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I was going through my blog roll this morning when I saw that someone had asked this elsewhere. I figured it would be a good question to ask.

In general, how long do evaporator coils last in a home AC system? How can I make them last longer? If I want to replace them, what should I keep in mind?

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Keep corrosive agents away from them, don't decide to defrost them with an ice pick. And you don't replace them, you replace the unit. The compressor will probably be the item that quits. – Fiasco Labs Dec 27 '13 at 2:43
up vote 5 down vote accepted

They should last for the life of the A/C system, which is generally 15-20 years for a high quality system. (Many people end up replacing their systems between 12 and 15 years due to efficiency issues or deferred maintenance causing damage to more easily damaged components, such as the compressor.)

Most of the time, evaporator coils fail because they are allowed to get dirty or are allowed to have ice build up on them. Things you can do yourself to help prolong the life is to make sure you change your HVAC intake filter regularly and use a high quality filter (filters should be in place for no more than a month, and should be replaced sooner in a dusty environment if you can no longer see light through the filter), and make sure that your evaporator coils are draining correctly.

The easiest way to make them last longer is to have a licensed HVAC technician perform regular maintenance on your system. This should be done once a year, typically in the winter time. The technician will clean the coils and check them over. At the same time, the A/C tech will check to make sure that your coolant is at the right level/pressure and that there are no leaks in your system.

If you replace them, you probably want to replace the entire system at this point thanks to many recent gains made in efficiency.

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Once a MONTH for filters??? Do you have an industry source for that? – HerrBag May 31 '13 at 22:07

Coil Life
I'm not sure if how long they "should last" matches most home owners experiences. Looking at many consumer complaint websites showed many users with failure between 5 and 7 years.

Recommended Maintenance Didn't Save Me
You should always do the recommended maintenance, but in my case maintenance wasn't the problem. I have a 14.5 SEER, 2.5 Ton Carrier unit. The evaporator coil started leaking after 43 months (under 4 years). It was a small leak where the copper met the rusty metal housing. I used high quality filters and replaced them every 2-3 months. They never looked dirty but I still replaced them within the recommended window. It was under a service contract and had preventative maintenance done by a licensed tech from AC-Designs in Central FL every 6 months (twice a year).

The parts were under warranty but labor was not so it was a little over $600 to replace with a 90 day labor and 1 year parts warranty. The tech did note that my case was unusual and he's seen both extremes with some lasting the life of the system (15+ years).

One thing he mentioned on replacement is some replacements are aluminum based evaporator coils vs the copper in hopes of a longer life. I don't know which is better but I found this article about copper vs aluminum here.

Depending on the system, sometimes it makes more since to replace the whole system. Get quotes on each (preferably by 2 or more vendors) before you decide.

The department of energy has some other great info on AC systems here.

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