Heat Pump Maintenance and Service – What You Can Do Yourself and What You Can’t

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Maintenance and service of a heat pump – what you can do yourself and what to leave to a professional

A heat pump is one of the most sophisticated devices in a modern household. Unlike a classic boiler, where the customer intuitively understands what is happening (gas is burning, water is heating), a heat pump operates on the principle of a refrigeration cycle – a compressor, expansion valve, evaporator, and condenser. This creates the impression of a black box for many owners: it either works or I call a service technician. In reality, the situation is much more nuanced. There is a whole range of tasks that are not only safe but also beneficial to do yourself – and at the same time, there are many interventions where DIY "help" will either void the warranty or pose a physical health risk.

In this article, I systematically go through the entire area of heat pump maintenance: what to do, when to do it, what to watch out for, and where the line is that only a certified technician should cross. I base my insights on practical experience with air-to-water and ground-to-water systems, from typical mistakes I see in customer cases, and from manufacturer documentation.

Why regular heat pump maintenance is important at all

This is a question I get from customers quite often, especially in the first few years after installation, when the device is working flawlessly. The answer has several levels.

First, performance. A heat pump operates with a temperature difference – the greater the difference between the heat source and the heating system, the higher the performance and simultaneously the higher the electricity consumption. Every dirt on the evaporator, every clogged filter, every air bubble in the circuit negatively affects this temperature difference. In layman’s terms: a dirty heat pump works harder at the cost of a higher electricity bill, while delivering less heat. This is reflected in longer running hours, a higher COP (or lower, which is worse), and a shortened lifespan of the compressor.

Second, warranty conditions. Most heat pump manufacturers require proof of regular service inspections for claims. If you don’t have this documentation, a claim can be rejected even for a clear manufacturing defect.

Third, safety. A heat pump operates with refrigerant (typically R32, R410A or newer R290/R454B), with electrical voltage up to 400 V, and in the case of ground-to-water systems, also with glycol mixture under pressure. Neglecting maintenance can lead to refrigerant leaks (environmental problem and health risk), electrical insulation faults, or bursting of pressure components.

Annual maintenance schedule – overview by season

A heat pump is not a seasonal device in the sense that it is turned off in summer – most modern units heat hot water year-round and many also have a cooling function in summer. Despite this, maintenance has its seasonal logic, because the unit experiences the most load during the winter peak and the best conditions for cleaning are in autumn or spring.

Spring (March – April): check after the winter load

After the heating season ends, it is an ideal time for a visual inspection of the entire system. That is when it is easiest to see what the winter load has done to the outdoor unit – especially with air-to-water systems.

Check the evaporator (finned heat exchanger) for damage. Stones, leaves, salt from road de-icing – all of this can get there during the winter.
Check the drip tray and drain hole. A clogged drip tray is a breeding ground for mold and corrosion.
Clean the area around the outdoor unit from vegetation that has grown during the winter.
Check that all service openings and covers are properly placed and undamaged.
Verify the operability of the protective heating cable on the drip tray – more on that below.

Summer (June – August): ideal time for a service technician

Summer months are typically the least busy in heat pump service. A service company will come faster, prices are usually lower, and any repairs won’t catch you in the middle of the cold. I recommend scheduling an annual professional inspection during the summer – checking the refrigerant circuit, measuring pressure balance, testing electrical components, and updating the firmware of the control unit.

Fall (September – October): preparation for the heating season

This is the most critical service point of the year. If something is wrong with the heat pump, you want to know it before the first frosty day, not when it is –10 °C outside and 16 °C inside.

Check the settings of the control unit – modulation times, heating curves, priority of DHW.
Deair the entire hydraulic circuit.
Check the pressure in the expansion tank.
Clean the filter/screen in the hydraulic circuit.
Check the anti-corrosion protection – inhibitor in the system.
Verify the functionality of the emergency heating (electric element in the tank or bivalent boiler).

