How to Clean and Straighten AC Condenser Coils

This project shows how to clean and straighten the outdoor air conditioner condenser coils for better efficiency and cooling.

The AC condenser coils need regular maintenance and cleaning along with the indoor AC evaporator coils because the condenser unit is other half a split central air conditioner system. The purpose of the condenser coil is to release the heat absorbed by the refrigerant at the evaporator coils inside the home so it’s ready for the next cooling cycle. If the condenser coils are clogged with dirt or the fins are bent it will block air flow through the coils and interfere with the heat exchange. This causes the system to work harder and drives up your electric bill.

This video explains how a central air conditioner system works:

Bent AC Condenser Coil Fins

The air conditioner system was installed by the home builder and are now about 12 years old. The Heil “entry model” or economy condenser units have coils that are protected by a wire grille which in reality isn’t much protection. I noticed the condenser coil fins had become bent and damaged sometime in the past 2 years. Were the fins bent by the hail storm or more likely by the pressure washer guy?

The bent condenser coil fins are very noticeable in the 2012 photo. The damaged fins are straightened by fin combing in the 2014 image:

Outdoor AC Condenser Units Before and After Fin Straightening

Outdoor AC Condenser Units Before and After Fin Straightening

How to Clean and Straighten AC Condenser Coils

I called my HVAC service company for the twice a year seasonal maintenance and asked for condenser coil cleaning and fin combing to straighten the bent fins which cost an extra $125 per unit.

These are 3 ton (or 36,000 BTU/hr) condenser units. The coils are painted black by the factory which has mostly worn off. The coils show numerous silver looking areas with bent fins or impact damage. The individual strikes could be something thrown by the lawn mower or a hail strike. That bent fins near ground level are probably from careless use of the weedeater. I believe the pressure washer guy caused the large area of bent fins at the left corner when he cleaned the house (BTW – never pressure wash AC coils!):

Outdoor AC Condenser Bent Fins

Outdoor AC Condenser Bent Fins

The condenser unit wire grille must be removed to comb and straighten the fins. The AC service tech shutoff the electricity at the outdoor service disconnect before starting work, then removed the sheet metal screws to lift off the fan unit and grille. There’s sufficient slack in the fan wiring to lean the top against the wall without disconnecting the wiring:

Outdoor AC Condenser with Top Panel and Fan Removed for Cleaning

Outdoor AC Condenser with Top Panel and Fan Removed for Cleaning

The rain-proof AC electrical service disconnect box on my home has four 30 AMP breakers (two breakers per condenser unit) rated at 220 Volts:

AC Condenser Unit Electrical Service Disconnect

AC Condenser Unit Electrical Service Disconnect

A look inside the outdoor AC condenser unit showing the scroll compressor. The factory black paint is mostly intact inside the coils. Another thing I don’t like about the entry model condenser units is leaves, seeds and other tree debris easily falls through the fan grille (that’s why I bought a Trane XL16i for my former Florida home which has a solid top cover and sheet metal sides to protect the unit). The leaves aren’t a big deal but I asked the AC service tech to scoop the leaves out of the bottom pan which is about half-way done here:

AC Condenser Unit Interior View with Scroll Compressor

AC Condenser Unit Interior View with Scroll Compressor

View of the leaves in the bottom pan of the other AC condenser unit:

AC Condenser Unit Interior View before Leaf Cleanout

AC Condenser Unit Interior View before Leaf Cleanout

It amazes me how people will plant bushes or let vines grow against or over their condenser units. AC units aren’t pretty but need plenty of room to for proper air flow with at least 18 to 24 inches of side clearance and 4 feet above.

Copeland Scroll Compressor

The label on the side of the AC compressor (not visible in the above photo) of says it’s a Copeland Scroll Compressor model ZR36KC-PFV-130. The compressor specifications state:

  • Capacity BTU/HR: 36900
  • SEER BTU/WH: 11.0
    11 SEER is a fairly low energy efficiency rating. New units are rated 18 to 21 SEER. See how much you can save with the Lennox Energy Savings Calculator.
  • Electricity Frequency-Phase-Voltage: 60-1-208/230
  • Refrigerant: HCFC-22 (also known as R-22) which has been discontinued due to environmental concerns and replaced by R-410A. However, R-22 is still available for servicing older system such as mine.

