How to Clean the Filters and Core on an Air Exchanger

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Whole-house ventilators, like air exchangers, energy recovery ventilators (ERV) and heat-recovery ventilators (HRV) need routine cleaning because the air pulled into these units carries a build up of dust and debris with it — creating a not-so-ideal situation for your air quality. Air exchangers, ERVs and HRVs contain air filters to trap larger contaminants, but some of the dust slips through and settles inside the core, which directs airflow in very specific patterns to facilitate proper ventilation, heat exchange and/or humidity control. Because of this, the core needs to be removed and cleaned on a regular basis, as do other parts in the whole-house ventilation system.

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If this maintenance task is neglected for too long, the entire system has to work harder to pull air past the clogged filters. Efficiency decreases, indoor air quality suffers and the unit itself may need to be replaced sooner rather than later. Fortunately, cleaning an air exchanger, HRV or ERV unit is an easy DIY task that homeowners of any skill level can accomplish. All you'll need is a vacuum and some cold water.

How to Clean an Air Exchanger

Step 1: Remove the Core and Filters

Start by unplugging the unit from the wall or turning off its power supply switch. To open the access door, locate the clips under the unit, pull up to disengage them and lift the door all the way up. If needed, remove the door entirely by lifting it just 90 degrees and then pulling it straight up off the hinges.

Locate the large, diamond-shaped core on one side of the unit. Slide it straight out to remove it. Some ERVs have filters that attach to the core. If this is the case, you'll typically see foam filters on top of a pleated paper filter.

Air exchangers and HRVs are more likely to have filters not attached to the core. Note the four flexible ducts that emanate from the whole-house ventilation unit: a return air duct and a supply air duct for outside the home and a return air duct and a supply air duct for the inside of the home. Both pairs of ducts have their own rectangular-shaped filter. These slide straight out from the unit.

Step 2: Clean the Filters and Core

Using either a shop vac or a household vacuum cleaner, gently remove as much dust and debris from the ERV or HRV filter and core as possible. Set aside the pleated paper core (if applicable) after vacuuming.

Next, rinse the foam, plastic or metal filters with cold water. Do not get pleated paper cores wet or they'll need to be replaced entirely. Plastic cores, such as those in air exchangers or HRVs, can also be rinsed.

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Alternatively, soak the core and filters for a couple of hours in water mixed with a dab of mild soap. After soaking in soapy water, give the filters a final rinse with clean water. Let each piece air dry completely, as installing wet filters or cores into the ventilator can damage it. Accelerate drying by gently shaking off excess water.

Step 3: Clean the Unit, Registers and Vents

While the filters air dry, tidy up inside the unit by vacuuming the larger pieces of debris. Remove dust particles that are too fine for the vacuum cleaner by wiping down the unit with a moist towelette.

Locate the indoor air intake registers around your home. Vacuum them to remove accumulated hair, pet fur and dirt that would otherwise end up clogging the filter inside the air exchanger. If you have pets that shed a lot or your family tracks in a lot of dirt, install a filter behind each indoor intake register. Periodically wipe down or replace these filters for best results.

Finish by taking the vacuum cleaner outside and using it to remove any debris trapped in the outdoor air intake vent. Install a cover for this vent if you repeatedly find large debris inside the unit, like leaves or maple tree "helicopter" seeds.

Step 4: Reinstall the Filters and Core

After cleaning inside the unit, you can reinstall the fully dried filters and core. Start with the filters. Tuck them into their pockets on the side of the core or slide them into the grooves in front of the ducts inside the unit.

To replace the core, start by orienting it correctly. The front of the core should feature an arrow. Make sure that arrow faces you and points upward when placing the core inside the unit. Locate the grooves that hold the core in place and slide it in.

With everything clean and back where it should be, close and latch the door. Finally, plug in the unit or turn on the power switch.

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How Often to Clean a Ventilator

The ideal schedule for cleaning an air exchanger, HRV or ERV will vary from household to household. The general recommendation is to clean the unit, filters and core every three months. Lifestyle factors, like the number of people living in the home, the number of shedding pets in the home and how much dirt gets tracked in, will affect how quickly the indoor air intake filter gets dirty. Outdoor characteristics, like the presence of dust or leaves coupled with weather, could cause the outdoor air intake filter to clog more often.

Start by cleaning your whole-house ventilation unit on a three-month schedule. If the filters, core and unit are already filthy by that time, wait just two months until the next cleaning. On the other hand, if everything still looks clean after three months, inspect it on a monthly basis to see when it gets dirty enough to warrant cleaning. By the time six months have passed between cleanings, go ahead and spray down the filters and core anyway since some dirt has surely accumulated even if it's not very noticeable.

When to Buy a New Filter

Reusable air exchanger, HRV or ERV filters are made of plastic or paper, and they don't last forever. During routine cleanings, inspect the filters for broken pieces. Replace the filters if you find any defects. Check for a model number on the filter itself to purchase the correct design.

Nonreusable air exchanger filters are made of pleated fibers, foam or charcoal. These cannot be rinsed cleaned, so you'll need to purchase a new pair when it's time for your unit's regular cleaning. Because they come in different sizes to accommodate different units, measure the old filter to ensure you purchase the correct replacement.

Don't hesitate to reach out to an HVAC professional if you're not sure what's best for your unit. The current filter in your air exchanger may not even be the most effective one. If you're unhappy with the filter's performance, a pro can advise you about solutions.

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Cathy Habas enjoys distilling even the most complicated home improvement tasks into bite-sized pieces. She believes in empowering homeowners one article at a time.