Why Wellington heat pumps need looking after
Salt from the harbour and south coast
Under the NZS 3604 maps, as BRANZ summarises them, Wellington homes within 500 m of the coast, harbour included, are in exposure zone D for sea-spray salt. BRANZ's testing found ocean winds can carry salt particles more than 20 km inland.
Wind that delivers it
Wellington Airport records gusts over 63 km/h on 166 days a year. Temperzone's yearly maintenance list for Hitachi systems includes clearing lint and dust off the outdoor coil fins and touching up damaged paintwork to stop corrosion.
A heat pump that works all winter
Wellington Aero averages 1,625 heating degree-days a year, and 53.59% of the city's homes used a heat pump as a main heater in the 2023 Census. BRANZ says filters on a heat pump used frequently should be cleaned several times a year.
Damp air indoors
Mean 9 am humidity at the airport peaks at 81.1% in June and July (NIWA). If the indoor unit smells musty, Samsung NZ suggests airing the room, running Fan mode for 3 to 4 hours, cleaning the drain and washing the filters, and says a smell that persists may need professional cleaning.
How often to book one
While the warranty runs, the brand sets the interval. For a standard home system, Mitsubishi Electric NZ's minimum is a yearly service. Rinnai NZ wants yearly maintenance by its authorised service centre and says missing it during the warranty may void it. BRANZ suggests a service check every 2 to 3 years.
Near the sea, corrosion is mostly your responsibility under the warranty. Rinnai NZ makes the owner responsible for extra corrosion protection in sea air, MHIAA says the same for coastal sea air, and Samsung's NZ warranty excludes damage from salt spray. BDT, which issues Mitsubishi Electric's NZ warranty, says corrosion isn't a manufacturing defect where protection wasn't correctly specified, applied or maintained.
So keep every service record. It's your evidence that the protection was looked after.
What a service near the coast should include
- The outdoor coil and fins cleaned of salt, lint and grime.
- Paintwork and any corrosion coating checked, and touched up where damaged.
- Indoor filters, coil and drain tray cleaned.
- The drain line checked so water reaches a drain or garden.
- The bracket and its fixings checked on an exposed wall.
- A dated written record of what was done and found.
Ask before you book
- Does my brand's warranty accept your servicing?
- How often do you service units this close to the sea?
- Will you check the corrosion coating, not just the filters?
- What will the written record include?
Between services
You can
- Clean the filters as your manual says; a busy winter may mean several times.
- Wash the outdoor unit with car wash liquid and a hose, as Mitsubishi Electric NZ suggests every 6 months.
- Keep plants and stored gear well clear of the outdoor unit.
- Write down any smells, drips, noises or error codes for the technician.
Leave to a licensed installer
- Anything behind either unit's covers.
- Cleaning the coils, drain tray and drain line.
- Refrigerant checks and leak repairs.
- Corrosion treatment and paint touch-ups.
What we'd do
How we'd handle it near the water
Within reach of the harbour or south coast, we'd book a service every year, warranty or not, and keep each invoice as proof the corrosion protection was kept up. Further from the sea, we'd follow the brand while the warranty runs, then let how hard the unit works decide. Either way, we'd want a heat pump servicing specialist who sees salty outdoor units every week.