.

Coil may need to be pulled out from its case to clean. Depends on the install set up.

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Old 07-18-2010, 03:28 AM   #3
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How to clean evaporator coil on central A/C when it sits on top of furnance


pull cover off coil and you will see the evap. There are screws that hold on a prymid shaped metal panel; remove screws and carefully remove panel.

You are know looking at the underside of evaporator coil. There is probably so much birt build up it is matted. Brush big pieces off with a stiff fiber brush and use shop vac to catch debris.

I would than get a good quality coil cleaner from HVAC dealer (the kind that rineses from the condensate as ac operates or a regular garden hose taing care not saturate furnace components).

Saturate coil and rinse as outlined.
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Old 07-18-2010, 04:20 AM   #4
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How to clean evaporator coil on central A/C when it sits on top of furnance


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Originally Posted by hvaclover View Post
pull cover off coil and you will see the evap. There are screws that hold on a prymid shaped metal panel; remove screws and carefully remove panel.

You are know looking at the underside of evaporator coil. There is probably so much birt build up it is matted. Brush big pieces off with a stiff fiber brush and use shop vac to catch debris.

I would than get a good quality coil cleaner from HVAC dealer (the kind that rineses from the condensate as ac operates or a regular garden hose taing care not saturate furnace components).

Saturate coil and rinse as outlined.
Here's a picture of a carrier evaporator (this is not my model.)



According to this picture, the triangle metal piece does not seem removable. Any suggestions?
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Old 07-18-2010, 06:46 AM   #5
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How to clean evaporator coil on central A/C when it sits on top of furnance


The end plate is removable. But not an easy thing to do. May need to pull it out of the case, and clean it from the bottom up.
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Old 07-19-2010, 02:50 PM   #6
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How to clean evaporator coil on central A/C when it sits on top of furnance


I finally got to work on my A/C today. I removed the triangle metal piece which was held by three screws. I actually had to cut the piece before i removed it. I didn't want the metal piece to damage the copper tubing. The inside of the coils was so dirty there was actually a layer of dust as thick as 2 quarters. The layer of dust came out in a few big piece, sort of like the lint trap in a dryer. I also sprayed some coil cleaner I purchased at a A/C store. I don't know if this coil cleaner actually works. It foams up like the shower wall cleaner. I figure that since I already took it apart, i had clean it the best possible.

The A/C is blowing out at least twice as strong now. It took me about 2 hours to clean do the job. Next time I think I can do it in less then 30 minutes.

THANKS FOR YOUR HELP!!!!!!!!!!!!

ps. I can't wait until the electricity bill comes. I'm hoping it will be a lot cheaper after the cleaning.

Last edited by stanlam; 07-19-2010 at 04:08 PM.
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Old 07-19-2010, 04:06 PM   #7
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How to clean evaporator coil on central A/C when it sits on top of furnance


They get like that. That plate is no fun to remove. Glad you got it cleaned.
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Old 07-20-2010, 11:38 PM   #8
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How to clean evaporator coil on central A/C when it sits on top of furnance


Hey thanks for the helpful post. I used this info to clean my evaporator and there is definitely a noticeable difference.

To get the cover off of the evaporator box I had to cut it, because the copper lines were soldered into place after the cover went on. I cut off 2 small pieces and kept them. When I reinstalled the cover I put extra screws at the edge of the panel where I cut the pieces off, and aluminum taped the seams.

I didn't want to cut the triangle panel inside, because I wasn't confident about how it would hold up in a damp enviornment if I taped it back together. I was able to slide it off to the side enough so that I could get my hand in side and comb a lot of the lint off. Then I sprayed some foaming cleaner in there, hopefully it got off what I couldn't get with the comb.

Also, before I started the unit I took the cover off the bottom, and used a shop vac and to clean out the inlet duct. I also used some compressed air to blow out the fan. I had the shop vac running while I was blowing and got it to capture a lot of the dust that flew everywhere.
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Old 07-20-2010, 11:44 PM   #9
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How to clean evaporator coil on central A/C when it sits on top of furnance


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Originally Posted by teg916 View Post
Hey thanks for the helpful post. I used this info to clean my evaporator and there is definitely a noticeable difference.

To get the cover off of the evaporator box I had to cut it, because the copper lines were soldered into place after the cover went on. I cut off 2 small pieces and kept them. When I reinstalled the cover I put extra screws at the edge of the panel where I cut the pieces off, and aluminum taped the seams.

I didn't want to cut the triangle panel inside, because I wasn't confident about how it would hold up in a damp enviornment if I taped it back together. I was able to slide it off to the side enough so that I could get my hand in side and comb a lot of the lint off. Then I sprayed some foaming cleaner in there, hopefully it got off what I couldn't get with the comb.

Also, before I started the unit I took the cover off the bottom, and used a shop vac and to clean out the inlet duct. I also used some compressed air to blow out the fan. I had the shop vac running while I was blowing and got it to capture a lot of the dust that flew everywhere.
I thought I did a good jobs. Your job is awesome. I'm glad you posted all those pictures. I'm sure your pictures will be used by a lot of other people who will use it as a reference when they clean their evaporator coils.
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Old 07-21-2010, 02:00 AM   #10
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How to clean evaporator coil on central A/C when it sits on top of furnance


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I thought I did a good jobs. Your job is awesome. I'm glad you posted all those pictures. I'm sure your pictures will be used by a lot of other people who will use it as a reference when they clean their evaporator coils.


This is probably one of the most important thread a DIY can read. Dirty coils cause low suction press since no heat can be absorbed thru the dirt.

This will often lead to a poor tech assuming low charge on a job and add unneeded refrigerant.

Had one the other day. Guy came out before charged 1 lb ofR22. Low side press read 80psig on a 85* day with 98% RH.

Condenser was pumping luke warm air when it should have been hot.

A coil cleaning and some slight supply alteration and the new press was 72psig with ODT 85* and 50% RH. The clean coil with improved air flow was rejecting 35* over ambiant where before it was barely 20*.

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