Winter (November – February): only monitoring and emergency interventions

During the winter season, the system should run without interventions. Your task is monitoring – checking temperatures, power consumption, error codes on the display. If the unit shows frequent defrosting cycles, unusually long running times, or increased electricity consumption, note it down and contact service.

What you can do yourself: specific tasks step by step

Cleaning the evaporator of an air-to-water heat pump

The outdoor evaporator is a finned heat exchanger – it basically looks similar to a car air conditioner condenser. Outside air passes through these fins and transfers heat to the refrigerant. The fins are very thin (thickness 0.1–0.15 mm) and easily mechanically damaged, but chemically they are quite durable.

Use the following for cleaning:

Compressed air – blow in the direction from inside out (opposite to the airflow during operation). This way you will push out the dirt back out.
Garden hose with fine spray – without a pressure washer! A pressure washer (Kärcher and similar) deforms the fins and reduces the efficiency of the heat exchanger. I have seen dozens of damaged evaporators caused precisely by this.
Commercial evaporator cleaner (alkaline or acidic) – if the dirt is more severe, spray the cleaner, let it work for 5–10 minutes, and then rinse with water. Apply the cleaner from top to bottom.

Perform cleaning with the device turned off! Turn off the heat pump via the control unit and wait until the fan stops. It is also ideal to switch off the circuit breaker for the outdoor unit.

Cleaning filters and strainers in the hydraulic circuit

The hydraulic circuit (i.e., the water/glycol side) should have an installed filter with an insert (strainer). This filter captures sludge, rust particles, and other dirt that could damage the heat exchanger in the heat pump. A typical cleaning interval is once a year, and in a new system (first year of operation), it may even be twice.

Cleaning procedure:

Close the ball valves before and after the filter.
Depressurize the filter – most have a small air vent or you open it slowly to let the pressure escape gradually.
Remove the filter insert, rinse it under running water, or clean it with a sponge.
Check the sealing ring and replace it if there are signs of damage.
Reassemble, open the valves, and check for tightness.

Deairing the hydraulic circuit

Air bubbles in the circuit are the silent enemy of every heat pump. They cause characteristic "gurgling" or "clicking" in the pipes, reduce flow, and in extreme cases can cause cavitation in the circulation pump. Deairing is a task that anyone can do, as long as they know where the air vents are.

You will need for deairing:

Deairing key (small square or hexagonal, usually 5 mm)
Container to catch water droplets
Cloth

Turn the thermostat to a higher temperature so the circulation pump runs. Open the air vents on the radiators or in the floor heating manifold one after another, until only water flows out without air bubbles. Note: in a heat pump system, the hydraulic circuit is under pressure typically 1.5–2.5 bar, so water can "shoot out" – have a cloth and container ready.

After deairing, check the pressure in the system on the pressure gauge. If the pressure drops below the minimum value (typically 1 bar), refill the system with water via the filling point. If you cannot reach or the pressure drops quickly again, the expansion tank is likely damaged or there is a leak somewhere – this is a case for a professional.

Checking and setting the control unit

The control unit of a heat pump is in modern units a full-fledged computer with a touch screen, web interface, or mobile app. Setting parameters is a self-service task – no certificates or professional training are needed for this. It is, however, necessary to understand what you are setting.

The most common settings that every heat pump owner should know:

Heating curve: The dependence of water temperature on outdoor temperature. Too steep a curve = unnecessarily high temperatures and low COP. Too flat a curve = a cold house in the cold. Proper setting takes several weeks of experimenting.
Throttling setting: At night or when leaving the house, it is reasonable to reduce the temperature by 2–4 °C, not more. Heat pumps are more efficient with even operation than with repeated large heating cycles.
Hot water priority: If you have a hot water storage tank, set when it should be heated – typically before waking up in the morning or during the day when the outdoor temperature is higher.
Bivalent point: The temperature at which the bivalent source (electric heating element, boiler) is activated. A bivalent point set too high means unnecessarily expensive electric heating.