The scroll compressor is an expensive part to replace in a central air conditioning system requiring specialized tools and training. My Copeland ZR36KC compressor has been replaced by the newer ZR38K5 series per the Copeland Scroll ZRK5 Compressor Cross Reference Guide and a new compressor would cost around $600. With installation labor and materials the total repair would be in the $900 or $1000 range. But if something major were to fail I would just replace entire system because it’s old and not very energy efficient.

This video show how a Copeland scroll compressor works:

AC Condenser Coil Cleaner

After combing out the condenser coil which straightened most the fins (more on this shortly), the AC technician reinstalled the wire grille and top cover – see the following photo.

Condenser coil cleaners like Nu-Calgon Nu-Brite are alkaline detergents containing sodium hydroxide (lye) meaning it has a PH value of about 13 which is highly caustic, can burn your skin/eyes and the fumes are harmful. Therefore condenser coil cleaners must not be used to clean indoor evaporator coils. Condenser coil cleaners usually require hosing off with water so it doesn’t deteriorate the aluminum coils.

Nu-Calgon Nu-Bright Condenser Coil Cleaner

Nu-Calgon Nu-Bright Condenser Coil Cleaner

Carefully read the manufacturer’s instructions and the Good Practices & Procedures for Coil Cleaning before using.

Nu-Calgon Nu-Bright Condenser Coil Cleaner Directions for Use

Nu-Calgon Nu-Bright Condenser Coil Cleaner Directions for Use

Because Nu-Bright contains sodium hydroxide which is a paint stripper, the product label (see above) states:

“For painted fins or microchannel coils… consider Tri-Pow’r HD, Cal-Green, CalClean or TriClean 2x”

because those other products don’t contain sodium hydroxide and are gentler on the coil fin paint. Your condenser coils may be painted black or have a silver color powder coat for corrosion protection so check your manufacturer’s specifications. For microchannel coils I believe the concern is it’s more challenging to thoroughly rinse the cleaner out of the very small zig-zag fin design.

AC Condenser Coil Cleaning Steps

Shutoff the electricity for the air conditioning system at the outdoor electrical service disconnect or at the house circuit breaker panel. Don’t trust the thermostat because someone may turn it On while you’re working outside. The reason for shutting off the electricity is to prevent the condenser fan from inadvertently running and slinging the caustic chemical cleaner into the air and onto you!

Cleaning the coils was easy:

  1. Pull the water hose over to the condenser units.
  2. Mix the coil cleaner in the pump sprayer per the manufacturer’s instructions.
    Fill the sprayer with water first followed by the cleaner.
  3. Spray on the coil cleaner.
  4. Wait about 5 minutes for the cleaner to foam up.
  5. Wash off the cleaner and dirt with the water hose.
Cleaning AC Condenser Coils with Pump Sprayer

Cleaning AC Condenser Coils with Pump Sprayer

Hosing off the coil cleaner. This photo doesn’t do justice for how much dirt and debris was washing off the coils:

Outdoor AC Condenser Coil Cleaning - Hose Off the Detergent

Outdoor AC Condenser Coil Cleaning – Hose Off the Detergent

Remember to turn the electricity back On when finished.

How to Straighten Air Conditioner Coil Fins

A fin tool with various size interchangeable heads is used to comb and straighten the evaporator or condenser coil fins. Fin tools are inexpensive so I bought two sets with 8 to 14 and 13 to 20 Fins Per Inch (FPI) because I wasn’t certain which would fit my AC system. As it turned out the black color 12 FPI head fit my condenser coils.

