Do not bag or cover a heat pump outdoor unit in winter. It must breathe, including during defrost. A cover left on blocks the air the coil needs, traps the water the defrost has just made, and can stop the unit or soak the electrics. Clear leaves off the cabinet. Leave the coil open. If you go away, switch the system off at the controller if you wish, and still leave it uncovered. A plastic winter cover sold online is still a cover.
Frost on the coil, and water out of the base
A reverse-cycle split is an air-to-air heat pump. In heating it takes heat from outdoor air, so the fan and the coil have to see that air. Frost builds on the coil. The unit defrosts by melting it. Water runs out of the base. A bag over the top turns that into a wet, airless box. Cooling in a mild winter spell, if you use it, needs the same free air. The cabinet is weatherproof when it is installed as the manual shows. It is not weatherproof inside a sack. Do not bag or cover it. Defrost needs air and a way for water to leave. Leaves can be cleared by hand from the outside. Switching it off is fine. Covering it is not.
Snow, leaves and a curious animal are the usual motives. A manufacturer guard that the manual specifically allows, and that does not block the required openings, is a different object from a waterproof cover. If the manual does not list a cover, do not add one. Do not wrap the unit in insulation either. A roof, a carport or a small hood that keeps falling snow off the top can be fine when the sides stay as open as the manual requires. The test is breathing and service access, not whether the cabinet looks protected. A snow hood is acceptable only if the manual allows that guard and the air openings stay as the manual requires. A general waterproof cover is not a snow hood. If you only use the unit for cooling in summer, still do not seal it in a cover. Switch it off if you want it idle, keep leaves off, and leave the coil able to breathe. A sealed bag holds moisture.
A soaked cabinet that was run under a bag
Take the cover off before anyone runs the system. Let the cabinet dry if it is soaked. If it was run while covered and now trips, smells of burning, or will not start, leave it off and book a service. Do not open the refrigerant circuit. F-gas rules apply when a certified company has to work on the gas. A cover mistake is not, by itself, a gas job. Planning Portal rules still decide where the unit stands. They do not ask you to wrap it.
Core buying guides
Start with these high-intent guides, then dig into the rest of the library.
Related guides
Sources and further reading
How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.