How to Clean Your HRV

You've just moved into a new home. To your surprise, the air smells fresh even though the building has been closed for a while. You notice a large rectangular device on the outside wall and wonder what it is. What you're looking at is the heat recovery ventilator (HRV) that's constantly removing stale air and replacing it with filtered fresh air. This system is an essential feature for keeping the air fresh in sealed and insulated homes.

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What Is a Heat Recovery Ventilator (HRV)?

Heat recovery ventilators serve two purposes. Firstly, the unit continually refreshes the air in the home and, at the same time, removes stale air. Additionally, it has a clean air exchanger that recovers heat energy from the stale air and transfers this energy to the incoming air. This prevents energy loss and reduces the load on the HVAC system.

How Does It Work?

A heat exchanger inside the HRV separates stale air from fresh air. In cold weather, stale air is warmer than the incoming fresh air. As the stale air passes through the core, it transfers heat energy to the cold air on the other side of the heat exchanger core. This process heats the fresh air, which reduces energy loss and the load on the furnace. In summer, the HRV works in reverse.

What's the Difference Between an HRV and an ERV?

An HRV has a straightforward heat exchanger that transfers energy, known as sensible heat energy, from the outgoing air to the incoming air. However, stale air also contains latent heat, which is energy contained in the moisture in the air. To recover this latent energy, an energy recovery ventilator (ERV) has a different core made from a porous material. This material allows the moisture to permeate through the core into the incoming airstream. This facilitates the transfer of latent heat as the fresh air picks up the moisture. ERVs recover more heat energy than HRVs.

HRV Maintenance Guide

HRVs and ERVs need regular maintenance, including cleaning or replacing filters, and removing dirt and debris. Here's how to perform routine HRV maintenance.

Disconnect the Electrical Power

The HRV should have a separate power supply fed from the breaker box. Identify the correct circuit breaker and switch it off. Check there's no power at the HRV unit.

HRV Filter Cleaning

Every few months, access the air filters by removing the HRV door. Remove the two filters, one on the incoming air duct and one on the stale return air duct. Inspect the filters for damage and clean them with a brush and vacuum. Don’t wash the filters unless they're washable; check your manual for details. Replace contaminated, dirty or torn filters.

Check and Clean the Exterior Vents

Inspect the outside vents and remove leaves or other debris. Make certain the vents aren't obstructed by trees or bushes. Clean the exterior screens and replace them when dry. During winter, make certain there's no ice or snow buildup. If the outlet has a back-draft damper, check that it moves freely and lubricate it, if necessary.

Clean the Heat Exchanger Core

Twice a year, carefully remove the heat exchanger core and inspect it for damage. Handle it carefully to avoid damaging the fins.

Clean the HRV core. Use a brush to remove dirt or fluff. Wash the HRV core using a garden hose and sprayer. Don't use a high-pressure washer, as this could damage the fins. Allow the core to dry before reinstalling it. Make sure to install it with the correct orientation.

Cleaning an ERV core. Clean the ERV core with a brush and vacuum, but never wash it, as this will damage the soft material. You should only service the ERV core in warm, dry weather.

Clean the Drain Pan and Check the Condensate Drain

Every 6 months, check the HRV condensate drain. Check that water flows freely through the pipe by pouring some water onto the pan leading to the condensate drain. If necessary, use a piece of wire to remove blockages such as mold or dirt. Clean the condensate pan.

Service the HRV Fans

Clean the blower fans using a soft brush. Sealed fans don't generally require lubrication.

Clean the Grills

Once a year, clean the air extraction and delivery duct grills to remove fluff, dirt and grease.

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Annual HRV Maintenance by an HVAC Contractor

Every year, contract an HVAC or HRV specialist to service the unit. Make certain the contractor has accreditation to service HRVs and ERVs. It's recommended you arrange for an HVAC service at the same time.

HRV Duct Cleaning and Inspection

The technician should thoroughly inspect the ductwork connected to the HRV. They will check the duct insulation and repair any punctures in the insulation jacket to prevent condensation. It's recommended that the contractor clean the ductwork internally every 2 years.

Check the System for Correct Operation

The contractor checks the controls for proper operation. They should calibrate the humidistat, if fitted, and check the heat exchanger defrost system functions correctly. They inspect the wiring and connections to make certain these are secure.

Balance the System Airflow

An HRV system must have a balanced air flow. This avoids indoor air quality problems and prevents over- or under-pressurization of the home. To do this, the contractor carefully measures the incoming and outgoing airflow to verify they're the same. If needed, they adjust the airflow using the dampers to achieve a balance. They must record this information on the HRV maintenance label.

Troubleshooting FAQs

Use these FAQs to troubleshoot your HRV.

Why Is Not Air Coming Out of My HRV?

If the unit runs, but there's no air coming out, you may have a blocked filter and need an HRV filter replacement. Other reasons include a blocked inlet or outlet vent and damaged ductwork.

What Do I Do if My HRV Is Frozen?

If the core of the HRV freezes, open the access door and allow the core to defrost. If possible, remove the core and thaw it in your sink. Refer to the instructions in the owner's manual to discover how to check the defrost mechanism, or call a contractor.

Why Is the Air From My HRV so Dry?

If the air in the home feels dry in winter, check the setting on the humidistat. If this doesn't help, run the HRV intermittently or on its lowest setting. You may need an ERV if these changes don't resolve the problem.