AC Fin Tools with Interchangeable Heads

AC Fin Tools with Interchangeable Heads

The Fins Per Inch are marked on each head. Take care to use the head that matches your coil fins:

AC Fin Tool Closeup

AC Fin Tool Closeup

I also like the Robinair 18403 fin comb because it has a comfortable handle and 12 different heads on two wheels with easy to read fin sizes:

Robinair 18403 Fin Comb

Robinair 18403 Fin Comb

The AC tech said he doesn’t get a lot customer requests for fin straightening and didn’t have his fin tool on the truck. I said “No problem! I have a set.”

The AC technician shutoff the electricity at the electrical service disconnect before removing the fan cover and wire grille. The condenser coil fins are badly bent on this unit blocking the air flow. The tech estimated 25% of the air flow was blocked. I think the pressure washer guy was careless when he cleaned the walls.

Outdoor AC Condenser Coils - Bent Fins

Outdoor AC Condenser Coils – Bent Fins

The AC tech combed the fins by starting at the bottom and pulling the fin tool upward in one steady motion. Why comb from bottom to top? Because combing downward would cause the fin tool handle to touch the ground and stop short. The fins to the right of tech’s hand have been combed and straightened. Recall the dark areas are where the factory black paint coat has worn off.

Outdoor AC Condenser Coils Fin Combing to Straighten

Outdoor AC Condenser Coils Fin Combing to Straighten

The fin straightening is working really well. Compare the combed fins to the bent section:

Outdoor AC Condenser Coils - Fin Straightening

Outdoor AC Condenser Coils – Fin Straightening

Nearly all of the bent fins on this side of the condenser coil are straightened which should greatly improve the air flow. Only a few damaged spots near the bottom wouldn’t comb out:

Outdoor AC Condenser Coils After Fin Straightening

Outdoor AC Condenser Coils After Fin Straightening

My total bill for the Spring maintenance service was $931.00 which included:

  • Routine health check for two 3 ton AC systems: electronics, refrigerant charge, furnace, blower motor, filter change, drain pan tablets to prevent algae, clean the condensate line and pump, etc.
  • The AC tech discovered my whole house humidifier on the air handler was wired incorrectly to run when the AC or furnace were On. He changed the humidistat circuit so it operated only when the furnace was running. I turn Off the humidistat in Spring so it’s not fighting the AC, but it’s nice to know it’s wired correctly now.
  • Replace two air handler blower motor capacitors and one compressor start capacitor.
    The capacitors were at 80% so I elected to have them replaced now versus when it’s 100 °F in July.
  • Clean and straighten coils on two condenser units at $125 each.
  • Replace a bad safety cutoff float switch on the axillary (or emergency) drain pan under the attic air handler.
    The new AguaGuard AG-1200+ float switch is way improved over the original lever type switch.
  • $265 annual maintenance plan for two systems (which covers today’s routine work). My Fall system maintenance is covered when it’s time to run the furnace.

Hope this helps,

Bob Jackson

Copyright © 2017   Reproduction strictly prohibited.

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10 Responses to How to Clean and Straighten AC Condenser Coils

  1. Russ R June 12, 2014 at 5:19 pm #

    Thank you for sharing all these details. I am attempting to do a complete go through of my AC unit (Including replacing all the flex duct in a 2 story house) on a unit that works, but was sorely neglected by the previous home owner.
    Fortunately i was able to persude my local hvac supply house to sell me parts and supplies HD and lowes don’t carry. Including the cleaning supplies.
    Not done yet but I know the performance is going to be amazing with inside and outside evap coils clean, no duct leaks and upstairs and downstairs dampers added.
    All totalled I’ve spent about $450 and a fair amount of sweat, but I’ve been detailed and rigorous with the small details and will appreciate every second my family and I spend in a comfortable climate.

    Thank you again for sharing all the details you did. It is only because of you and others like you that I am able to do this by myself.

    • Bob Jackson June 12, 2014 at 7:45 pm #

      You’re most welcome!

      Yes – many HVAC supply stores will do Counter Sales to the general public for those the specialty HVAC items. That’s how I purchased the sheet metal duct and supplies for this job.
      Thanks for writing,

  2. Leslie Jester July 18, 2014 at 11:36 pm #

    Would the Nu Calgon evaporator cleaning solution be an effective cleaning agent to use to clean the condenser ?