Checking and replacing the self-regulating heating cable

In air-to-water heat pumps, condensate accumulates in the drip tray under the evaporator. In winter, freezing of this condensate can damage the tray and impair defrosting. Protection is provided by a self-regulating heating cable for TČ range ITEC, which is placed directly into the tray.

The self-regulating cable is an intelligent solution – its power automatically increases when the temperature drops, and vice versa. It does not require a thermostat. Checking this cable is simple:

Visually check that the cable insulation is not damaged.
Check that the cable is still properly placed in the tray and does not exceed the edge.
By touch or with a non-contact thermometer, verify that it heats up when turned on.
The lifespan of a self-regulating cable is 8–12 years – after this period, I recommend replacing it preventively.

Installation and checking of accessories

Modern heat pumps are designed with an open architecture for accessories – manufacturers expect that customers will purchase additional components. For example, a hot water circulation set for ITEC-T, ATHENA-T, LEGEND, CALIBRA and ATLAS can be installed by oneself – the set includes all necessary components including a circulation pump, a programmable switching module, and necessary valves.

Similarly, connection kit for TČ range CALIBRA DUO and ATLAS DUO is typically customer-installable accessory – it is a hydraulic connection that does not require interference with the refrigerant circuit. Basic plumbing experience and proper tightening according to the specified torque are sufficient.

If you need to expand the control options of the heat pump – for example, to connect a mixed circuit, an external tank, or a smart home system – an expansion module for ITEC heat pumps allows adding further control inputs and outputs. The actual wiring of the module is manageable by technically capable owners, but I recommend studying the relevant documentation and the article Expansion module for heat pumps – when and why you need it from our Knowledge Center.

A special category of accessories is a relay kit for Diplomat Optimum G3 heat pumps, which converts a 3–10 V signal into a simple on/off output for a mixed circuit pump. This is an electronic accessory whose physical installation (plugging into the distribution board) is relatively simple, but I recommend having it wired by a professional if you do not have experience with electrical installation.

What a layperson MUST NOT do – and why

Refrigerant circuit: absolutely forbidden areas

Refrigerant R32 (most commonly used in modern heat pumps) is flammable (class A2L), R410A is non-flammable but has an enormous GWP (Global Warming Potential) – 2 088 compared to CO₂. Work with refrigerants requires not only a certificate according to the F-gas regulation, but also specific equipment: filling scales, refrigerant analyzer, vacuum pump, and manometer stations.

If the heat pump is losing performance, if the compressor is running but not heating, if you see frost on the refrigerant piping in places where it shouldn't be – these are signs of a refrigerant leak or a problem in the refrigerant circuit. Do not open the service valves of the refrigerant circuit and do not call a "heater guy" – call a certified F-gas technician.

Electrical installation and switchboard

Heat pumps are powered by three-phase power supply (3×400 V), with the compressor's starting current reaching 50–80 A. Any work on the heat pump's electrical switchboard should be done exclusively by a qualified electrician. This applies even to seemingly simple tasks such as replacing fuses or contactors – incorrect procedures can result in electric shock, fire, or damage to the control electronics.

Primary ground-water system circuit
Ground collectors or boreholes are filled with a glycol mixture (typically propylene glycol 30–40 %) under pressure. This circuit is entirely underground and its repair is extremely costly (excavation work). Any interventions in this circuit – topping up glycol, pressure check, leak detection – should be carried out exclusively by specialized companies with professional equipment for leak detection.

Diagnosis of common problems: what you can see yourself before the technician arrives

When a customer calls and says the "heat pump is not working," the first thing I ask is: "What exactly is happening and what do you see on the display?" Most modern heat pumps have extensive diagnostics and error codes. Before calling a service company, note down:

Error code – write it down exactly, or take a photo of the display.
Current temperatures – outside temperature, system water temperature, DHW tank temperature.
Power consumption – if you have a power meter on the heat pump, record the value in watts.
Noises – describe any unusual sounds (clicking, whistling, vibrations).
When it occurred – during what weather, after what event (power outage, storm, frost).

