Heat pumps are unique pieces of HVAC equipment because they offer both heating and cooling power from a single device. However, the design of the heat pump's condenser coil could leave it susceptible to multiple forms of corrosion. Find out why condensing coils corrode, the risks of a corroding coil, and how to prevent corrosion inside your heat pump.
Causes of Corrosion
All modern heat pumps feature copper condenser coils because copper is less susceptible to rust, which forms due to the moisture present on the exterior. However, copper can still corrode in other ways. The most common causes of copper coil corrosion include:
- exposure to a wide range of chemicals include chlorine and fluoride, which can be deposited on the coil if cleaning products evaporate into the air system
- contamination with formic and acetic acids, which are found in common household products like vinegar, drywall, and paint
- salt, which is a major issue in coastal communities
- water, if it becomes trapped against the surface instead of evaporating and there's another form of corrosion already in progress.
You may not realize you're spraying so many chemicals in your home, but cleaning product residue can easily end up in the air system. If your home was built or remodeled between 2004 and 2007, it could be contaminated drywall fumes that are corroding your condenser coils and threatening your family's health.
Risks of Corrosion
Even if your heat pump's coil looks intact and just has a few patches of corrosion, there's a good chance that it is already leaking refrigerant or will start leaking soon. Due to the way corrosion forms on copper, tiny holes or pits are made from the surface to the interior of the coil. This allows the pressurized gas inside to leak out, reducing the heat pump's heating and cooling abilities at the same time. Unlike with a leaky air conditioner, you'll also lose your ability to keep your home warm if you let a corroding coil go without repairs. Even if the corrosion is on the mounting brackets that support the coil, the damage will eventually spread unless you have it professionally repaired.
Signs of Corrosion
Not sure if your coil is corroded or not? It can be tricky to spot the earliest signs of damage because copper corrosion is not as obvious as rust on steel or iron. Look for the more subtle signs like:
- patches of black discoloration on an otherwise shiny and reddish surface
- unusual splotches of blue and gray
- tiny pits or dots on the surface.
It can be very hard to see the signs of damage until it's too late. Ask the technician who services your heat pump to test the coil regularly by pouring water over the length of the coil while the unit is running. The water test reveals even the smallest leaks because the escaping refrigerant will create cascades of bubbles. Don't try to do this test yourself since pouring the water the wrong way could send moisture into the electrical components of the heat pump.
Treatments for Corrosion
If you manage to catch the warning signs of corrosion before there are any holes all the way through the coil, the metal can be coated with an anti-corrosion spray. This spray will prevent acids and other chemicals from settling on the copper surface and eating away at it. Keeping the coil clean with annual maintenance visits also helps reduce the damaging effects of corrosion by removing build-up before it has time to put the metal. Even after you have the coil coated, you should have it cleaned routinely to preserve the coating itself.
To learn more about your options or receive assistance, contact resources like Winters Heating Cooling.
