Fixit: Clean, inspect ventilation system

Q What's an HRV and how do we care for it?

A HRVs, or heat recovery ventilators, are found in homes built in Minnesota since 2000 (and in many remodeled homes).

An HRV is a mechanical ventilation device that helps make a home healthier, cleaner and more comfortable by continuously replacing stale indoor air with fresh outdoor air. Sometimes called air-to-air heat exchangers, HRVs are set apart from other mechanical ventilation devices because they exchange heat between the streams of air coming in and going out, which reduces the cost of heating or cooling the healthy fresh air that circulates through the home.

Because there are several types and designs of HRVs, check for specific maintenance instructions in the unit's operating manual or ask the contractor who installed or services the HRV to demonstrate proper maintenance procedures.

In general, after disconnecting the electrical power:

• Clean or replace air filters, usually located within the HRV, every one to three months. Vacuum-clean washable filters and then wash with mild soap and water. Most washable filters will last several years.

• Vacuum or hand-clean any interior surfaces adjacent to the filters. If your unit has an electric preheater element, carefully vacuum the element's surfaces.

• Inspect the heat-exchange core twice a year and clean it as required (consult owner's manual for instructions). It's a good idea to inspect the heat-exchange core during very cold weather to ensure that the defrost mechanism is working.

• 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 2 or 3 quarts 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 keep air from entering the HRV.) Also clean the condensate pan inside the HRV.

• The fans on many HRVs are designed to operate continuously without lubrication. If lubrication is required, make sure you use proper motor lubricating oil (nondetergent oil). Inspect the blower fans periodically for dirt on the blades. Gently brush the blades or vacuum to clean.

• 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.

• Kitchen exhaust grilles should have filters to catch grease and should be cleaned regularly.

• Arrange for annual service by a contractor familiar with your HRV, ideally when you are having your furnace serviced.

From Canada's Office of Energy Efficiency's heat recovery ventilator publication.