Heat pumps

Heat pump installation in Milford

Most Milford homes already heat with a heat pump. Whether you are adding one or replacing an old unit, the electrical work and the position of the outdoor unit decide how safely it runs and how well it copes with living near the sea.

Technician in blue overalls and gloves working on a heat pump outdoor unit beside a house

How Milford heats its homes

At the 2023 Census, Stats NZ counted a heat pump in use in about two in three occupied homes across Milford's two census areas, Milford West and Milford Central, in line with the country as a whole. More than four in ten homes also used electric heaters, and in Milford Central almost a third used a fixed gas heater, more than three times the national rate. Homes can use more than one kind of heating, so those figures overlap, but the picture is clear: most Milford households already know what a heat pump does, and plenty still have rooms heated by a plug-in heater.

Heat pumps move heat in from the outside air using electricity, which is why EECA describes them as an efficient way to heat a home. That efficiency depends on the installation: the right size of unit, the right place for each part, and an electrical supply that suits it. The electrical side is where we come in.

An outdoor unit that has to live by the sea

Much of Milford is close enough to the sea for salt to matter. BRANZ puts land within 500 metres of the coast, and within 100 metres of tidal estuaries such as the Wairau, in its highest exposure zone for wind-driven salt, and a heat pump's outdoor unit is a metal cabinet wrapped around finned coils that sits out in it all year. The EECA good practice guide to heat pump installation says coastal installations need corrosion protection for both the outdoor cabinet and the coils, and that outdoor units should be protected from sea spray, sheltered from strong wind, mounted on corrosion-resistant fixings, typically stainless steel, and given at least 600 millimetres of clearance for servicing.

In practice that means asking about a coastal-protected model before you buy, and choosing a spot on the lee side of the house rather than the wall that faces the beach. It also rules out some convenient places: the guide says not to put an outdoor unit under the house or a deck, where it cannot breathe.

The electrical work in a heat pump installation

A circuit that can carry it

Depending on the unit's rating and your existing wiring, a heat pump may run from an existing circuit with enough spare capacity or need a dedicated circuit back to the switchboard. In a new building it gets a dedicated circuit.

A lockable isolating switch

Mounted on the house, not on the outdoor unit, and within reach for servicing, so a technician can lock the power off while they work. Fixing the switch to the unit itself is not allowed.

Connections sealed against weather

Cable glands or flexible conduit where the supply enters the outdoor unit, which matters all the more in salt air. A corroded isolator is one of the leaks that electrical fault finding can turn up.

A certificate on completion

EECA's guide says all the electrical work must be done by a registered electrician with a Certificate of Compliance issued at the end, and warns that unlicensed electrical work can void house insurance.

Apartments and townhouses

Milford has a good number of apartment buildings and townhouses, and they bring rules of their own. EECA's guide warns against putting an outdoor unit on a balcony or deck more than a metre above the ground below if it would help a child climb over the balustrade, and any screen around the unit must not give a foothold. Before choosing a spot on an exterior wall, a roof or a shared courtyard, check the building's rules with the body corporate, and allow for the cable route from your own switchboard. If the board is already full, a switchboard upgrade may need to come first.

Heat pump questions

Can a heat pump run off an existing power socket circuit?

Sometimes. EECA's guide allows a heat pump to be connected to an existing circuit if it has enough spare capacity, and calls for a dedicated circuit in new buildings. Which one your house needs depends on the unit's rating and what else is on the circuit, and we check that before the unit goes on the wall.

Why does Auckland's mild climate matter when sizing a heat pump?

Heat pumps are sized for the coldest outdoor temperature they are expected to work against. EECA's guide gives an external design temperature of 1 degree for the Auckland Council area, against minus 4 for Christchurch and Dunedin, so a unit sized for a Milford living room is not the one you would choose for the same room in Canterbury.

What does coastal protection mean for the outdoor unit?

A protective treatment on the outdoor cabinet and the heat exchanger coils that slows corrosion from salt. EECA's guide says coastal installations need it for both, so ask whether the model you are buying has it, and keep the unit clear of leaves and debris.

We still use plug-in heaters in the bedrooms. Can a heat pump replace them?

Often, yes. The questions are whether the room suits a wall unit, where the outdoor unit can go, and whether the switchboard has room for another circuit. We look at all three on one visit.

Will I get a certificate for the electrical work?

Yes. The electrical connection of a heat pump is prescribed electrical work, it is tested on completion, and you receive a Certificate of Compliance. Keep it with the unit's manuals and warranty.