This information dramatically shortens the diagnostic time and in some cases the technician can resolve the issue remotely (e.g., remote reset, parameter change).

For more information on common faults and how to recognize them, read the article Common heat pump faults and how to recognize them directly in our Knowledge Center.

Service contracts: are they worth it?

A service contract with an authorized service partner is an investment that pays off for most heat pump owners. Not primarily because annual service is particularly expensive (depending on the region and the heat pump's capacity, it ranges between 100–250 € excluding spare parts), but because:

You have a documented service history – essential for warranty claims.
The technician knows your specific system and reacts faster in case of problems.
Problems detected preventively (weakening compressor, developing refrigerant leak) are several times cheaper than emergency repairs in the middle of winter.
Some manufacturers extend the warranty when proof of regular service by an authorized company is provided.

A typical service contract includes an annual inspection, priority service in case of a breakdown, and a discount on spare parts. It is not necessary to have it directly from the seller – an authorized service partner of the manufacturer is sufficient.

Lifespan of components: what and when to replace

A heat pump as a whole has a lifespan of 20–25 years with proper maintenance. Individual components, however, have different lifespans and their timely replacement extends the life of the entire system.

Component	Typical lifespan	Note
Compressor	15–20 years	Depends on number of starts and refrigerant quality
Circulation pump	10–15 years	Sooner with dirty water
Expansion tank	8–12 years	Membrane ages, check gas pressure annually
Self-regulating cable	8–12 years	Replace preventively before the end of its lifespan
Filter screen	permanent (clean annually)	Replace only in case of damage
Electronic control unit	12–18 years	Sensitive to surge protectors
Anode in DHW tank	3–5 years	Critical for tank protection against corrosion

I would like to draw special attention to the magnesium or titanium anode in the TUV tank. This is a component that is often overlooked, yet it is crucial – without a functioning anode, the steel tank of the boiler will start to corrode. Replacing the anode is a simple and inexpensive task (anode price 15–30 €, work 30 minutes), but if neglected, the result can be tank corrosion costing thousands of euros.

Winter problems: defrosting, frost buildup and what to do about it

One of the most common questions from owners of air-to-water heat pumps is: "Is it normal for the outdoor unit to be completely covered in ice?" The answer is: it depends on the situation.

Modern air-to-water heat pumps have a built-in defrost cycle. When the outside temperature drops below 0 °C and the air humidity is high, frost forms on the evaporator. This is physically inevitable. The control unit periodically (typically every 45–90 minutes) initiates a defrost cycle – it reverses the refrigerant cycle, heats the evaporator, and melts the ice. During this cycle, steam is visible coming from the outdoor unit and the heating system temperature drops – this is normal.

Abnormal situations include:

If the unit is still frozen after prolonged operation at temperatures above +5 °C.
If the defrost cycle lasts too long (more than 15–20 minutes) or does not start at all.
If ice is growing on the sides or on the compressor (not just on the evaporator).
If the drain tray is blocked by ice – indicating a faulty heating cable in the tray.

These situations are symptoms of a faulty defrost system, a faulty outdoor temperature sensor, or refrigerant shortage – and they require service intervention.

Overvoltage protection and power outages: how the heat pump handles it

Heat pumps are relatively sensitive to overvoltage and sudden power outages and restarts. After a power outage, the compressor must not restart immediately – it needs time to equalize pressures in the refrigerant circuit. Modern heat pumps handle this automatically using a built-in delay (typically 3–5 minutes after power is restored).

If you live in an area with frequent power outages, I recommend:

Installing overvoltage protection (SPD – Surge Protective Device) directly in the heat pump's distribution panel.
Considering a UPS (uninterruptible power supply) at least for the control electronics – not for the compressor (which is too powerful), but to ensure the control unit survives short outages without losing settings.
After each longer power outage, check whether the heat pump starts up correctly and whether there is no error code on the display.