    • Bob Jackson July 19, 2014 at 8:49 am #

      Indoor evaporator coil cleaner can safely be used on the outdoor condenser coils, especially if the coils are not too dirty.

      The difference is outdoor condenser coil cleaners are stronger solutions which produce harmful vapors and must be rinsed off with a water hose.

  3. Travis LaFlamme July 21, 2014 at 4:30 pm #

    I cleaned my condenser coil today using this product, and it worked terrific. My coil was extremely dirty and clogged. I have a 2 ton Goodman gas package unit, and my only concern now that I have done this maintenance is did I rinse it off thoroughly enough. I mean, how much should you rinse the coil back down?

    I rinsed it a completely as I possibly could, but still can’t help but be concerned it wasn’t enough. Now that I have cleaned the coil, i have started the unit back and it hasn’t seemed to help. I did have the unit’s pressures check and they were fine. The tech said one thing that I was not sure about, which was that the were non-condensables in the system. I question this due to the cooling side of the system never has been opened.

    Anyway, any help you could suggest would be great!



    • Bob Jackson July 21, 2014 at 8:30 pm #

      Hi Travis,
      That’s great!

      Which condenser coil cleaner did you use? Nu-Calgon Nu-Bright or the Nu-Calgon CalClean? I featured Nu-Bright in the article and bought a gallon for myself.

      > my only concern now that I have done this maintenance is did I rinse it
      > off thoroughly enough. I mean, how much should you rinse the coil back down?
      Hose it down thoroughly – until the dirt, foam and suds are gone. You should be done in 5 minutes or so.

      > The tech said one thing that I was not sure about, which was that the were non-condensables in the system.
      The air conditioner refrigerant changes from a gas in the indoor evaporator coils to a liquid state in the outdoor condenser coils. This occurs under precisely engineered conditions. If air enters the system it becomes a “non-condensable” because it will remain in a gaseous state throughout the compressor/condenser coil cycle. This degrades your air conditioners performance. The air remains in a gaseous state because it’s physical properties are very different from the refrigerant (R-22 or R-410A).

      Checking For Noncondensables by Air Conditioning, Heating, Refrigeration News explains the problem in detail.

      Also see Purging Air From Refrigeration Systems for “How Air Gets Inside” and what can be done.

      > I question this due to the cooling side of the system never has been opened.
      You’re referring to the indoor evaporator coils inside the air handler? That’s a different issue unrelated to air contamination (non-condensables) inside the refrigerant lines. Dirty evaporator coils can reduce air flow, cooling efficiency and even ice over.

      To check and clean your indoor evaporator coils see these guides:
      * How to Clean AC Evaporator Coils
      * Heavy Duty AC Evaporator Coil Cleaning
      * And the ultimate: How to Clean Inside of AC Evaporator Coils


  4. Jess March 11, 2015 at 8:42 pm #

    Could I spray paint my AC condenser it is still working ,



  5. Larry Zimmerman September 30, 2016 at 7:08 pm #

    My aluminum fins are badly oxidized. Will the Nu-Brite clean off the oxidation?

    • Bob Jackson October 1, 2016 at 9:15 am #

      The condenser coils have a white powdery film of aluminum oxide? Nu-Brite is alkaline and should remove some of the buildup.

      Aluminum reacts with oxygen in the air to form a very thin protective layer of aluminum oxide. The coil manufacturers apply various coatings (paints, polymers) at the factory to further protect the coils because the natural aluminum oxide layer can be attacked by salt, acid rain, etc.

      When aluminum oxide has a powdery appearance it means corrosion is eating through causing the oxide layers to reform and become chalky.

      Regular coil cleanings will reduce corrosion. The coils must be thoroughly rinsed to remove all cleaning solution residue so it doesn’t contribute to the corrosion.

      After-market coil coatings are available. Ask your HVAC service company or try Nu-Calgon Cal-Shield:

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