What Dunedin does to a heat pump
Heating for most of the year
NIWA's degree-day table gives Dunedin (Musselburgh) 2,559 heating degree-days a year and only 22 cooling. The unit heats from autumn into spring, loading the filters and coil with dust for months.
Defrost duty on the Taieri
Dunedin Airport averages 66 days a year below 0 degrees, against 8 at Musselburgh. EECA says that below 5.5 degrees outside, a heat pump must divert some heating to defrost its coils, so inland units go through far more defrost cycles than coastal ones.
A city full of heat pumps
At the 2023 Census, 77.68% of Dunedin City homes used a heat pump as a main type of heating.
Why a service here comes down to salt, frost and access
Salt. The harbour, the peninsula and the ocean beaches put plenty of Dunedin homes in sea air. Mitsubishi Electric NZ says salt can speed up corrosion, that coastal systems may need servicing more often than yearly, and that keeping up any applied corrosion protection is the owner's job. Samsung NZ's warranty excludes damage from salt spray, sand and dust.
Frost. Frequent defrosting isn't a fault, but it means meltwater, ice and a coil that works hard. A service on an inland unit should look at how it drains and whether its spot traps cold air: Mitsubishi Electric NZ says units under houses or decking can create their own microclimate.
Access. Steep sections and two-storey villas put some outdoor units well up a wall. MHIAA, the distributor for Mitsubishi Heavy Industries, says its equipment must be safely reachable with a 1.7 metre ladder, and the owner provides any extra access.
What makes a Dunedin service bigger or smaller
The count of indoor units is the obvious one, since a multi-room system has several on one outdoor unit, and a ducted system adds a unit and filters in the roof space. Then it's how long since the last service, how close you are to the sea, and whether the filters were cleaned through winter.
A unit that's gone a few winters without attention will have more grime on its coils and drain tray. Ask for any corrosion work to be written up separately from the routine service, so you can decide on it. Haier's warranty booklet is one that asks owners to show service records when claiming, so keep each invoice.
Ask before you book
- Does my brand's warranty need a yearly service, and will your invoice record what was done?
- Will you clean the indoor coil and drain tray, or only the filters?
- How does the outdoor unit look after winter: corrosion, chipped paint, flattened fins?
- Is it defrosting more than its spot explains?
- Can you reach every unit safely, or do I need to arrange access?
Your part between services
You can
- Vacuum the filters as the manual says, more often in a winter of daily heating.
- Pull weeds and leaves back from the outdoor unit.
- Leave ice on the outdoor coil for the defrost cycle to clear.
Leave to a licensed installer
- Opening either unit to clean the coils and drain tray.
- Anything to do with refrigerant or the wiring.
- Corrosion treatment and paint touch-ups on the outdoor unit.
What we'd do
When we'd book it
We'd book late summer or early autumn, before the long run of heating starts, and follow the brand's interval while the warranty lasts. Near the harbour or a beach, we'd stay yearly after that too; for a lightly used unit well inland, a longer gap is fine if the filters stay clean. Registration-checked servicing specialists see the job, and only the one who takes it gets your details. Our heat pump servicing page explains what a service includes, and our Dunedin heat pump page has the rest of the city.