Is your air conditioner making your room feel more like a subzero icebox? Are your energy bills going through the roof? You never know, your AC evaporator coils might just be the unsung (or sung) heroes of your comfort. Let’s get into it.

Your AC evaporator coil is a pivotal aspect of your overall HVAC system, actively playing a critical role in the cooling mechanism of your home air conditioning or heat pump system. This bad boy is usually tucked indoors drying off, hanging out in or immediately next to your air handler or furnace. It is the place where your system inhales warm indoor air and exhales a crisp, cool breeze.

Understanding AC Evaporator Coils: A Comprehensive Guide

But just what is an evaporator coil and why do you give a damn?

Consider the evaporator coil as the great heat sponge for your house. It’s that all-important bit where the magic happens: Refrigerant takes the heat from your indoor air, transforming balmy mess into cool comfort. You may occasionally hear it referred to as an “evaporator core,” or even an “A” coil, because of its common triangular shape.

Where does it hang out? That coil is always inside your house, usually tucked away in your air handler or furnace. If you have a downflow system, it’s actually going to be underneath the furnace. Constructed from sturdy, heat-loving materials like aluminum or copper, these coils are designed to take heat transfer and knock it out of the park. They’re typically U-shaped tubes covered in thin metal fins to grab every little bit of heat from the air.

How AC Evaporator Coils Work

Here’s the play-by-play on how those coils get to work to keep you cool:

• How Refrigerant Flows and Absorbs Heat: Okay, first off there is the cold” refrigerant (a low pressure liquid) that arrives at the evaporator coil. This occurs after it passes through a metering device, such as an expansion valve, which reduces the pressure of the refrigerant and quickly cools it. In the meantime, your HVAC system’s blower fan is working hard to draw warm indoor air over this super-cold coil. “Thank you for the heat!” the refrigerant inside says, as that air runs past. and sucks it all up, vaporizing into a gas and abruptly cooling the air around it.
• Dehumidification: Curious how your AC cools the air so that it does not feel as sticky? This is it. When that warm, indoor air loaded up with water vapour makes contact with the ice cold AC evaporator coils, the water vapour in the air says, “I’m outta here,” and it becomes liquid. This pooled water then drains down neatly into a condensate pan below it, and is drained away, effectively removing humidity from your home. It’s a twoforone special: cool, dry air.
• Cool Air Circulation: With the heat removed and the evaporated air out, the cool air is circulated back into your room, lowering the temperature as it is blown out.
• Return To Refrigerant Cycle: The refrigerant, which was now a gas filled with heat, isn’t going to hang around. It carries that thermal load onto the outdoor condenser unit and dumps all that heat that it absorbed into the great outdoors. When it’s released all that heat, it cools off, and in the process turns back into a liquid and runs through coil (back to the evaporator coil to start the whole dance over again). It’s a closed loop — it’s always draining heat away from your home.

Types of Evaporator Coils

They’re not all created equal when it comes to AC evaporator coils. You’ll usually encounter two primary varieties, and they can be cased or uncased.

• A-Coil: The A-shaped metal component (you read that right—named after the shape of the letter A) will have to do if you have an upright furnace. They are angled just so inside of your air handler to ensure that air contacts each side for optimal heat transfer and efficiency. You can get ’em cased, or uncased.
• Slab Coils: These are coils shaped like slabs, or flat and rectangular in shape, used in horizontal configurations where space is at a premium such as attic or crawlspaces. For compact, efficient cooling, they make cases for them, too.

And then there is the housing decision:

• Cased Coils: The comes all wrapped up, cased in a metal case ready for installation. The housing makes this install a bit easier and gives the coil some physical protection against accidental bumping/thumping or environmental damage.
• Un-Housed Coils: These coils are not housed. They are frequently selected for bespoke installations that require a precise fit.

Why You Should Clean Your AC Evaporator Coils

Listen, Caring for your AC evaporator coils isn’t just advisable, it’s also necessary for the health of your HVAC system as well as your pocketbook. Dirt, dust and other kinds of crud inevitably accumulate on the coil’s surface over time. This buildup works like an insulating blanket that finally prevents the coil from performing its only task, which is to absorb heat.

