Air exchangers: A mini maintenance guide

For your air exchanger to bring fresh air into your home and expel stale, humid air outside, each component needs to be thoroughly cleaned. But first, don’t forget to turn it off and unplug it.

How to clean or change the filters on an air exchanger

How often should you check the filters on your air exchanger? At least every three months. If your home is in a high traffic area or along a dirt road, or if you live in an area where many homes have wood stoves, you should check them more often. Same thing goes during allergy season.

Dirt or dust on or around your wall vent covers is often a good indicator of the general state of your filters. If the covers are dirty, it’s time to clean them! That includes the filters on your return air duct covers.

Reusable filters

• Remove the filters.
• Use a vacuum to remove any surface dust.
• Wash them with hot water and mild soap.
• Rinse well and let them drip dry before reinstalling.

Non-reusable filters

Some filters aren’t reusable and need to be changed. See the user guide to find out what kind of filter you’ll need to buy: foam, charcoal, pleated, etc. If you can’t find your user guide, remove the filter, measure the length, width, and thickness, and talk to a specialist to make sure you buy the right one.

Wondering if your filters are reusable? The fine folk at CAA-Quebec Advisory Services can answer your questions.

Be sure to:

• Place the filter securely in its frame, otherwise the air could go around the sides.
• Reset your exchanger if it’s equipped with a maintenance light.

How to clean intake vents

To protect the air exchanger’s components and optimize its performance, you’ll also need to clean the covers on your intake ducts.

Outdoor air intake

The surface of the outdoor air intake is much smaller than that of the filters. That means that even a partial obstruction of the cover will reduce your air exchanger to a gasping wheeze. You’ll want to check your air intake on a regular basis to remove any leaves, grass clippings, snow, or other detritus. Have the intake cleaned by a professional once every six years and after any major renovation. While you’re at it, have them clean the nearby exhaust vent.

Indoor intake vent

Clean the vent covers for your stale air exhaust on a regular basis. A tip for keeping dust and dirt from accumulating in the vent duct: add a filter behind the cover. Just be sure to clean it often so the air can flow freely. And check with the manufacturer to make sure this option will work with your setup. Another thing to note: any exhaust vent located in the kitchen needs a filter that catches grease.

How to keep your air exchanger running smoothly

Some of the components on your air exchanger, such as the recovery core, ventilator, drain pan, and exhaust duct, need to be cleaned at least once a year.

Heat or energy recovery unit

Be it polypropylene (plastic) or aluminum, the exchanger core should be cleaned every fall, before the heating season. Here’s what you’ll need to do:

1. Carefully remove the core.
2. Let it soak in warm, soapy water. Avoid very hot water. Powerful soaps and petroleum-based cleaners can also damage the core.
3. Let it drip dry completely before reinserting.

If you have an energy recovery ventilator (ERV), do not submerge the core or thermal wheel or clean it with water. Use a vacuum cleaner or air compressor instead.

Fan

The fan also needs to be cleaned without water. If the blades have stubborn, hard-to-remove grime, best to leave the cleaning to the experts. Even light pressure could unbalance the blades, which will affect the exchanger’s performance.

Drain pain and exhaust duct

Clean the drain pan and the inner surfaces of the exchanger with soapy water. You should also pour water into the trap from time to time to make sure the water is draining freely through the drain hose.

How to purge air exchanger ducts

Hard or soft, air exchanger ducts need to be cleaned with a special device designed for the twists and turns ducts make as they wind through your walls and floors. How often you need to clean them depends on what’s going on in the house. The ducts in a home with two adult smokers, two children, and a few long-haired cats and dogs will get dirty pretty quickly. Same thing goes for a home that’s undergoing major renovations. Take a look inside the exchanger or on the diffusers—that will give you a good indication of how dirty the ducts are. If you see any pleated ducting that’s become stretched out, it will need to be replaced.

How to balance an air exchanger

To supply your home with clean, fresh air, your exchanger needs to pull in and expel an equal volume of air, otherwise it could pressurize or depressurize your house. In the former case, humid air could be pushed into the building envelope, leading to mould build-up. In the latter, smoke from a chimney or polluted air from the garage could be drawn into the home.

Such imbalances are rare, but if you suspect something may be off, you can check for yourself with a garbage bag:

1. Place the bag on the mouth of the outdoor exhaust vent.
2. Time how long it takes for the bag to fill with air.
3. Then put the bag on the intake vent.
4. Time how long it takes for all the air to be sucked out.

Compare the results and, if there’s a significant difference between the two, talk to an A/C and ventilation specialist.  

Thanks to Frigo Temp inc. and FixAC, members of CAA-Quebec’s approved residential suppliers network, for their help with this article.