How to choose a DAB circulation pump for heating
How to choose a DAB circulation pump for heating – complete guide
Selecting a circulation pump is one of those decisions that most people underestimate – until their old pump fails in the middle of a January freeze or until they get a shock from their annual electricity bill. A well-chosen DAB pump ensures that your heating system operates efficiently, quietly, and with minimal consumption. A poorly chosen one will unnecessarily drain money from your wallet each month or will not be able to circulate the heating system sufficiently.
This article will give you everything you need to know before choosing a specific model. We will go through the basic parameters, differences between model ranges, practical scenarios from everyday households, and tips on what to watch out for during installation. If you are looking for a comparison of specific models, also see the article DAB EVOTRON vs EVOSTA2 – which pump to choose in our Knowledge Center.
Why is the selection of a pump so important?
A circulation pump is the heart of every heating system. Without it, hot water from the boiler would simply not flow to the radiators – or it would flow very slowly and unevenly. In practice, this means that some rooms would be overheated, others cold, and the boiler would operate inefficiently.
The pump operates 24 hours a day, 7 days a week, usually for the entire heating season – sometimes even year-round in systems with hot water. This means that its annual electricity consumption can be as high as 300–500 kWh per year in older models. Modern pumps of energy class A (such as the DAB EVOSTA2 or EVOTRON range) consume only 5–15% of this value – that is 20–60 kWh per year. The difference on the electricity bill can easily be 60–100 € per year in favor of the new pump. Therefore, replacing an old pump usually pays for itself within 2–4 years.
Energy efficiency is not the only consideration – hydraulic correctness is also important: a too weak pump will not circulate the entire system, while a too strong one causes noise, hydraulic shock, and premature wear of thermostatic valves. The correct choice is therefore a compromise between sufficient performance and the lowest possible consumption.
Basic parameters you need to know
Before you choose a specific model, you need to know a few values. Some you can find out yourself, others you will need a project or the help of a technician.
Flow rate (Q) – how much water the pump must move
Flow rate is expressed in cubic meters per hour (m³/h) or liters per minute (l/min). It depends on the power of your heating system and the temperature difference between the supply and return. For a typical family home with a temperature drop of 80/60 °C (delta T = 20 K), the approximate formula is:
Q (m³/h) = system power (kW) / (1.16 × delta T)
Example: Boiler 20 kW, delta T = 20 K → Q = 20 / (1.16 × 20) = 20 / 23.2 ≈ 0.86 m³/h
For modern low-temperature systems (floor heating, heat pumps), the delta T is smaller – typically 5–10 K – and the flow rate must therefore be significantly higher for the same boiler power. This is important to consider when choosing a pump.
Head (H) – the pressure the pump must overcome
Head (hydraulic resistance of the system) is expressed in meters of water column (m). It depends on the length and diameter of the pipes, the number and setting of thermostatic valves, flow resistances of collectors, valves and fittings. For simple home systems, it ranges from 1–4 m, for more extensive or hydraulically demanding systems from 4–8 m.
An exact calculation requires a hydraulic project. In practice, however, most technicians recommend a pump with a maximum head of 4–6 m for typical family homes (up to 150 m²), which covers the vast majority of situations.
Mounting length and connection
Heating pumps are manufactured in standard mounting lengths: 130 mm and 180 mm are the most common. The diameter of the threaded connection is usually 1" or 1½" (G1 or G1½). Always measure the space you have available and the thread of the existing flanges before purchasing – this will help you avoid unnecessary returns or improvised adapters.
Sets with unions, such as the KIT with union DAB.EVOSTA2 40-70/180, include everything needed for direct installation and save you the hassle of searching for compatible fittings separately.
Maximum medium temperature
Standard circulation pumps for heating are designed for a maximum of 110–120 °C. In practice, most boilers operate at 70–85 °C, so this is usually not an issue. However, be cautious with certain special applications (solar collectors, high-temperature condensing boilers) – always check the pump's technical data sheet.
DAB model series for heating – overview and differences
The brand DAB offers several product lines for the heating and plumbing sectors. For typical single-family homes, the following models are primarily suitable:
DAB EVOSTA2 – electronically controlled pump of class A
EVOSTA2 is DAB's flagship product for residential heating. It is a smart pump with electronically controlled rotational speed that automatically adapts to the current needs of the system. It features an integrated frequency inverter and a microprocessor that continuously evaluates hydraulic resistance and adjusts performance.