Here’s what happens as a result of dirty coils – and the results aren’t pretty:

• Poor Cooling Performance: When that coil is covered with gunk, it’s not efficient at absorbing heat. This in turn forces your AC to work harder, but provide less cool air and reduce its functionality by 30 percent or more. It’s as though you’re running a marathon with a weighted vest — you’re using more energy for less distance.
• Increased Energy Usage: A sluggish system requires your AC to operate for extended periods of time and at maximum output to meet your target comfort level. And guess how that extra effort is paid for? You do. We’re discussing energy bills 30 to 40% higher. That’s real money, as in not Monopoly money.
• Frozen Coils: That’s another big one. If the coil cannot absorb enough heat, the refrigerant stays too cold. What happens then? The coil is frosted over rather than the water vapor condensing and draining. You are left with a bundle of coil that is a frozen doughnut. When that coil gets too cold, it gets ice on it, and the ice means your system has to shut down. And, left to its own devices, it can even cause your compressor to go to the big air conditioner in the sky. Not ideal.
• Reduced Equipment Longevity: All that added work for the dirty coil ages your entire HVAC unit faster. It’s further akin to driving your car on fumes — eventually parts will begin to break down, cutting your system’s lifespan short.
• Greater Pressures and Temperatures: Running with a dirty coil causes the system to work under higher internal pressures and temperatures and that’s a surefire way to wear out your system too soon.
• Bad Quality Indoor Air: Those same can dirty coils harbour mould and bacteria due to the wetness caused by condensation, leading to bad quality air inside your home. No one wants to be breathing that.

Common Problems and How to Detect a “Bad” Evaporator Coil

The AC evaporator coil is tough, but it’s not indestructible. Here are the usual suspects for when things go wrong, and how to identify them:

Dust Build Up: T his is the most common of all of them. It occurs when your air filter is dirty or, much worse yet, not present at all, allowing that desirable dust and dirt to deposit on your coil. Well, it’s actually dust, and it serves as an insulator, preventing the coils from doing their job of cooling. Replace your air filter often – every 1-3 months, to be exact, depending on the use and type. It’s a cheap preventative measure.

Frosting Over/Prefreezing Coils: So what we see here is that if the coil is unable to soak up heat because of the grime, the refrigerant is going to be too cold and water vapour is going to freeze when it comes in contact with the coil. You may be able to see ice on the coil. When There is a Low Level of Refrigerant This can also happen because of the low level of refrigerant. When you spot the ice, you have a problem.

Refrigerant Leaks: These are sneaky. They can appear due to moist air and normal household chemicals (Volatile Organic Compounds or VOCs from new carpets, cleaners, air fresheners, etc.) wearing down the coil over time. Look for oily residue on the evaporator coil or in the drain pan. If your system suddenly doesn’t have as much refrigerant as it did a week ago, you have a leak.

Signs of a Faulty Coil: Your unit will give you signs. Don’t ignore them:

• System not turning on.
• Hot air from your vents.
• The AC cycling on and off without bringing down the temperature in your home.
• Weird sounds — a hiss, a bang.
• Obvious oil residue that indicates a freon leak.

If you spot any of these, the time is ripe to bring in a pro to investigate. Refrigerant is nothing to play with — it’s toxic, so keep kids and pets away if you suspect a leak.

Cleaning Your AC Coils: How to Clean AC Evaporator & Condenser Coils (DIY vs. Pro)

OK, brave soul, want to take this on yourself? Cleaning your AC evaporator coils can save you some money – professional cleaning costs for AC coil could range anywhere from £500 to £1,000 or sometimes even more, depending on if they have to take the coil out. But as always, a word of caution: safety first.

Safety First: Once you have your hands on it, the absolute first thing you’ll want to do is turn the air conditioner off at the thermostat, and then flip the circuit breaker switch that controls the power to your AC unit to the off position. Your coil is connected to high-voltage power, and you don’t want to join the circuit. After you cut the power, verify it by trying to power on the system – it should not boot.

If you’re daring, here’s the DIY playbook:

