Heat pump in winter: what is normal and when to call for service
Steam above the unit and frost on the fins are usually normal heat pump behaviour. Here is what we hear about on the service line during cold spells and which symptoms point to a real fault.
When a cold spell hits Wielkopolska, the phone on our service line does not stop ringing. Plenty of those calls, though, are about things that are just a heat pump doing its job. We have written down the most common questions from the last few weeks, so it is easier to tell normal behaviour from a fault. If anything in the second half of this post matches what you are seeing, call straight away.
What is normal
Clouds of steam above the unit
This is the number one reason people call. In winter, frost builds up on the outdoor unit's heat exchanger. Every so often the heat pump runs a defrost cycle: for a few minutes it reverses the circuit and warms the exchanger, and the ice melts and turns to steam. From the street it looks like smoke from a chimney. It is not a fire or a leak, just water vapour.
Defrosting is most frequent at around 0 to +3 °C with high humidity, not in the hardest frost. In foggy, damp weather a cycle every 40-60 minutes is nothing unusual.
A change in sound, hissing, a moment of silence
During defrost the fan usually stops and the four-way valve switches the circuit. You may hear hissing or the rush of refrigerant, sometimes a single click. After a few minutes the fan starts again, often at higher speed. In frost the compressor runs harder, so the unit is louder than in autumn. That is normal too.
Radiators or floors briefly cooler
During defrost the heat pump borrows a little heat from the system. The flow temperature drops for a few minutes. With underfloor heating you will not notice; with radiators you sometimes will.
A thin layer of frost on the fins
Frost that builds up and clears after each defrost is fine. In damp weather the fins can stay white for most of the day.
The backup heater kicks in during hard frost
Heat pumps are usually sized so that below a certain outdoor temperature, most often around -7 to -10 °C, an electric heater helps out. Higher electricity use on the coldest nights is part of the design. The heater may also run during the anti-legionella cycle in the hot water tank. If the heater is running at +5 °C, though, something is set up wrong.
A higher bill in January
In frost the heat pump needs more energy for the same amount of heat, and the house loses more heat. January can cost two or three times as much as October. What counts is the total for the season.
What is not normal
A block of ice that grows day by day
If the bottom of the exchanger and the drip tray keep icing up and the ice does not clear after defrosting, the condensate drain is the usual culprit. A frozen pipe, or a drain that empties onto paving instead of into a soakaway, leaves the water nowhere to go. The ice can eventually reach the fan blades and damage them. This needs a service visit.
An error code on the controller
Take a photo of the display with the code and note when it appeared. Do not reset the controller several times in a row. The code tells us which parts to bring, and repeated resets sometimes wipe the error history.
The house is cooling down even though the pump is running
If the indoor temperature keeps falling for several hours while the heat pump runs, or sits idle with no message, call us. It could be a failed sensor, a heating curve set too low or a flow problem in the system.
A breaker that keeps tripping
If the breaker for the heat pump or the heater trips more than once, that is always a service call. Do not keep switching it back on.
New, unusual noises
Metallic scraping, the fan knocking against ice or a loud hum that was not there before can all mean damage. A short video on your phone helps.
What you can do yourself
- Clear snow around the unit and keep at least 30 cm free at the sides and back.
- Knock snow off the canopy above the unit, if it has one.
- Do not cover the unit with a tarpaulin or plastic sheet.
- Do not chip at ice with sharp tools. The fins bend easily and refrigerant pipes can be punctured. If you have to, pour lukewarm water over the ice with the unit switched off.
- Check that the condensate outlet is not buried in snow.
- Do not drop the indoor temperature by several degrees overnight. In the morning the heat pump then has to catch up at full output, often with the heater.
How to report a fault
The service line, +48 000 000 001, is open Monday to Friday, 7:00-19:00. Service contract clients also have emergency cover from October to April, daily 7:00-21:00. We treat "no heating" calls as a priority and usually come out the same day.
Have this ready:
- the unit model and serial number from the rating plate,
- a photo of the error code or controller screen,
- the indoor and outdoor temperature,
- a description of what changed and since when.
With that, our dispatcher can often sort the problem out over the phone. If not, the engineer arrives with the right parts.
A service before the season
Most winter breakdowns we see could have been caught earlier: a blocked condensate drain, a dirty heat exchanger, low system pressure, a badly set heating curve. A service visit in September or October costs less than one urgent call-out in January.
