What do the numbers in the IBO pump name mean – how to read model technical codes
Why it is important to understand pump designation
When a customer first opens the catalogue of IBO circulation pumps or browses products on atria.sk, they come across names like IBO OHI 25/60-130 or IBO OHI 15-60/130. At first glance, these combinations of numbers and slashes look like a code. In reality, it is a systematic technical code that instantly tells an experienced installer or a technically savvy homeowner everything essential – the connection diameter, the maximum discharge head, the length of the motor section, and which system the pump belongs to.
The problem arises precisely when a customer chooses a pump based on price or "gut feeling", without understanding what the individual numbers mean. Practice shows clearly: an incorrectly sized pump won't heat the house any cheaper. Either it is too weak and the heating system can't balance the heat losses, or it is unnecessarily powerful, noisy, and consumes more electricity than necessary. In both cases, the customer pays unnecessarily – either for an underperforming product or for excess power.
This article will guide you through every part of the technical designation of IBO OHI series pumps, step by step, with real examples and practical scenarios from everyday installation practice. If you want to go even deeper into choosing a specific model, this topic is followed up by the article How to choose an IBO circulation pump for your heating system in the same Knowledge Center.
Manufacturer and product family: IBO and the OHI series
The first abbreviation is simple: IBO is the name of a Polish pump manufacturer based in Toruń. The company has been operating since 1988 and today is one of the established European manufacturers of pumps for heating, domestic hot water, and industrial applications. On the Slovak market, IBO pumps are available as an affordable alternative to German premium brands (Grundfos, Wilo), while the technical parameters are fully comparable to these brands in the same price category. If you're interested in this topic in more depth, you'll find the article IBO circulation pumps vs. Grundfos and Wilo – comparison of parameters and price in the same Knowledge Center.
The second abbreviation, OHI, denotes a specific series in the IBO portfolio. These are wet-rotor circulation pumps whose rotors are cooled by the pumped liquid – meaning there is no mechanical seal separating the rotor from the motor. This design principle is now the standard for circulation pumps in heating systems, solar circuits, and cooling circuits. The term "wet-rotor" (also called glandless) means, among other things, that the bearings are lubricated directly by the pumped medium – water. This eliminates the need for regular lubrication, reduces noise levels, and extends the service life of the entire unit.
The OHI series in IBO's production program is primarily intended for:
- hot-water heating systems (boiler + radiators, underfloor heating)
- solar thermal circuits (using special glycol-resistant variants)
- heat pump circuits
- domestic hot water (DHW) circulation circuits
The first number: connection diameter (DN) – what exactly "15" or "25" means
After the abbreviation OHI comes the first number. In cases such as OHI 15-60/130, this is the number 15; in cases such as OHI 25/60-130, it is the number 25. This number indicates the nominal diameter of the flange or thread through which the pump is connected to the piping – technically referred to as the DN (Diameter Nominal) or Rp (thread size according to ISO) value.
Specifically:
- DN 15 = internal pipe diameter 15 mm, external thread G ½" (= Rp ½") – typical for smaller household systems, apartments, smaller boilers
- DN 25 = internal pipe diameter 25 mm, external thread G 1" (= Rp 1") – typical for family houses, larger apartments with underfloor heating, larger boilers
In practice: If you have a Viessmann Vitodens 100 boiler with G ½" outlets and an old Grundfos UPS 15-50 with DN 15, you're looking for a replacement in the DN 15 category. If you have a 180 m² house, a boiler with G 1" outlets and 28-32 mm copper piping, you're working with DN 25. Interchangeability between DN 15 and DN 25 is technically possible using reducers, but it is not correct – a reducer increases hydraulic resistance and worsens the hydraulic characteristics of the entire circuit.
The second number: maximum discharge head – what "40", "60" and similar values mean
After the slash or dash following the DN comes a value that indicates the maximum discharge head of the pump in units of dm H₂O (decimeters of water column) – which is directly equivalent to values in kPa (1 dm H₂O = 1 kPa ≈ 0.01 bar). This value is sometimes also referred to as the manometric head or delivery head.
