Routine Maintenance

If your HRV breaks down, hire a trained contractor to repair it (see “Finding a Contractor to Service Your HRV”). Do not avoid repairing the HRV simply to save money. If your home was designed and built to have an operating mechanical ventilation system, such as R-2000 homes or other airtight homes, poor indoor air quality, reduced comfort and moisture problems may result if the system is not properly operated and maintained.

Seven-Step Maintenance Schedule

With routine preventative maintenance, you can avoid unnecessary problems, ensure the effectiveness of your HRV, and prolong its life. The summary below indicates some general HRV maintenance requirements. Items 1 through 6 are maintenance procedures a homeowner should undertake between annual service visits by a professional.

For additional specific instructions, refer to your HRV operating manual or ask the contractor who installed or services the HRV to demonstrate the proper maintenance procedures. Some HRVs may have their maintenance instructions affixed to the heat-exchange core.

1. Clean or replace air filters. Filters, which are usually located within the HRV (see Figure 5), should be cleaned every one to three months. Some filters cannot be cleaned and should be replaced. Washable filters should be vacuumed first, then washed with a mild soap and water. Most washable filters will last several years before needing to be replaced.
   
   Dirty filters can reduce ventilation efficiency, result in unbalanced airflows, and even cause the unit to shut down if it is equipped with an airflow switch. Filters not designed to operate with your HRV can add resistance to the airflow and may impair the unit's operation.
   
   When cleaning the filters, take the opportunity to vacuum or clean any interior surfaces adjacent to the filters. As well, if your unit has an electric preheater element, carefully vacuum the element's surfaces.
   
   If the HRV uses the furnace ductwork to distribute fresh air to the home, you should also maintain the furnace filter and fan more frequently.

Figure 5
Example of location of filters in an HRV

2. Clear the exterior intake and exhaust vents of obstructions. Check the outside vents regularly to ensure that the screen openings are not obstructed by grass, bushes, leaves or other debris (see Figure 6). Do not replace the screen with mesh smaller than 1/4 inch, as this will block airflow. If the exhaust hood has a back-draft damper, check it for free operation and proper positioning (the damper should be closed when there is no airflow).
   
   You might want to check the hoods more often in the autumn (when there are leaves on the ground) and during the winter (to ensure that snow or frost build-up does not block the openings). Over time, you will become the best judge of how frequently you should check your HRV hoods. If the openings are regularly clogged or blocked, consider moving the vent openings higher up the wall.
   
3. Clean the heat-exchange core. Inspect the heat-exchange core twice a year and clean it as required (consult your owner's manual for instructions on inspecting and cleaning the core). A build-up of dust and dirt can restrict airflow and reduce the efficiency of your HRV. After inspection and cleaning, make sure the core is replaced right-side-up. It is also a good idea to inspect the heat-exchange core during very cold weather to ensure that the defrost mechanism is working.
   
4. Clean the condensate drain and pan. Twice a year, check the condensate drain (if your HRV has one) and tubing to ensure that they are open and free-flowing. To do this, find the hole that leads to the drain inside the unit. Then pour two or three litres of warm water into the pan leading to the drain. If the water does not flow freely, unblock the drain using a piece of thin wire. The tubing can be disconnected for cleaning. The condensate drain must have a “trap” – an S or loop in the tubing that traps a quantity of water – to prevent air from entering the HRV via this tubing (see Figure 1).
   
   You should also clean the condensate pan located inside the HRV.

Figure 6
Checking exterior inlets and outlets

5. Service the fans. The fans on many HRVs are designed to operate continuously without lubrication. Your owner's manual will indicate whether lubrication or service is necessary. If lubrication is required, make sure you use proper motor lubricating oil (non-detergent oil). Do not use too much oil, as this may damage the motor. Inspect the blower fans periodically for dirt on the blades, and remove it by gently brushing the blades or using a vacuum cleaner.
   
6. Clean the grilles and inspect the ductwork. Clean the duct grilles when they are dusty or greasy. At least once a year, visually inspect the interior surfaces of the ductwork leading to and from the HRV. These surfaces will collect dirt over time; however, professional ductwork cleaning is usually needed only once every few years.
   
   Kitchen exhaust grilles should have filters to catch grease. These filters must be cleaned on a regular basis or as required.
   
   Check for punctures in the insulation jacket (the protective cover that seals the insulation) on the fresh air and exhaust air ducts. Repair any punctures using foil duct tape. Otherwise, they can lead to condensation problems, including wet insulation, water on the floor and, occasionally, ice build-up. If the insulation itself is damaged, take the steps indicated in the HRV Troubleshooting Guide.
   
7. Arrange for an annual servicing. Your HRV should undergo annual general servicing by a contractor who is accredited by the Heating, Refrigeration and Air Conditioning Institute (HRAI) of Canada and who is familiar with your HRV. If possible, have your furnace and HRV serviced at the same time; this will result in less inconvenience and cost than two separate visits.

The HRV's annual servicing should include the following:

• maintenance items 1 to 6 (above). Additional requirements specified by the manufacturer should also be included.
  
• a general check for proper operation. Controls and electrical connections in the HRV should be inspected, particularly those located inside the exhaust and fresh air streams. The defrost system should also be tested.
  
• verification that the intake and exhaust airflows are properly balanced. Actual airflows should be measured and the results should be indicated on the maintenance label affixed to the HRV. If necessary, the airflows should be rebalanced.

The contractor should provide you with a written report on the overall condition of the HRV. Ask whether an extra fee will be charged before requesting such a report.

To help you remember when maintenance is due, an HRV Maintenance Chart is provided on the next page. Post a copy on the HRV to keep a record of your service and maintenance schedule.

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Source: Natural Resources Canada (NRCan) - Office of Energy Efficiency