1. Accessing the Coils: Locate your indoor air handler. You will have an access panel to pop out, typically via unscrewing or releasing clips. You may need to remove exhaust venting or other covers, depending on your setup. But I had a serious wrestle with covers and a float switch to get to the coil, for example. Some of the time you can just take off the whole coil assembly; sometimes you’re working in Crawler space.
2. Initial Debris Removal: Idegal that dry, as well, removing debris. Get out a shop vac or a coil comb. Use a vacuum, or just comb it out, to get big dry crud like leaves, bits of bark or grime out of the fins. Be ever so careful here – those fins are quite fragile and can very easily be bent out of shape. A crooked fin is less airflow and less efficiency. My coils were also fairly disgusting after just 3.5 years because air was bypassing the filter – this initial dry clean extracted a shocking amount of gunk.
3. Applying Coil Cleaner: Now that the big debris is out of the way, it’s time to foam the house. For HVAC coils, use a foaming coil cleaner. Shake the can thoroughly, then spray it on the coils, moving from bottom to top for optimal coverage. Let it sit for 10-15 minutes. Some are “no-rinse” — they use the air conditioner’s own condensation to do the rinsing.
4. Rinse the Coil: If your cleaner isn’t a no-rinse product, or if you’re just a stickler for cleanliness, rinse the coil thoroughly. Use a garden hose with low pressure, such as a fan or shower spray. Spray from the inside out, directing debris away from the machine. I’ve had some nasty, dark water drain out of coils after doing this — satisfying, but also goes to show how much grime was in there.
5. Clean the Condensate Drain: While you’re in the crawlspace, inspect the condensate drain line. And dirt, algae or mold can cause this line to become clogged. Suck out any clogs with a wet/dry vacuum or pour a bleach and water solution into it to kill biological growth. That is, if a drain is clogged, water can back up and spill over in your home.
6. Replace Air Filter – This is also a MUST, no questions asked. Dirty Coils Dirty coils are the result of a dirty air filter. Change your filter every 1-3 months for optimal performance or three (3) to four (4) times per year. Confirm your filter has a good seal and that air isn’t sneaking through beside it.
7. Reassembly and Test: Gently reassemble all access panels. Watch for wires or fan blades. Restore power to the unit. Switch the air conditioner on and ensure the airflow is strong and that the air coming out of the vents is cool.
8. How often should you clean AC coils? Clean your AC coils every 12 months. If you reside in a dusty area, or if your AC seems to always be running, you may have to perform it more regularly.
9. When to Call a Professional: If the idea of slinking all over the floor to find and clean your coil makes you break out in a cold sweat or you can’t readily access your coil, don’t. If you have reason to believe you have a refrigerant leak or if the coil is heavily frozen or appears damaged, call a licensed HVAC professional. They have the proper tools and the knowledge to navigate tricky situations, and even to pull the coil, should that be necessary.

Benefits of High-Quality Evaporator Coils

Selecting a premium AC evaporator coil is not just about looking good, though it is always wise to be mindful of aesthetics in most every facet of life.

• Energy Efficiency: Improved product construction and better materials result in superior heat transfer. This translates directly into more energy efficient cooling and, obviously, lower utility bills.
• Better Comfort: The compressor also time-released the temperature and humidity, so it offers you a better comfort. That’s even comfort, no hot spots.
• Long-Lasting: Today’s coils are usually constructed with long lasting materials such as copper or aluminum. This’s not futuristic however definitely harder towards moisture and airborne chemicals, providing you a long standing dependable performance.

Evaporator Coil Replacement

Sometimes, cleaning isn’t enough. Additionally to all that has been mentioned, if you have a leaking refrigerant or continuously frozen evaporator coil, despite cleaning it, a replacement might be in the cards.

• Cost: This isn’t pocket change. Evaporator coil replacement costs vary from £550 to £2,500. How much it will cost you The cost for replacing the coil depends on such factors as whether your unit is under warranty and the size of your coil. Your heating and cooling pro can steer you in the right direction in terms of repairs versus a complete system replacement.

Evaporator Coils vs. Condenser Coils

These two coils are like the dynamic duo of your AC system – they work together but do different jobs.

Condenser Coil Maintenance

Your outdoor condenser coil is just like your indoor condenser coil; it needs your love, too. Strong airflow is a necessity for both coils.

• Debris Check: Inspect your outdoor condenser unit for accumulation of outdoor debris such as grass clippings, leaves, twigs, and pet hair. There’s all this things that can clog the fins, and makes it more difficult for the condenser to get rid of its heat.
• Cleaning Closed Item: Make sure to turn off power to the outdoor unit first. Do a “candy wash” on the fins, and carefully brush away the dirt. While you may see neighbors tiptoeing out to smother their outdoor unit for winter, it’s not typically a great idea; it can trap moisture and expose the thing to rust. Snow can be kept out by a piece of wood on top, hemmed in by bricks.

When your AC can’t seem to carry its weight, or your utility bills are riding high, think about your AC evaporator coils. Keep them clean and keep them healthy, and they’ll keep you cool without costing you an arm and a leg.