Backup power supply for DAB pump – when and why to use it
Standby power supply for DAB pump – when and why to use it
The circulation pump is the heart of every heating system. As long as it runs, you won't even notice it – the quiet, reliable movement of the heat transfer fluid through radiators, floor heating loops or hot water storage tanks. But what happens if a power outage stops the pump in the middle of a freezing January night? Or if a storm interrupts the power supply for several hours exactly when the house is full of people and it's freezing outside? That's when the backup power supply – UPS (Uninterruptible Power Supply) or another backup system – comes into play and its value becomes fully apparent.
In this article, we will explain in detail what a backup power supply for a circulation pump actually is, how it works, in which situations it is really worth it, and what to consider when choosing the right solution. We will also look at specific products from the DAB portfolio that can be combined with a backup system, and we will tell you what to pay attention to during installation.
What is a backup power supply and how does it work in the context of heating
A backup power supply (UPS – Uninterruptible Power Supply) is a device that, in the event of a power grid failure, immediately and without interruption switches the powered device to its own battery. Unlike a conventional backup generator, there is no interruption in power supply – the switch takes less than a millisecond, so the pump's electronics will not register any change at all.
In practice, this works as follows: the UPS is permanently connected between the power outlet and the pump. As long as the grid is working, the UPS powers the pump from the grid and at the same time keeps the battery charged. When the voltage in the grid drops or completely fails, the UPS immediately switches to the battery and the pump continues to operate without any interruption. After the grid voltage is restored, the UPS switches back silently and starts charging the battery.
For a circulation pump, this immediate switching is crucial – modern electronic pumps with control electronics (such as DAB EVOSTA2 or EVOTRON pumps) have sensitive circuits that may register an error or require manual restart in the event of a sudden power failure and subsequent reconnection. The UPS prevents this scenario.
When a power outage really harms the heating system
Not every power outage is equally dangerous. It depends on what type of heating system you have, what the outside temperature is, and how long the power interruption lasts. Let's look at specific scenarios in which a pump failure can cause real problems.
Condensing boiler – complete dependence on electricity
Modern condensing boilers are fully electrically dependent – in addition to the pump, they need electricity for the control electronics, ignition, exhaust fan and modulating gas valve. In the event of a power outage, the boiler turns off. This in itself is not a catastrophe, but if the outage lasts longer, the boiler goes through a startup sequence when it is turned on again, which can take several minutes. In the meantime, there is no heat in the system. A backup power supply for the pump alone is not enough here – but it can prevent the system from cooling down so much that it will need a longer time to reach a comfortable temperature after the power is restored.
Solid fuel boilers and biomass – here the backup is most critical
If you heat with a solid fuel boiler (wood, pellets, briquettes, wood chips), the situation is completely different. The boiler can continue to burn even without electricity – the fire will not go out. But if the pump stops, the water will stop circulating and the boiler will start to overheat. The temperature in the boiler can rise above 100 °C within a few minutes, in extreme cases even above 110–120 °C. The result can be the activation of the safety valve, the formation of limescale when cold water is added, and in the worst case, even cracking of the heat exchanger or an explosion. This is not scaremongering – it is a real risk that every solid fuel boiler manufacturer mentions in the documentation. A backup power supply for the pump is practically a necessity when using a solid fuel boiler, not a luxury.
Floor heating – risk of freezing in the cold
Floor heating has a large thermal mass – once the concrete screed is heated, it retains heat for a relatively long time. However, if the house is in a mountainous area, a vacation home that is not continuously occupied, or if the power outage occurs in combination with the owner's long absence, there is a risk that in strong frosts (below -10 °C) damage to the pipes in the corner areas of the floor may occur if the water is standing still. A backup system will extend the time during which the system remains in motion and at the same time allow the thermostat to react to the temperature.
Recreational properties and cottages – long-term absence of the owner
From customer experience, we know that one of the most common situations where a backup power supply really saves the situation is in recreational properties. The owner is in Bratislava, the cottage is in the Low Tatras, it's -15 °C outside, and in the morning on Friday the electricity goes out in the whole village. Without a backup, the heating system stops. If the system contains antifreeze, there will be no immediate damage, but if it contains regular water (which is still found in cottages) and the outage lasts 6–8 hours, the damage can amount to thousands of euros.
Types of backup power sources suitable for circulation pumps
There are several categories of backup power devices on the market. Not all are equally suitable for circulation pumps – it depends on the type of load, the backup time you need, and the type of pump you are powering.
Offline UPS (stand-by)
The simplest and cheapest type. While the grid voltage is stable, the device passes directly through the UPS without any modification. In case of a power outage, it switches to the battery – the switch takes 10–20 milliseconds. For most electronic pumps, this is an acceptable delay. A typical offline UPS power range for a household is 300–1000 VA. Disadvantage: the output voltage during backup is a modified sine wave (not a pure sine), which can cause problems for more sensitive electronics.
