6 common mistakes when designing heat pumps
%25203%2520(1).webp)
Stefano Fonseca is an energy and environment engineer with over six years of experience in technical building equipment (TGA). He combines technical expertise with a passion for understandable communication. For more than five years, he has been writing as a freelance editor about renewable energy and sustainable living, in particular about photovoltaics and heat pumps.
Despite high expectations, the success of some heat pumps falls short of opportunities. This is often not due to the technology itself, but to planning errors, which are only noticeable after installation. In this article, you will find out why every detail is important when interpreting — and what common mistakes this entails.
Typical errors when designing heat pumps
Many heat pumps work inefficiently or cause high costs because they are incorrectly dimensioned, poorly planned or do not fit the heating system. The following table shows the most common errors of interpretation, their consequences and possible solutions:
1. Wrong sizing
A heat pump that is too large switches on and off constantly (cycles), which leads to increased wear, loud noises and unnecessarily high electricity costs. On the other hand, a heat pump that is too small will not be able to adequately heat the building when the outside temperatures are low — a problem, especially in old buildings. This lowers living comfort and can even lead to frost damage.
The exact heat load of the building must be DIN EN 12831 calculated become. This is the only way to determine the correct output of the heat pump. Rules of thumb per square meter are not enough. It must also be checked whether a monovalent or bivalent operation is planned.
2. No or incorrect heating load calculation
Anyone who selects the heat pump “based on feeling” or only on the basis of living space risks a completely wrong design. The result is high operating costs, uneven heat distribution, no access to subsidies or even damage to the system.
Die Heat load calculation should always be done individually and in accordance with standards. For this purpose, among others, the U-values of the building envelope, which takes ventilation heat loss, temperature differences and geographical location into account. Reputable specialist companies offer this service as standard.
3. Unsuitable heat source
If the selected heat source is not suitable for the location or building standard, efficiency drops drastically. A geothermal probe that is too short can freeze if the extraction capacity is high. An air-water heat pump may not provide enough energy in severe frost — this requires the use of a heating rod (additional heating) and increases electricity consumption.
The choice of heat source should be based on the location, available space and the desired temperature level. For geothermal energy, probe length and soil conditions must be taken into account. For air-water heat pumps, the annual performance factor (JAZ) is decisive in the cold season.
4. Wrong heating system
If the heating system is not designed for low flow temperatures (e.g. old radiators), the heat pump cannot operate efficiently. Power consumption increases and the heat pump runs at full load, which shortens the lifespan. In addition, the house may not be warm enough.
Low-temperature systems such as panel heating (floor, wall or ceiling heating) are ideal. If radiators persist, they must be checked and, if necessary, replaced with larger variants. An adjustment of the hydraulic system is usually necessary.
5. Lack of hydraulic balance
Ohne hydraulic balancing are individual heating surfaces oversupplied or undersupplied. This results in inefficient operation, uneven room temperature and increased power consumption due to the circulation pump. The heat pump is not running optimally and consumes more energy than necessary.
Hydraulic balancing ensures that each radiator or heating circuit receives exactly the amount of heat it needs. It is essential for efficient operation of the heat pump and is also required by funding programs such as the BEG.
6. Incorrectly designed or unnecessary buffer tank
A too large or incorrectly integrated buffer tank causes additional heat losses and extends the running times of the heat pump. This lowers efficiency, increases energy consumption and makes the system slower. The clocking can also be increased as a result.
A Buffer tank should only be installed thenwhen it is technically necessary — e.g. for multi-circuit systems or for hydraulic decoupling. The connection must be precisely tailored to the operating mode of the heat pump. In many cases, a small memory is sufficient or is even completely superfluous.
What are the consequences of an incorrect interpretation?
An incorrectly designed heat pump not only causes higher operating costs, but can also impair living comfort and shorten the life of the system. An overview of the most common consequences:
- High power consumption due to inefficient operation
- Frequent clockingthat causes wear and noise
- Inadequate heating capacity on cold days
- Low living comfort due to uneven temperatures
- Shortened lifespan the heat pump
- Issues with funding, e.g. recoveries in the event of deviations from planning
- Difficult maintenance or retrofitting in case of faulty system design
- Loud operation, especially with oversized air heat pumps
How can you recognize an incorrectly designed heat pump?
An incorrectly designed heat pump usually only appears during operation — due to unusual noises, high electricity costs or a lack of heating capacity. Typical signs include:
- Frequent clocking (continuous switching on and off)
- Significantly higher electricity costs as expected
- Inadequate heat output in case of frost or in individual rooms
- Irregular room temperatures despite thermostat control
- Continuous operation of the heating rod for air-water heat pumps
- Volume issues, especially in outdoor units
- Condensate problems or icing on the outdoor unit
Checklist: Buying a heat pump
With this checklist, you can ensure that nothing is forgotten when choosing and installing your heat pump. Just print it out and check it off point by point:
How do I find a good specialist company?
A good specialist company is crucial for the correct design and efficient operation of your heat pump. When choosing, pay attention to the following criteria:
- Heat load calculation is offered: A reputable company calculates the heat load in accordance with DIN EN 12831 and does not plan “based on feeling”.
- Experience with heat pumps: Ask for references or sample projects, ideally for similar types of buildings.
- Certifications and qualifications: Look for certificates such as “heat pump specialist partners” or training from manufacturers.
- Transparent offers: All services, costs and components should be clearly stated in the offer.
- Advice on eligibility: A good company is familiar with the current funding programs and helps with the application process.
- Technically sophisticated concept: Not only is the heat pump offered, but an entire system including hydraulics, buffer tank and heating surfaces is tested.
- Accessibility and service: Clarify in advance how the company can be reached in the event of questions, maintenance or faults.
Tip: Get several offers and compare not only the price, but also the professional quality and advice. A good preliminary discussion is often the best indication of professional competence.
autarc: Your partner for efficient planning of heat pumps — find out more now!
Rely on quality and expertise when planning and installing heat pump systems. With our Heat pump check receive comprehensive support so that you can implement your projects efficiently and sustainably. Contact us today and benefit from our expert knowledge!