Numbers you'll encounter in the IBO OHI range:
- 40 = max. 4.0 m H₂O (40 kPa, 0.4 bar) – suitable for simple, well-balanced systems with short pipe runs
- 60 = max. 6.0 m H₂O (60 kPa, 0.6 bar) – a universal value for most family houses with radiators
Note: the number in the name indicates the maximum discharge head at zero flow. At the operating point where the pump actually works, the discharge head is lower and the flow rate correspondingly higher. The manufacturer provides characteristic Q-H curves (flow – head) for this purpose, which are used to make the correct hydraulic selection. The calculation of the required pump output is discussed in detail in the article What circulation pump output do I need – calculation based on area and system.
A practical example from job experience: A house with an area of 120 m², a hot-water circuit with copper pipes DN 20, 8 radiators, total pipe length approx. 60 m. Hydraulic calculation shows a pressure loss in the circuit of around 4.2–4.8 m H₂O. The correct choice is a pump with a maximum of 60 dm (= 6 m H₂O), not 40 dm – a pump with 40 dm would operate at the upper edge of the curve and constantly struggle with insufficient pressure, which would manifest as uneven heating and possibly noise. Among the models on atria.sk, the IBO OHI 25/60-130 is suitable for this case.
On the other hand: oversizing is also harmful. For a smaller apartment with a pipe run length of 20 m and a pressure loss of around 2.5 m H₂O, buying a pump with a 60 dm head and regulating it to the minimum is an unnecessarily expensive solution. For such cases, the correct choice is a pump with a lower maximum head and a suitable diameter (DN 15). An example of this is the IBO OHI 15-60/130, where the number 60 again indicates the maximum discharge head, but DN 15 limits the maximum flow rate to values suitable for smaller systems.
The third number: installation length – what "130" or "180" means
The last number in the designation is most often misunderstood, and yet it may be the most important factor when replacing a pump: it refers to the installation length (or fitting length) in millimeters. It is the distance between the flange axes (the connecting surfaces where the pump is bolted into the piping).
Standard values in the OHI series:
- 130 mm – shorter variant, much more common, corresponds to the old European standard for household circulation pumps (originally defined for Grundfos UPS series pumps)
- 180 mm – longer variant, used for larger models or where physical space in the piping requires it
Installation length is crucial when replacing an existing pump. If you have an old Grundfos UPS 25-60 with an installation length of 130 mm in your boiler room, the new pump must also have 130 mm – otherwise it will not physically fit between the flanges without cutting or extending the pipe. In practice, this means always measuring the existing pump before ordering. Swapping 130 mm for 180 mm requires cutting the pipe, inserting spacers, and welding or pressing fittings – which, when replacing a pump, increases labor and material costs by at least €50–80, sometimes more.
For example:
- IBO OHI 25/40-130 – DN 25, max. head 40 dm H₂O, installation length 130 mm
- IBO OHI 25/40-180 – DN 25, max. head 40 dm H₂O, installation length 180 mm
- IBO OHI 25/60-180 – DN 25, max. head 60 dm H₂O, installation length 180 mm
These three models have the same connection diameter and can be hydraulically compared. However, their installation length is different – and this is exactly the detail that matters when replacing a pump without modifying the piping.
Special cases: what if the slash is in a different position in the name
Compare these two names:
- IBO OHI 15-60/130 – here a dash is between DN and head, and a slash separates head from installation length
- IBO OHI 25/60-130 – here a slash is between DN and head, and a dash separates head from installation length
Confusing at first glance. In practice, it's just a matter of typographical convention – different generations of manufacturers and distributors write the same structure differently. IBO uses both forms in its internal documentation depending on the product series and year of manufacture. The physical and hydraulic content of both notations is identical: the first number = DN, the second = max. head, the third = installation length. In case of any doubt, the technical data sheet of the specific model or direct consultation via atria.sk will help.