Line-interactive UPS
A more advanced type that also stabilizes the grid voltage – if the voltage is slightly higher or lower, the UPS adjusts it without switching to the battery. The switching is also faster. The output can be either modified or pure sine wave, depending on the model. For circulation pumps with frequency inverters (EVOSTA2, EVOTRON), a pure sine wave is an advantage.
Online (dual conversion) UPS
The most expensive type, where the device continuously powers the output through an inverter from the battery, while recharging the battery from the grid. A power outage in the grid is not perceived by the load at all – the switch is zero. The output is always a pure sine wave. For home heating, this is an unnecessarily high performance and cost, but for larger boiler rooms and industrial applications, it makes sense.
UPS with extended runtime
Standard UPS units are sized for 15–60 minutes of backup. For heating systems where you need 4–8 hours of backup (cottages, remote cabins), there are specialized UPS units with external extended battery modules, or solutions built on inverters with car batteries (12V/75–100 Ah).
Which DAB pumps can be combined with a backup power source
Technically, almost every DAB circulation pump can be connected to a backup power source – it is simply a matter of 230 V AC power. However, in terms of proper function, it is important to know what type of electric motor the pump uses, as this determines the requirements for the quality of the output voltage from the backup power source.
DAB EVOSTA2 – EC motor with frequency inverter
EVOSTA2 series pumps belong to the so-called high-efficiency pumps with electronically commutated motor (EC motor). This type of motor is extremely energy efficient (energy class A), but at the same time has more sensitive control electronics that communicate with the frequency inverter. For such pumps, the manufacturer recommends a backup power source with a pure sine wave output. A modified sine wave may work in practice, but it increases thermal losses in the inverter and can cause increased noise or instability in speed. In the worst case, the control electronics may interpret the voltage as faulty and shut the pump down as a fault.
On Atria.sk you can find a SET with DAB.EVOSTA2 40-70/180 pump + backup power source – this is a complete solution where the pump is paired with a compatible backup power source directly from the seller. There is no need to check compatibility separately, which customers from practice highly appreciate. The set includes the EVOSTA2 pump with a power suitable for standard single-family homes (heated space volume of approx. 150–300 m², with standard floor or radiator heating system), fittings for easy pipe connection G 1½", and a backup power source specifically designed for this particular model.
If you do not need a backup power source yet, but plan to add it later, start with a SET with DAB.EVOSTA2 40-70/180 fittings or with fittings and filterball: SET with DAB.EVOSTA2 40-70/180 fittings - FILTERBALL – you can purchase the backup power source at any time. The filterball set also protects the pump from mechanical impurities, which is a topic discussed in more detail in the article DAB pump with filter or without – is the filterball set worth it in this Knowledge Center.
DAB EVOTRON 40/130 – another representative of the EC motor
DAB.EVOTRON 40/130 is a pump with similar EC motor technology, intended more for smaller to medium heating systems (apartment buildings, smaller single-family homes). The same recommendation applies to this model: a backup power source with a pure sine wave, and the minimum power of the backup unit should be at least double the rated power of the pump (with a pump power of 5–25 W depending on the set power, a 150–300 VA UPS is sufficient, but a larger reserve is always better). A detailed comparison of EVOTRON vs. EVOSTA2 can be found in the article DAB EVOTRON vs EVOSTA2 – which pump to choose.
DAB VA35/130 – classic pump with asynchronous motor
DAB VA35/130 is a representative of an older generation of circulation pumps with a classic asynchronous motor. These pumps are less demanding in terms of power supply quality – they usually tolerate a modified sine wave as well. They have a direct start (not a soft start), so the inrush current at startup is higher (the so-called starting current can be 3–5 times higher than the rated power), which must be taken into account when dimensioning the UPS. For VA35/130 with a rated power of around 50–85 W, we recommend a UPS of at least 300–500 VA with sufficient backup capacity.
How to correctly dimension a backup power supply for a DAB pump
Dimensioning a backup power supply is not complicated if you know a few basic parameters. Step by step:
Step 1: Determine the pump power
The rated power is indicated on the pump's nameplate or in the technical documentation. For DAB EVOSTA2 pumps, it is typically 3–45 W (with automatic power setting), for EVOTRON similar values, and for VA35/130 about 50–85 W. Note that EC pumps have power consumption depending on the set performance – at lower performance, they consume significantly less energy.
Step 2: Determine the starting current
For EC pumps (EVOSTA2, EVOTRON), the starting current is usually 1.5–2 times the rated current due to the soft start from the frequency inverter. For asynchronous pumps (VA35/130), calculate with 3–5 times the rated current at startup. The UPS must be able to handle this starting current without triggering the protection.
