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Is Rust on Your Evaporator Coil a Major Problem for Your HVAC System in Southwest, Florida?

Danny Ramos

Updated: Jan 31

Living in Naples, Florida, where high humidity and hot temperatures are the norm, your HVAC system plays a vital role in maintaining indoor comfort. Often times air conditioning technicians note rust as a sign for concern but is rust a sign of a serious issue, or is it something you can overlook? Let’s break it down.


What Causes Rust on an Evaporator Coil?


Rust on evaporator coils is primarily confined to the metal parts that support the coil. These supporting structures are typically made of steel, which is prone to oxidation when exposed to moisture. Given that evaporator coils are designed to collect water from the air, some rust over time is normal. However, this rust doesn’t mean the coil itself is deteriorating.
The coil’s refrigerant lines are usually made of copper or aluminum, which don’t rust. However, formaldehyde and acetate for example, found in small quantities in household items like plywood, cosmetics, deodorizers, and carpet adhesives, are major contributors to evaporator coil corrosion. On their own, these substances are not harmful, but when combined with moisture on the coil, they form organic acids that weaken the thin copper or aluminum tubing. This corrosion leads to faint etchings on the coil, which can eventually develop into leaks, causing refrigerant loss and system inefficiency.

Rusty evaporator coil

When Should You Worry About Rust?


While some rust is natural, excessive rust on a relatively new coil could indicate a problem. Here are a few scenarios to consider:
  • Normal Aging: Over time, rust can develop on the supporting metal parts without impacting the performance of your HVAC system. Excessive rust on the supporting metal parts can diminish the structural integrity of the evaporator coil and lead to possible leaks
  • Signs of Corrosion: Corrosion from contaminants, not rust, is the primary cause of leaks in evaporator coils. If you notice performance issues, such as reduced cooling efficiency or increased energy bills, corrosion might be the culprit.

How to Confirm a Leak


If a technician claims your coil is leaking due to rust, ask for definitive proof. Reliable methods include:
  • Soap Bubble Test: A simple but effective way to identify leaks.
  • Electronic Leak Detection Test: A more advanced approach for pinpointing refrigerant loss.
  • UV dye test: A UV dye check is a method of detecting refrigerant leaks in a home's AC system by adding a fluorescent dye to the refrigerant. When the system is inspected under UV light, any leaks become visible as glowing traces of the dye, making it easier to locate even small or hard-to-find leaks.
Without these tests, it’s hard to definitively link rust to a refrigerant leak.

The Impact of Evaporator Coil Leaks


A leaking evaporator coil can have significant consequences, including:
  • Decreased Cooling Efficiency: Lower refrigerant levels make it harder for your system to cool your home.
  • Higher Energy Bills: Your system will run longer to compensate, driving up energy consumption.
  • Increased Wear and Tear: Prolonged operation with inadequate refrigerant can strain other components, leading to expensive repairs.

Preventing Problems with Your Evaporator Coil


To protect your system, consider the following steps:
  1. Regular Maintenance: Schedule seasonal check-ups with a trusted HVAC contractor to spot early signs of rust or corrosion.
  2. Change Filters Frequently: Clean filters reduce contaminants that can cause coil corrosion.

Conclusion


Rust on your evaporator coil’s support structures is not inherently a major problem, especially in Southwest Florida's' humid climate, where some rust is expected. However, excessive rust on a young coil or signs of refrigerant leaks warrant closer inspection. Regular maintenance and prompt attention to potential issues will help ensure your HVAC system runs efficiently for years to come. If you’re concerned about rust or suspect a leak, consult a reliable HVAC professional for an accurate diagnosis.

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