If your heat pump isn't heating or cooling as well as it used to, low refrigerant could be the culprit. While you can look for the telltale signs yourself, handling or topping up refrigerant is restricted work in New Zealand and must only be carried out by a licensed refrigeration and air conditioning technician. Here's what to look for and what to do next.
What Is Refrigerant and Why Does It Matter?
Refrigerant is the fluid that circulates through your heat pump, absorbing and releasing heat to warm or cool your home. Unlike petrol in a car, refrigerant isn't consumed during normal operation — it runs in a sealed loop. If levels drop, it almost always means there's a leak somewhere in the system, not just normal use.
Common refrigerants used in NZ heat pumps include R-32 and R-410A. These are regulated substances, and their handling is controlled under both NZ environmental law and industry licensing requirements.
Warning Signs Your Heat Pump May Be Low on Refrigerant
You won't be able to measure refrigerant levels yourself — that requires specialist gauges and training. However, you can watch for these symptoms:
- Reduced heating or cooling performance — the unit runs constantly but your room never reaches the set temperature
- Ice or frost forming on the outdoor unit — especially on the refrigerant lines or coils, even in mild weather
- Ice on the indoor unit's coil — you may notice reduced airflow or frost visible behind the front panel
- Hissing or bubbling sounds — these can indicate refrigerant escaping from a leak
- Higher power bills — a struggling system works harder and uses more electricity
- The unit blows air that isn't as warm or cold as expected — even after filters have been cleaned
- Error codes on the display — many modern heat pumps will flag a fault code; check your manual or the manufacturer's website
None of these symptoms alone confirms low refrigerant — they can also point to dirty filters, a faulty fan, or other issues. But if you notice several at once, it's time to call a professional.
What You Can Check Yourself First
Before calling a technician, rule out the simple stuff:
Clean or replace the filters
Dirty filters are the most common cause of poor performance and can mimic refrigerant symptoms. Most manufacturers recommend cleaning filters every 4–6 weeks during heavy use. Check your unit's manual for instructions.
Check the outdoor unit
Make sure the outdoor unit isn't blocked by vegetation, debris, or furniture. Restricted airflow reduces efficiency significantly.
Check the thermostat settings
Confirm the unit is set to the correct mode (heat or cool) and that the target temperature is sensible.
Look for visible ice
If you can safely see the outdoor unit's refrigerant lines (the insulated copper pipes), check whether they're frosted over. Some frost during cold mornings is normal and the unit will defrost itself — but persistent, heavy icing is a red flag.
| Symptom | Possible Cause | DIY Fix? |
|---|---|---|
| Weak airflow | Dirty filter | Yes — clean filter |
| Not reaching set temp | Low refrigerant or dirty coil | Call a technician |
| Ice on outdoor unit | Low refrigerant or airflow issue | Call a technician |
| Hissing noise | Refrigerant leak | Call a technician |
| High power bills | Multiple possible causes | Check filters first, then call |
Why You Cannot Top Up Refrigerant Yourself
In New Zealand, purchasing, handling, and recharging refrigerants is legally restricted. Technicians must hold the appropriate certification under the EWRB framework or relevant industry body, and refrigerant handling is governed by the Ozone Layer Protection Act and associated regulations. Attempting to handle refrigerant yourself is illegal, potentially dangerous, and could void your heat pump's warranty.
Refrigerant gases can cause frostbite on contact with skin, and some older types pose environmental risks. WorkSafe NZ provides guidance on working safely with hazardous substances in trade settings.
What a Licensed Technician Will Do
A qualified heat pump technician will:
- Connect manifold gauges to measure system pressure and compare it against the manufacturer's specifications
- Use an electronic leak detector or UV dye to find any leaks
- Repair the leak before recharging — simply topping up without fixing the leak is a short-term fix and bad practice
- Recharge the system with the correct type and quantity of refrigerant
- Test the system to confirm it's operating within spec
Always ask for a job sheet detailing what refrigerant was used and how much was added — this is good practice and helps with future servicing.
How Often Should a Heat Pump Be Serviced?
BRANZ and most heat pump manufacturers recommend a professional service every 1–2 years, in addition to regular filter cleaning by the homeowner. Catching a small refrigerant leak early is far cheaper than waiting until the compressor is damaged.
If you're a landlord, note that the Healthy Homes Standards require heating devices to be in good working order — a heat pump low on refrigerant may not meet compliance requirements.
When to Call a Professional
Call a licensed heat pump technician if:
- You notice any of the warning signs listed above after ruling out filter and airflow issues
- Your unit is displaying error codes you can't resolve
- You can see or hear signs of a refrigerant leak
- The system hasn't been professionally serviced in over two years
You can find qualified heat pump installers and service technicians in your area on tradedirectory.co.nz. Always check that your technician holds the appropriate certification to handle refrigerants.
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