Air-source heat pump quarterly maintenance checklist

Building contact told before modes are forced

Occupants or the building contact told the unit will be run in the off-season mode and through a defrost, so cold air in winter or warm air in summer is expected.

Controls found in normal heat pump mode

As found, thermostat or controller in normal heat pump operation, emergency or backup heat not left forced on, schedule and setpoints noted before any testing.

Return filters checked and seated

Filter clean, correct size and fully seated with no air bypassing around a loose frame, gasket intact at the indoor unit.

Indoor, outdoor and any backup heat circuits locked and tagged

Every feed locked and tagged before a panel opens: indoor unit, outdoor unit and any backup heat circuit; panels refitted and locks lifted by whoever hung them before the run checks.

Indoor coil face and drain pan checked

Coil face clean and not iced, blower wheel free of buildup, pan draining with no standing water.

Outdoor coil and fan clearances checked

Coil fins clear front and back, fan spins freely, required air clearance around the cabinet not blocked by storage or growth.

Base drainage and defrost meltwater path checked

Base pan drain holes open, no ice dam at the feet of the unit, meltwater running away from the pad.

Outdoor unit mounting sound and clear of snow and roof runoff

Stand, bracket or pad sound, level and anchored, coil held above the snow the site gets, and no gutter, eave or roof edge dripping onto the coil to freeze.

Heating and cooling changeover observed

Unit commanded through both modes, reversing valve shifting with the expected sound and a temperature swing at the indoor coil.

Defrost cycle observed or its evidence checked

A defrost initiated or recent evidence confirmed, outdoor coil clearing without the unit blowing cold air indoors on the changeback.

Outdoor temperature at the controls checked against a thermometer

Outdoor reading on the thermostat or controller compared with a thermometer at the unit, sensor shaded and clear of the discharge air, since lockout and staging run from it.

Controls put back to their as-found schedule and setpoint

Test holds cleared, mode, schedule and setpoints returned to what was noted at the start, no emergency heat left on, unit left running on its own call.

Season and mode tested recorded for the next round

Which mode was proven this visit, heating or cooling, entered against the unit so the next quarter tests the other one and nothing goes a full year unchecked.