Key features of the EVOSTA2 model:
- Energy class A – consumption typically 3–45 W depending on the operating point
- Automatic mode (Δp-v, Δp-c, constant speed) – you choose according to the type of system
- Integrated air vent – helps during the first start-up and during regular operation
- Display showing performance, flow rate and operating hours
- Construction length 180 mm (model 40-70/180) or 130 mm
- Flow range 0.5–3.5 m³/h, head 0.5–7.0 m
- Maximum medium temperature 110 °C
- Quiet operation – in a quiet house it is inaudible
In most cases, EVOSTA2 is the best choice for both modern and older single-family homes. It pays for itself in energy savings within 3 years and lasts 10–15 years without maintenance under normal operation. In addition to the basic version, we also offer the KIT with union DAB.EVOSTA2 40-70/180 with FILTERBALL filter, which includes a magnetic filter for impurities – particularly useful in older systems.
For the case of a power outage, we also offer the KIT DAB.EVOSTA2 40-70/180 with backup power supply, which ensures that the heating will continue to function during a blackout. More on this topic can be found in the article Backup power supply for DAB pump – when and why to use it.
DAB EVOTRON – energy-saving pump for simple applications
EVOTRON is an entry-level electronically controlled pump. Compared to EVOSTA2, it has a simpler control algorithm and fewer adjustment options, but it is still an energy class A pump with significantly lower consumption than old circulation pumps. It is suitable for smaller systems, apartment units, or where advanced automation is not needed.
The model DAB.EVOTRON 40/130 with a construction length of 130 mm covers smaller to medium systems and is more cost-effective. If you are deciding between EVOTRON and EVOSTA2, please read the comparison article DAB EVOTRON vs EVOSTA2 – which pump to choose.
DAB VA – traditional three-speed pumps
The VA series (for example, DAB VA35/130) represents classic circulation pumps with a manual three-speed switch. They do not have electronic control, so they always run at set speeds regardless of the system's current needs. Their advantage is simplicity, robustness, and lower purchase price. The disadvantage is higher electricity consumption – they belong to energy class C or D.
VA pumps are suitable for older apartment blocks, cottages, houses where there is no requirement for energy saving, or as a replacement solution in case of failure. In new installations, we recommend preferring EVOSTA2 or EVOTRON for long-term operational economy.
How to correctly dimension a pump – practical examples
Theory is one thing, but in practice we encounter specific houses and specific situations. Here are a few scenarios that we encounter most often:
Scenario 1: Single-family house 120 m², boiler 18 kW, 8 radiators
This is probably the most common case. A house from the 70s–80s, original cast iron or steel radiators, boiler replaced with a condensing one. Temperature difference is usually 75/55 °C (delta T = 20 K). Flow calculation: Q = 18 / (1.16 × 20) = 0.78 m³/h. Hydraulic resistance of the system with 8 radiators and thermostatic valves is estimated at 2–4 m. Recommendation: DAB EVOSTA2 40-70/180 – it more than covers the requirements, and in addition it has automatic control, so it adapts to different conditions (closed thermostatic valves, night setback, etc.). One year of operation = approx. 30–40 kWh, which is 4–6 € in electricity costs.
Scenario 2: Apartment in a panel building, apartment delivery station, 3 radiators
In an apartment building, each apartment has its own small pump for the apartment loop. The system is short, resistance is low (1–2 m), flow is small (up to 0.5 m³/h). A compact model with a construction length of 130 mm is sufficient here – for example, DAB EVOTRON 40/130. A full EVOSTA2 would be oversized and unnecessarily expensive here.
Scenario 3: Floor heating, heat pump, low-temperature system
Floor heating operates at temperatures of 35/28 °C (delta T = 7 K) and requires a much higher flow than a radiator system with the same boiler output. For a 10 kW heat pump: Q = 10 / (1.16 × 7) = 1.23 m³/h. Hydraulic resistance of distributors and floor loops can be 4–7 m. Recommendation: EVOSTA2 again, but it is essential to verify that the selected model can handle the combination of higher flow and sufficient head. It is important to set the pump to Δp-v (proportional pressure) mode, where it automatically increases flow when needed.
Scenario 4: Replacing an old pump due to failure
This is the case when you need to replace a pump quickly and the house is without heating. In this case, it pays off to have a pump with unions as a ready-made set – you can replace it in 20–30 minutes without any pipe modifications. DAB kits with unions are made exactly for this purpose. The replacement procedure is described in detail in the article Installation of DAB circulation pump step by step.
Additional functions and accessories – what is worth it?
Sludge filter (Filterball)
In heating systems, magnetic sludge – small particles of corrosion from iron pipes and radiators – accumulates over time. This sludge settles on the pump rotor, clogs thermostatic valves, and causes reduced performance, noise, and premature wear. A magnetic filter (Filterball) captures these impurities before they reach the pump.