Step 3: Calculate the required battery capacity
Battery capacity is given in ampere-hours (Ah). The formula for a standard 12V battery: Ah = (Power in watts × Backup time in hours) / (Battery voltage × Inverter efficiency). Example: EVOSTA2 running at 15 W, required backup 6 hours, 12V battery, inverter efficiency 85 %: Ah = (15 × 6) / (12 × 0.85) = 90 / 10.2 = 8.8 Ah. In practice, we recommend a battery of at least 17–20 Ah for a reserve and to compensate for battery aging. For 8 hours of backup, this results in a battery of 26–30 Ah.
Step 4: Do not forget about other consumers
If you want to power the boiler's control electronics, thermostat, or zone valves from the backup power supply, you must add their power consumption. A thermostat typically has a power consumption of 1–5 W, a boiler control board 5–30 W, and an electric thermal actuator of a zone valve 1–3 W during adjustment. In practice, if you want to ensure the entire boiler room, the total load power usually comes to 30–80 W, which at 6 hours of backup means a battery of 25–60 Ah.
Installation of a backup power supply – practical instructions
The installation of a backup power supply is technically simple – most standard UPS units have an outlet into which you connect the pump's power cable. However, there are a few principles that distinguish a correct solution from an improvised one.
Placement of the UPS in the boiler room
The UPS should be placed in a dry, well-ventilated area. Most backup power supplies are sensitive to humidity – the typical relative humidity for operation is 0–90 % non-condensing. In boiler rooms, where vapor or condensation may occur, it is advisable to place the UPS in a closed (but ventilated) distribution box or enclosure. The UPS battery must not be exposed to temperatures below 0 °C (in an unheated space during winter, the battery capacity can significantly decrease).
Size of cabling and fuses
For standard home UPS units (up to 600 VA), existing 230V wiring with 10A fusing is sufficient. Make sure that the outlet into which you connect the UPS is on a separate line from other loads in the boiler room (extraction fans, lighting), so that during a load test of the UPS or backup operation, there are no unintended outages of other circuits.
Functionality test
After installation, always perform a functionality test: disconnect the power supply from the grid (unplug the UPS or turn off the circuit breaker) and observe whether the pump continues to operate without interruption. Modern UPS units usually emit an acoustic signal during backup operation. Also check how long the UPS can maintain the backup – most manufacturers provide approximate times in the documentation. We recommend repeating the test every 6 months and after each deep battery discharge.
Battery replacement
Lead-acid batteries in UPS units have a lifespan of 3–5 years under proper operating conditions. If the UPS indicates a capacity drop (usually LED or acoustic signal), replace the battery without delay. In a boiler room, this is not a luxury – in the event of a real power outage, you will be glad the battery is still fully functional.
Backup power supply vs. backup generator – what is better for a heating system
The question of whether to solve backup power with a UPS or a generator is quite common in practice. Both solutions have different strengths.
A UPS is ideal for short and medium-term outages (15 minutes to several hours), reacts instantly without user intervention, is silent, does not require fuel, and its operation is safe in the boiler room. The disadvantage is the limited battery capacity.
A motor generator can provide practically unlimited backup (as long as it has enough fuel), but it starts with a delay (10–30 seconds), produces significant noise, requires air intake and safe placement, and must not be operated in a closed boiler room (exhaust gases). For a heating system, the delayed start is risky – for a solid fuel boiler, 30 seconds may be enough for the temperature to rise above the critical limit.
An ideal solution for critical installations (solid fuel boiler, mountain recreational building) is a combination of both: UPS covers the first 30–60 minutes immediately, while the generator starts up in the meantime and takes over the backup.
Real examples from practice
From customer experience, we know that a backup power source is an investment that owners either never need (and that doesn't bother them), or they are grateful for saving the boiler or the entire installation. Here are a few typical situations:
Case 1 – house with a pellet boiler: A customer in a mountainous area has a pellet boiler with an automatic feeder and a DAB EVOSTA2 circulation pump. A storm in January cut off the electrical grid for an hour. Thanks to the UPS, the pump operated without interruption throughout the outage. The boiler shut down without electricity (the feeder did not work), but the remaining pellets in the combustion chamber continued to burn without additional air supply and the temperature dropped only to 72 °C. After the power was restored, the boiler restarted automatically. Without the UPS, the boiler could have reached dangerous temperatures within the first 5–10 minutes.
Case 2 – cottage in the Nízke Tatry: A customer heats a remote building with an air-to-water heat pump and DAB circulation pumps. The building is unoccupied during the workweek. A backup power source with an extended battery (80 Ah) supplies the pumps for up to 10 hours. The thermostat in frost protection mode (15 °C) switches the pumps only occasionally, so the actual backup capacity is even longer. Over the past 3 years of operation, the backup was activated five times – once for a 7-hour outage during heavy snowfall.
