How to Service Your Heat Pump Before Winter

A heat pump is one of the hardest-working appliances in a New Zealand home, and winter is exactly when you need it to perform at its best. Skipping pre-winter maintenance is one of the most common — and costly — mistakes homeowners make. A little time spent in late autumn can mean the difference between a warm, efficient home and an expensive breakdown in the middle of a Southland frost or a wet Wellington week.

Why Pre-Winter Servicing Matters

NZ winters bring sustained cold snaps, high humidity, and in coastal areas, salt-laden air that accelerates corrosion on outdoor units. A heat pump that hasn't been serviced may struggle to reach set temperatures, run longer cycles, and consume significantly more electricity — all while delivering less comfort. Energywise notes that heat pumps are among the most energy-efficient heating options available, but only when they're properly maintained. Dirty filters alone can reduce efficiency noticeably and degrade indoor air quality.

Regular servicing also extends the life of your unit, protects your warranty, and keeps your home compliant with Healthy Homes Standards if you're a landlord.

What You Can Safely Do Yourself

Most routine heat pump maintenance is straightforward and doesn't require a licensed technician. Here's what homeowners can tackle:

Indoor Unit (Head Unit)

• Clean the air filters — This is the single most important task. Remove filters (usually a simple clip or slide mechanism), vacuum off dust, then wash gently with warm water. Allow to dry completely before reinserting. Aim to do this every 4–6 weeks during heavy use.
• Wipe down the unit casing — Use a damp cloth. Avoid harsh chemicals that can damage plastic.
• Check the air vents and louvres — Make sure nothing is blocking airflow (furniture, curtains, stored items).
• Run a test cycle — Switch to heating mode and confirm the unit reaches your set temperature within a reasonable time.
• Check for unusual smells or noises — Musty odours often indicate mould on the evaporator coil; rattling may signal a loose panel or fan issue.
• Inspect the condensate drain — In heating mode this is less active, but a blocked drain from summer use can cause issues. Check the drain tray is clear.

Outdoor Unit (Condenser)

• Clear debris — Remove leaves, grass clippings, and dirt from around and inside the unit. Keep at least 30 cm of clearance on all sides.
• Rinse the coil fins gently — Use a garden hose on a low-pressure setting to wash away dust and grime. Never use a high-pressure washer — it bends the delicate aluminium fins.
• Check for corrosion — Coastal homeowners should inspect for salt corrosion on fins and casing. Sika and other suppliers offer coil-coating products, though application is best left to a technician.
• Ensure the unit is level — Settling ground can tilt the unit over time, affecting drainage and compressor operation.
• Check the refrigerant lines — Look for damaged insulation on the pipes running between indoor and outdoor units. Replace foam insulation if it's cracked or missing.

Season-by-Season Maintenance Checklist

Pre-Winter Checklist at a Glance

• ✅ Wash and dry air filters
• ✅ Wipe down indoor unit casing and louvres
• ✅ Clear 30 cm clearance around outdoor unit
• ✅ Rinse outdoor coil with low-pressure water
• ✅ Inspect refrigerant pipe insulation
• ✅ Check outdoor unit is level and secure
• ✅ Test heating mode — confirm it reaches temperature
• ✅ Listen for unusual noises or smells
• ✅ Check remote control batteries
• ✅ Review your unit's manual for model-specific tasks

Common Mistakes to Avoid

Using a high-pressure washer on the outdoor unit is one of the most frequent DIY errors — bent fins restrict airflow and reduce efficiency significantly. Always use a gentle hose.

Ignoring a musty smell is another. That odour usually means mould or bacteria on the evaporator coil, which gets blown into your living space. A professional clean with an appropriate coil cleaner (available at Mitre 10 or Bunnings) or a technician's fogging treatment will sort it.

Blocking the outdoor unit with a cover or stored items during winter is a mistake — the unit needs airflow even in heating mode, as it extracts heat energy from outside air.

Skipping the test run before winter hits means you won't discover a fault until you desperately need heat. Always do a test cycle in April or May.

When to Call a Professional

Some tasks are beyond DIY — and some are legally restricted. In New Zealand, refrigerant handling is restricted work and must only be carried out by a registered refrigeration and air conditioning technician. Topping up or recovering refrigerant without the correct certification is illegal and potentially dangerous.

Call a qualified heat pump technician if you notice:

• The unit isn't reaching the set temperature despite clean filters
• Ice forming on the outdoor unit outside of normal defrost cycles
• Refrigerant line insulation is damaged and you suspect a leak (hissing sound, oily residue near fittings)
• Error codes on the display panel
• The unit trips the circuit breaker
• Unusual grinding, rattling, or squealing noises
• The unit hasn't had a professional service in two or more years

A professional service typically includes coil cleaning, refrigerant pressure checks, electrical connection inspection, and a full performance test. BRANZ recommends professional servicing every one to two years for residential heat pumps, depending on usage and environment. Coastal and high-use installations may need annual attention.

For electrical faults, remember that any work on the fixed wiring or the dedicated circuit supplying your heat pump must be carried out by a registered electrician — see the Electrical Workers Registration Board for what constitutes restricted electrical work.

You can find qualified, local heat pump installers and service technicians on tradedirectory.co.nz — look for technicians with manufacturer authorisation or membership with the Air Conditioning and Refrigeration Association of New Zealand (ARANZ).

Sources & Further Reading

• Energywise – Heat Pumps
• BRANZ – Building Research
• Tenancy Services – Healthy Homes Standards
• Electrical Workers Registration Board – Restricted Work
• MBIE Building Performance
• Bunnings NZ – Cleaning & Maintenance Supplies