If you have an older system (15+ years, steel or cast iron radiators), investing in a set with a filter is definitely justified. The DAB.EVOSTA2 set with the FILTERBALL filter is an ideal solution for such systems. For more information on this topic, see the article DAB pump with or without a filter – does the Filterball set pay off?.
Backup power supply
In the event of a power outage, the boiler and pump will stop. In harsh winters, this can mean frozen pipes – especially in cottages or during longer blackouts. A backup power source (UPS for the pump) keeps the pump running for several hours even without electricity. This investment makes sense mainly in areas with an unstable grid or in new buildings with heat pumps, where an outage can be more costly. See the article Backup power supply for DAB pump – when and why to use it.
Mounting unions and reducers
If you are buying just the pump without a set, don't forget to check what thread your pipe has. Most DAB pumps have a G1½" external thread connection. If your pipe is G1" or ¾", you will need reducers. It is much easier to buy a complete set with unions – they are cheaper than you might think, and you will save time and nerves.
What to pay attention to when choosing – common mistakes
Over the years of selling heating technology, we have seen several mistakes that repeat themselves again and again. You can avoid them if you read the following lines:
1. Buying a pump without knowing the built-in length. The most common reason for returning goods. An old ceiling between unions is 130 mm, the new pump is 180 mm – and there is a problem. Always measure the distance between the centers of the unions (center-to-center) before ordering.
2. Oversizing "just to be safe". A larger pump does not mean better heating. On the contrary – it causes excessive pressure, noise in the valves (characteristic hissing sound), and shortens the life of the fittings. Electronically controlled pumps (EVOSTA2, EVOTRON) can adjust themselves, but a significant overperformance is still not ideal.
3. Ignoring the energy class. Pumps of classes C and D are still being sold – and customers buy them because they are cheaper. After 3 years, they regret it. We recommend class A only. More in the article Energy class A DAB pumps – what it means and why it pays off.
4. Installation without bleeding the system. After replacing the pump, you must bleed the entire system, otherwise air will get trapped in the radiators and the pump will work with air instead of water – knocking sounds, weak performance. EVOSTA2 pumps have a built-in bleeding mechanism, but manual bleeding of the radiators is still necessary.
5. Neglecting the flow direction. The pump has a specified flow direction (arrow on the pump body). If you install it backwards, it will work incorrectly. At the same time – the pump should be installed in the return (cold side), not in the supply, to protect the bearings and electronics from high temperatures.
6. Forgetting the shut-off valves. Without ball valves on both sides of the pump, you will have to drain the entire system when replacing the pump. With valves, you can do it in 15 minutes without losing water. DAB sets with unions usually include shut-off options.
A detailed step-by-step guide to correct installation can be found in the article Installation of a DAB circulation pump step by step. Read about the most common faults and their solutions in the article Common faults of DAB circulation pumps and their solutions.
Setting up the pump after installation
Modern electronic DAB pumps offer several operating modes. Correct setup has a big impact on efficiency and comfort:
Δp-v mode (variable differential pressure): The pump adjusts its speed to maintain a differential pressure that increases with flow. Ideal for radiator systems with thermostatic valves – when the valves close, the pump slows down. This is the recommended mode for most standard installations.
Δp-c mode (constant differential pressure): The pump maintains a constant pressure regardless of flow. Suitable for systems with low resistance or for floor heating where valves do not change resistance as dramatically.
Constant speed (1/2/3): A classic manual mode where you choose the speed yourself. Suitable only for simple systems without thermostatic valves, where the hydraulics do not change. With thermostats, it causes noise and energy waste.
At first start-up, we recommend setting the EVOSTA2 to automatic Δp-v mode and letting it run for 24 hours. The pump will "learn" the system and set optimal parameters by itself. After that, you can fine-tune it as needed.
Lifespan and maintenance of DAB pumps
Properly installed and maintained DAB pump should last 10–15 years without major intervention. The main factors that affect lifespan:
- Water quality in the system – hard water with high mineral content creates limescale on the rotor. We recommend adding softened water to the system or adding a corrosion inhibitor.
- Presence of sludge – magnetic sludge destroys bearings and the motor. The Filterball filter dramatically extends the life of the pump.
- Proper installation – the pump must be installed horizontally (shaft horizontal), not at an angle or vertically, unless the manufacturer explicitly allows it.
- Summer shutdown – if the pump stands idle all summer, the rotor can become blocked by lime deposits. Manually turn it once a month or set it to run for a short daily period.