Documentation and records: keeping a service log

This is an aspect that most customers underestimate, and it later causes problems during warranty claims or when selling property. I recommend keeping a simple service log – a notebook or an Excel table is sufficient.

The service log should include:

Date and description of each service intervention (including self-service actions).
Notes from the service technician (measurement results, refrigerant top-up, replaced parts).
Error codes with the date and circumstances of occurrence.
Electricity consumption per heating season (enables trend tracking).
Changes in the control unit settings (what, when, and why you changed it).

You will appreciate this log yourself – when you return to a problem you solved three years ago, you will be able to precisely recall what happened at that time.

Frequently asked questions (FAQ)

How often should a heat pump be serviced?

At least once a year by a certified service technician. Self-service tasks (cleaning the evaporator, bleeding air, checking the filter) are recommended twice a year – in spring and autumn. In the first year of operation, it is advisable to check the filter after 3 months as well, since a new system has a higher level of impurities from installation.

Can I refill the refrigerant myself if it seems to be running low?

No. Work with refrigerants requires a certificate under the EU regulation on F-gases (F-gas certificate). In addition to the legal aspect, there is also a practical one – without the proper equipment (vacuum pump, manifold gauge set, precise scales), it is not possible to refill the refrigerant correctly. Moreover, a drop in refrigerant always indicates a leak – refilling without fixing the leak is only a temporary solution.

What should I do if the heat pump displays an error code and shuts down?

Note the exact code (take a photo of the display), record the outside temperature and the circumstances. Try a manual reset according to the instructions (usually a long button press or turning off and on via the control unit). If the heat pump restarts and runs normally, monitor it and note whether the code recurs – and if so, under what conditions. If the heat pump does not restart or the code recurs within an hour, contact service. Never use emergency electric heating as a permanent solution – electricity is 3–4 times more expensive than a heat pump.

Is it normal to hear the heat pump from outside or inside?

The outdoor unit produces noise – the fan and compressor are noise sources with a typical level of 45–60 dB(A) at a distance of 1 m. Inside, you should only hear the quiet hum of the circulation pump in the pipes. Abnormal sounds include: metallic clicking (may indicate air in the system or a damaged compressor), squeaking or squealing (fan bearings), strong vibrations (loose compressor mounting). Bubbling in the pipes typically indicates air – bleed the system.

Can I replace the circulation pump in the hydraulic circuit myself?

Technically yes – a circulation pump is a hydraulic component and its replacement does not require working with refrigerant. It is similar to replacing a pump in central heating. You need to close the circuit, drain it, replace the pump (watch the flow direction!), and refill and bleed it again. If you have no experience with hydraulics, I recommend leaving it to a plumber – the risk lies mainly in incorrect installation direction or a leaky connection, not in the pump itself.

What is the lifespan of a heat pump and when is it worth replacing rather than repairing?

With proper maintenance, the lifespan is 20–25 years. A general rule of thumb for deciding between repair and replacement: if the repair costs exceed 30–40% of the value of a new unit and the device is more than 12–15 years old, consider replacement. New heat pumps have significantly higher COP and lower consumption – the electricity savings can compensate for the price difference in 5–8 years. At the same time, modern units operate with low-GWP refrigerants that have a smaller impact on climate change.

Conclusion: Preventive care always pays off

A heat pump is an exceptionally reliable technology – but only if it is regularly maintained. From experience, I know that the most expensive repairs (compressors, heat exchangers, electronics) usually arise not from manufacturing defects, but from neglecting basic tasks: a dirty evaporator, contaminated water in the circuit, ignored warning codes. These issues can be detected by an annual inspection or even by a simple visual check.

DIY maintenance has its clear logic: do what is safe, reversible, and for which you have the equipment. Leave everything else to certified professionals – not only for warranty reasons, but also because a qualified technician with diagnostic equipment can detect problems before they turn into failures.

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