Heat pump noise, what's normal and how to fix it
We repair noisy heat pumps, indoor and outdoor. A hum or the odd click is normal, but rattles, grinding and squeals usually mean something has worn or come loose, and most can be fixed.
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Normal heat pump noises
A healthy heat pump makes a few normal noises. Know them and you won’t go hunting for a problem that isn’t there:
- Hum or whirr: from the outdoor unit while the compressor and fan run. On an inverter unit it rises and falls as it speeds up and slows down.
- Air noise: from the indoor fan. It’s louder on high, quieter on low or auto.
- Hiss or whoosh: during defrost on frosty mornings. The outdoor unit switches over to melt ice off its coil, then switches back. Meanwhile the indoor fan takes a break.
- Clicks and creaks: from the indoor unit’s case as it heats up and cools down.
- Gurgling or trickling: gas moving through the pipes, or water draining off the coil.
- A click outside: relays and valves in the outdoor unit switching at start-up and shutdown.
If your noise is on that list and isn’t unusually loud, the unit’s doing its job.
Heat pump noises that point to a problem
Match what you hear to its likely causes before you take anything apart.
| Noise | Likely causes |
|---|---|
| Rattling | Loose panels or screws, a loose fan guard, debris in the fan, the unit moving on its feet or bracket |
| Buzzing | Vibration through the wall or bracket, a loose electrical connection, a failing fan motor or contactor |
| Grinding or scraping | Worn fan motor bearings, a fan blade catching on ice or a guard |
| High pitched squeal | Fan bearings or a motor on its way out |
| Banging or thumping | Ice hitting the fan, a loose compressor mounting, a unit that’s not level |
| Constant gurgle with poor heating | Possible low refrigerant charge, which needs a leak check |
| Loud water drips or bubbling indoors | A blocked or poorly sloped condensate drain |
Buzzing with a burning smell is serious. So is any noise with smoke. Switch it off at the isolator outside and ring us. Don’t keep running it.
Get a free quote. Installs, servicing and repairs on all major brands.
Heat pump noise and Christchurch neighbours
Outdoor unit noise is measured at your neighbour’s place, and Christchurch sections don’t all leave the same room.
- Infill sections. In Papanui, many original sections now hold two to four homes, with little room down the sides. The unit often goes on a wall bracket or a slim pad, so anti-vibration mounts and a spot away from next door’s bedroom matter more.
- Hillside homes. Sound carries differently on a slope. In Cashmere, a unit below a neighbour’s deck can bother them more than you’d think. We check what’s above and below before we move or remount it.
- Bedroom units that run all night. In Oaklands, a bedroom heat pump often runs overnight. Indoors, use the low fan setting. Outside, keep the unit off walls near the neighbour’s windows. Christchurch sets the noise limits at the neighbour’s site.
- Selwyn homes. In Prebbleton, heat pump noise comes under the Selwyn District Plan, not Christchurch’s. Where the outdoor unit sits still decides how much noise reaches next door.
- Frosty mornings. A hiss and a pause during defrost is normal. Hard frosts are part of a Hoon Hay winter, so raise the unit and keep its drain path clear. Ice that builds up in the base can catch the fan and bang.
Fixing a noisy heat pump outdoor unit
The neighbours hear the outdoor unit, so fix that first.
- Tighten everything: panels, screws, the fan guard and the electrical cover. A rattle is often just one loose screw.
- Anti-vibration feet or mounts: rubber feet under a unit on the ground, or isolation mounts on a wall bracket. They stop the hum travelling into the house and the ground.
- Level it: a unit that’s sunk on one side shakes more. Water can pool in the base too.
- Clear ice and debris: leaves, twigs and built-up ice can catch the fan. Clear the base drain so meltwater doesn’t freeze again.
- Service the fan and coil: a dirty coil makes the fan and compressor work harder. Worn fan bearings need replacing. Oiling won’t fix them.
- Quiet or night mode: some units have a setting that keeps the fan and compressor slower overnight.
- Move it: away from bedrooms. Out of corners where sound bounces. Off thin walls that act like a drum.
A screen can hide the unit and soften some of the sound. It needs open space round it, though. Read our heat pump covers guide.
Fixing a noisy indoor unit
- Filters: clean them. Clogged filters make the fan work harder, and it whistles.
- Louvres: turn the unit off at the isolating switch for a few minutes. That sometimes clears a louvre that ticks or sticks. If it keeps happening, the louvre motor may need replacing.
- Fan wheel: a dirty or unbalanced barrel fan hums and wobbles. It needs a professional clean.
- Drain: bubbling and gurgling indoors often means the condensate drain is blocked or doesn’t slope.
- Mounting: if the unit isn’t fixed tight to its back plate, it can buzz against the wall.
Heat pump noise on the energy label
The Zoned Energy Rating Label can show indoor and outdoor sound levels. Showing noise is optional in New Zealand. So some labels have it and some don’t.
The figures are measured at full output on cool. Most of the time, a unit runs quieter than its label shows. For comparison, a quiet home is about 30 dBA and a normal conversation is about 60 dBA.
Buying a new heat pump for a spot near a bedroom or a neighbour? Compare the outdoor sound figure across models.
Noise and the neighbours in Christchurch
Christchurch has no set distance a heat pump must be from the boundary. What counts is how loud it is at the neighbour’s place. The night-time limit is the one to watch. We’ve laid out the limits and the complaint process in our boundary rules and consent guide.
Getting a noisy heat pump fixed
We’ll find where the noise is coming from and fix it. We’ll also tell you if the unit would be quieter somewhere else. Ring 03 242 1023 or get in touch online.
Need this checked on your property? We fit, service and repair heat pumps across Christchurch. Free quote → · What size do I need? →
Questions about a heat pump making noise
Why is my heat pump rattling?
It's usually something loose. A panel or screw, or the fan guard. It might be a twig or other debris inside the outdoor unit. Or the unit has shifted on its feet or bracket. Switch it off at the isolating switch and look for anything caught in the fan. If you can't see anything, it needs a technician.
Is it normal for a heat pump to make a whooshing noise?
Yes, when it's defrosting. On cold mornings the outdoor unit runs backwards for a few minutes to melt frost off its coil. You'll often hear a hiss or whoosh as it switches over and back. Sometimes you'll see steam coming off it too.
Why does my indoor unit click or creak?
The plastic case grows and shrinks a little as it warms up and cools down. A few clicks and creaks when it starts or stops are normal. A constant tick or knock isn't. That can point to a problem with a fan or louvre motor.
My neighbour says my heat pump is too loud. What can I do?
Get it checked for worn fan bearings or vibration. Fit anti-vibration feet. Use a quiet or night mode. Or move the outdoor unit away from their bedrooms. In Christchurch the rules go by the noise at their place, not by distance. Our boundary rules guide has the details.
More on noise limits and repairs
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