Read more about caring for your pump in the article Cleaning and maintenance of DAB pump – how to extend its lifespan.
Price vs. return on investment – calculation for a real house
Let's compare the costs of 10 years of operation for three types of pumps in a typical family home (boiler 20 kW, electricity price 0.22 €/kWh):
| Model | Purchase price | Annual consumption | Costs/year (electricity) | Total costs 10 years |
|---|---|---|---|---|
| Old VA pump | ~60 € | 350 kWh | 77 € | 830 € |
| DAB EVOTRON | ~120 € | 90 kWh | 20 € | 320 € |
| DAB EVOSTA2 | ~180 € | 35 kWh | 7,7 € | 257 € |
The difference between an old VA pump and the modern EVOSTA2 is over 570 € in 10 years – just on electricity. Meanwhile, the EVOSTA2 is 120 € more expensive to buy. Net savings: over 450 €. And that's just one pump, at today's electricity prices – in a few years, the difference could be even more significant.
Most frequently asked questions (FAQ)
How do I determine what pump power I need for my home?
The basic calculation is based on the boiler power and the system temperature difference. For a typical family home with a 15–25 kW boiler and a radiator system, a pump with a maximum flow of 2.5–3.5 m³/h and a maximum head of 4–6 m is sufficient – which is covered, for example, by the EVOSTA2 40-70/180. A more detailed calculation procedure can be found in the article What pump power of DAB do I need for my home. If you are unsure, contact us – we will help you choose based on your specific parameters.
Can I replace the pump myself, without a plumber?
If you have shut-off valves before and after the pump, the replacement is relatively simple and can be done by a skilled DIY enthusiast. The procedure includes: closing the valves, unscrewing the flanges, replacing the gaskets, mounting the new pump (correct direction!), and bleeding the system. Without valves, you have to drain the entire system – which is more complicated and we recommend a professional. See our detailed step-by-step guide in the article Installation of DAB circulation pump step by step.
The pump makes noise after replacement – why?
The most common cause is air in the system. Bleed all radiators and check the pressure in the expansion tank (it should be 1.0–1.5 bar in a cold system). Another possibility: the pump is running at too high a speed or in an unsuitable mode – switch to automatic Δp-v. If the noise persists, it may be a bearing failure or a blocked rotor. Details in the article Common DAB circulation pump faults and their solutions.
Is it worth buying a set with flanges instead of just the pump?
Yes, in most cases. Sets include flanges with ball valves, which save you from having to look for compatible parts separately and potential sealing problems in case of a damaged thread. The price difference compared to the pump alone is minimal (about 15–25 €), while the added value is significant. This is especially true for renovations, where we cannot know in advance exactly what thread is on the pipe.
What is the difference between Δp-v and Δp-c mode?
In Δp-v (variable pressure) mode, the pump reduces pressure proportionally to the flow – when thermostatic valves close, the pump slows down and saves energy. In Δp-c mode, the pump maintains the same differential pressure regardless of the flow. For standard radiator systems with thermostats, we recommend Δp-v – it is more economical and quieter. For long circuits without thermostats or floor heating with a single manifold, Δp-c may be more suitable.
How long will the DAB EVOSTA2 pump last?
With proper installation, clean water in the system, and a magnetic filter for impurities, you can realistically expect 12–15 years of trouble-free operation. The manufacturer guarantees the lifespan of components for 20,000 operating hours, which at continuous year-round operation is about 8–9 years, and at seasonal operation (8 months) more than 10 years. The warranty period according to Slovak law is 24 months.
Conclusion – what to take away from this article
Selecting the right DAB circulation pump does not have to be done blindly. Three key things are important: knowing the boiler power and system type, measuring the construction length and pipe thread diameter of the existing installation, and deciding on an energy-efficient class A – which in practice means EVOSTA2 or EVOTRON depending on the size of the house.
For the vast majority of family homes in Slovakia, the KIT with flange DAB.EVOSTA2 40-70/180 is the right choice – it covers boiler power from 10 to 30 kW, has automatic regulation, an integrated air vent, and a display. It is a pump that you install and forget about for the next decade.
If you have an older system with sludge, go for the version with the FILTERBALL filter. If you live in an area with unstable electricity or want to be sure in case of a power outage, consider a set with a backup power supply. And if you have a smaller system or an apartment installation, take a look at DAB EVOTRON 40/130 as a more cost-effective and energy-saving alternative.
Further questions and answers can also be found in the Common questions about DAB pumps section in our Knowledge Center.
Do you have a question on this topic?
Having trouble making a decision or dealing with a specific situation in your home? Write to us – we'll be happy to help.