Case 3 – apartment building with a solid fuel boiler: A building manager was renovating the boiler room. The old coal boiler was replaced with a modern log boiler with an automatic conveyor. The electrician recommended a UPS only for the boiler's control electronics, not for the pump. After the first major outage (20 minutes), the boiler continued to burn without water circulation. The control electronics were still functional, but the pump was not running. The temperature in the boiler rose to 105 °C, the safety valve activated, and cold water entered the system – result: a cracked heat exchanger. Damage: almost 3,000 euros. Conclusion: the entire boiler room should be backed up, not just the control electronics.
Most frequently asked questions (FAQ)
Do I need to register or obtain any permits for a backup power source for a DAB pump?
No. A backup power source (UPS) up to 3 kVA connected to a standard 230V socket does not require any special permits, approvals, or registration. If it is a UPS over 3 kVA, it may be necessary to consult with the electricity supplier, but for home heating we do not encounter such power levels. The entire installation falls within the competence of a certified electrician or even a skilled DIY enthusiast, provided the current standards are followed.
What happens if the backup power source has only a modified sine wave and I connect a DAB EVOSTA2 pump to it?
In practice, the pump will likely run – the frequency inverter of the EVOSTA2 usually works with a modified sine wave. However, the control electronics may experience increased thermal losses, the pump may produce more noise (so-called motor humming), and in exceptional cases, the control board may detect the voltage as unsuitable and go into an error state. DAB therefore recommends a clean sine wave for EC pumps. The risk of using a modified sine wave is borne by the user – including in relation to warranty.
How long will the battery in a backup power source for a DAB EVOSTA2 pump last?
It depends on the battery capacity and the current power consumption of the pump. The EVOSTA2 40-70/180 pump has a power consumption of up to 45 W at full power, but typically operates at 8–15 W in automatic mode. A UPS with an internal 7 Ah battery (standard for a 600 VA UPS) will last approximately 3–4 hours at a load of 15 W (only about 1 hour at full load of 45 W). For longer backup (6–10 hours), an external battery with a capacity of 40–80 Ah or a special extended runtime UPS is required.
Is the backup power source included in the package with the DAB.EVOSTA2 40-70/180 and heating from Atria.sk?
The backup power source is included only in one specific version of the package – PACKAGE with DAB.EVOSTA2 40-70/180 and backup power source. Other versions of the package (basic package and package with filterball) do not include the backup power source – it can be purchased separately later.
Can I power the boiler from the backup power source, not just the pump?
Yes, provided the UPS power is sufficient and the output voltage meets the boiler's requirements (usually a clean sine wave). In practice, it is advisable to dimension the backup power source for all critical boiler room consumers at once – the pump, boiler control electronics, thermostat, and possibly zone valves. The total power consumption of these devices in a standard home boiler room ranges from 30 to 120 W, which is a normal load for a UPS with a power of 600–1000 VA.
Which backup power source do you recommend for a solid fuel boiler with a DAB VA35/130 pump?
For the asynchronous DAB VA35/130 pump with a power consumption of 50–85 W, we recommend a UPS with a minimum power of 500 VA (ideally 800 VA due to the starting current) and a battery capacity dimensioned for the required backup time. For solid fuel boilers, where backup is critical for safety, we recommend a minimum of 2 hours of backup – at a power consumption of 85 W, this corresponds to a battery with a minimum capacity of 20 Ah (12V system). More about this pump can be found directly on the product page DAB VA35/130.
Conclusion – a backup power source is not a luxury, but insurance
A backup power source for a DAB circulation pump is an investment that often seems unnecessary in everyday practice – until the moment when you actually need it. For solid fuel boilers, it is a matter of installation safety and the physical integrity of the boiler. For condensing boilers, it is about comfort and smooth operation. For recreational properties and cottages, backup can be the difference between discomfort and a real material loss in the thousands of euros.
A well-designed backup system – a properly dimensioned UPS with a clean sine wave, sufficient battery capacity, and regularly maintained – is a solution that works quietly in the background for years. And that is what is best about it: if it works well, you will never notice it. But when the time comes, it will be there.
If you are considering selecting a pump, you are wondering what power you need for your home, or you want to know more about the differences between models, we recommend other articles in this Knowledge Center: How to choose a DAB circulation pump for heating, What pump power do I need for my home, Energy class A DAB pumps – what it means and why it is worth it, and also Installation of a DAB circulation pump step by step, where you will also find practical information about connecting the backup system to the boiler room electrical diagram.
Do you have a question about this topic?
Not sure or dealing with a specific situation in your home? Write to us – we are happy to help.