Practical table: what the numbers tell you about pump suitability
| Model | DN (connection) | Max. head | Installation length | Typical use |
|---|---|---|---|---|
| IBO OHI 15-60/130 | 15 mm / G½" | 6.0 m H₂O | 130 mm | Smaller apartment, bungalow, boiler up to 20 kW |
| IBO OHI 25/40-130 | 25 mm / G1" | 4.0 m H₂O | 130 mm | Family house 80–120 m², short piping, new house with underfloor heating |
| IBO OHI 25/40-180 | 25 mm / G1" | 4.0 m H₂O | 180 mm | Family house 80–120 m², longer space in the piping |
| IBO OHI 25/60-130 | 25 mm / G1" | 6.0 m H₂O | 130 mm | Family house 120–200 m², long piping, combination of radiators and underfloor heating |
| IBO OHI 25/60-180 | 25 mm / G1" | 6.0 m H₂O | 180 mm | Family house 120–200 m², longer installation length in the boiler room |
What the designation doesn't tell you – additional parameters that matter
The numerical designation is powerful, but it doesn't tell you everything. There are parameters you can't read from the name and need to verify in the technical data sheet:
Maximum medium temperature
Standard IBO OHI circulation pumps are designed for a heat transfer fluid up to 110 °C. Most boilers in family houses operate at an outlet temperature of 70–80 °C, which is safely within the norm. If you have a system with temperatures above 90 °C (for example, industrial superheated water), you need to check the thermal classes of the insulation and bearings.
Maximum working pressure
Most OHI models are designed for a system pressure of up to 10 bar. A family house typically operates at 1.5–2.5 bar. If you have a high-rise building or a system connected to a central heat source with higher system pressure, a special variant needs to be selected.
Number of speed settings
IBO OHI pumps are three-speed – they have three fixed speed settings (I, II, III), each corresponding to a different Q-H characteristic. Setting I is the most economical and quietest, setting III is the most powerful. For a typical family house, setting I or II is sufficient for most of the season; setting III is used only during extreme frosts or during initial filling and venting of the system.
Power input and energy efficiency class
You cannot tell from the name how many watts the pump consumes. IBO OHI pumps belong to energy class A, which corresponds to European regulation ErP 2013/814. Power input depends on the speed setting: at setting I it is typically 45–65 W, at setting III 80–110 W (specific values vary by model). In everyday operation, this means an annual consumption of around 400–600 kWh, which, at an electricity price of €0.20/kWh, represents €80–120 per year. For comparison: old class E, F pumps had a power input of up to 150–200 W and an annual consumption of 1,300–1,750 kWh.
Degree of protection (IP rating)
Standard is IP44 – the pump is protected against the ingress of solid objects larger than 1 mm and against splashing water from all directions. For installation in dry boiler rooms, this is a sufficient protection level. For humid environments (for example, near a condensation zone), we recommend checking the current technical data sheet of the specific series.
Comparison of the IBO designation format with other manufacturers
When comparing IBO with Grundfos or Wilo, you may initially get confused because each manufacturer uses a slightly different convention. Grundfos uses the format UPS 25-60 130 or ALPHA2 25-60 130 – which is essentially the same logic (DN-head-installation length). Wilo uses the format Yonos PICO 25/1-6, where the number after the slash is the maximum discharge head written differently (6 m H₂O = 60 dm). IBO follows the classic European format similar to Grundfos, which makes direct compatibility easier when replacing a pump.
Practical consequence: if you replace a Grundfos UPS 25-60 130 with an IBO OHI 25/60-130, this is a physically compatible replacement – same installation length, same DN, same maximum discharge head. The Q-H hydraulic characteristics are very close (small differences exist, but they are within the normal tolerance for family houses). You can read more about this topic in the article IBO circulation pumps vs. Grundfos and Wilo – comparison of parameters and price.
Mistakes when choosing a pump based on numbers – what we most often see in practice
Over the years of selling circulation pumps, these typical mistakes keep recurring:
Mistake 1: Mixing up installation length without measuring
The customer orders 180 mm instead of 130 mm simply because they confused the models. The pump arrives, and the installer cannot mount it without cutting the pipe. This problem costs time, money, and delay. Solution: always measure the existing pump before ordering – a tape measure is enough, measuring from flange axis to flange axis.
Mistake 2: Choosing based on discharge head alone without considering flow rate
The customer sees that they need a 5 m H₂O head and immediately orders a pump with a maximum of 60 dm. They don't notice that at 5 m H₂O and DN 15, the flow rate is only 1.2 m³/h, which is not enough for a house with underfloor heating on 150 m². You need to look at the entire Q-H curve, not just the maximum.
