Cleaning a heat pump: filters, coils and drain

What can you clean yourself?

Think of the safe jobs as the ones that need no tools and no access to the sealed system. They are:

• Washable filters in a wall-mounted indoor unit, or the disposable filter in a ducted air handler.
• The outside of the indoor unit, with a soft dry or slightly damp cloth.
• Leaves, grass and snow around the outdoor unit.
• Loose dirt on the outdoor coil, removed gently.

Always switch the system off at the thermostat or remote first, and switch off the outdoor disconnect before touching the outdoor unit. Cleaning is part of regular maintenance, and the routine is close to what you would do for an air conditioner. A clean heat pump running with free airflow uses less energy. The full seasonal routine is in our heat pump maintenance checklist.

How do you clean the indoor filters?

Open the front panel of a wall or ceiling unit, slide the filters out, and vacuum off the dust. If they are very dirty, rinse them in lukewarm water with a little mild soap, then let them dry completely before putting them back. Never run the unit without its filters. Ducted systems usually use a replaceable filter in the air handler or return grille, and a clogged one cuts airflow, raises running costs and strains the blower.

The right interval depends on dust, pets, smoking, renovations and season. Many manuals suggest checking every month or two while the system is working hard. Follow the manual for your model, since cleaning instructions differ between ductless systems explained in ductless heat pump guides and ducted units.

How do you clean the outdoor unit?

Turn off the power at the disconnect, then clear leaves, cobwebs, seeds and cottonwood fluff from the grille and base. A garden hose at low pressure can rinse the fins gently, spraying from the inside out if you can reach, or straight on from the outside. Do not use a pressure washer, a wire brush or a sharp tool, because the aluminum fins bend and cut easily, and bent fins restrict airflow.

Keep clear space on all sides, usually at least several tens of centimetres, and follow the installer’s clearance instructions. In winter, brush snow off the top and sides and clear drifts and ice around the base. Do not wrap the unit in a tarp, because it traps moisture and invites pests. For normal frost and defrost behaviour, see defrost cycles and noise.

What about the indoor coil and condensate drain?

A dirty indoor coil or blower wheel needs more than a wipe. Accessing them usually means removing panels, and harsh cleaners can damage parts or leave residue, so this is best left to a technician. The same goes for a drain line that is clogged or leaking. A visible water drip, a musty smell or algae-like slime inside the unit suggests moisture buildup, and a technician can clear the drain and treat the coil safely.

What should you leave to a technician?

Anything that involves refrigerant, electrical components, the sealed system or an internal coil needs a licensed person. So does persistent ice, odd noises, poor heating or cooling and error codes. Our guide on when to call a heat pump technician lists the signs, and what a service visit covers shows what to expect and how often.

If the system is old and repairs mount up, the repair or replace decision guide helps you weigh the next step.

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