Mistake 3: Changing DN without modifying the piping
The customer has DN 15 piping and buys a DN 25 pump, thinking "bigger is better". The result is a reducer in the piping, local turbulence, and increased noise levels. Correct approach: the pump must have the same DN as the existing piping, or the entire pipe section needs to be modified.
Mistake 4: Ignoring energy class when replacing old pumps
The customer has a 20-year-old class F pump (150 W) and replaces it with the cheapest model available, regardless of class. In the IBO OHI range, all models are class A, so there's no risk of buying an underperforming class here, but with other brands, this needs to be checked.
How to correctly read the label on an existing pump
Before ordering a replacement pump, we recommend creating a "record of the existing pump". Five minutes in the boiler room with a smartphone is enough:
- Photograph the manufacturer's label – it contains all parameters including the serial number and year of manufacture
- Measure the installation length – a tape measure from flange axis to flange axis (not from edge to edge of the housing)
- Verify the DN – by comparing it with the corresponding thread sizes: G ½" = DN 15, G ¾" = DN 20, G 1" = DN 25
- Check the pump position – whether the motor axis is horizontal (standard position) or vertical (requires special models)
- Record the current speed setting – setting I, II, or III
You can read about the correct installation procedure in the article Installing an IBO circulation pump – procedure, installation position, and connection.
Frequently Asked Questions (FAQ)
What does the number 130 or 180 mean in the name of an IBO pump?
This number indicates the installation length of the pump in millimeters – specifically the distance between the flange axes (connection surfaces). It is the most important dimension when replacing an existing pump, because the new pump must have the same installation length to physically fit without modifying the piping. Always measure the existing pump before ordering.
What does the number 25 mean in IBO OHI 25/60-130?
The number 25 indicates the nominal connection diameter (DN 25), which corresponds to a G 1" thread (Rp 1"). It tells you what pipe size the pump is designed for. Models with the number 15 have a G ½" thread and are suitable for smaller systems and smaller boilers.
Is the IBO OHI 25/60-130 pump a direct replacement for the Grundfos UPS 25-60 130?
Yes, in terms of physical connection and hydraulic parameters, this is a compatible replacement. Both models have DN 25, a max. discharge head of 6 m H₂O, and an installation length of 130 mm. The Q-H characteristics are very close. Minor differences in output at individual settings will not affect functionality in a typical family house.
How do I know which IBO OHI model I need if I don't know the hydraulics of my system?
The simplest approach: find out the type and output of the boiler, the heated area of the building, and the type of piping (radiators or underfloor heating). For houses up to 120 m² with radiators, OHI 25/40 is usually sufficient. For houses of 120–200 m² or combined systems with underfloor heating, we choose OHI 25/60. You can find a more detailed procedure in the article What circulation pump output do I need – calculation based on area and system.
Why do some models have a slash and others a dash between the first and second number?
It's just a typographical convention, not a technical difference. Different generations of documentation and distributors write the same parameter structure with a slash or dash in different places. It always applies that: the first number = DN, the second number = max. head in dm H₂O, the third number = installation length in mm.
Can I use an IBO OHI pump in a DHW heater instead of a heating circuit?
Yes, pumps in the OHI series are also suitable for domestic hot water (DHW) circulation in the temperature range up to 110 °C. However, it should be noted that in a DHW system, the internal parts of the pump come into contact with drinking water – verify that the specific model has drinking water certification, or use a special DHW variant. Standard OHI models intended for closed central heating circuits may not have this certification.
Conclusion: The numerical code as your technical guide
The designation of an IBO circulation pump is not a random string of digits. It is a compressed technical description that – if you know how to read it – tells you everything essential even before you open the technical data sheet. The first number indicates the connection size (DN 15 or DN 25), the second number indicates the maximum discharge head in dm H₂O (40 or 60), and the third number defines the installation length in millimeters (130 or 180).
Reading the designation correctly will save you time when choosing, money during installation, and worry during operation. Always combine reading the name with a specific hydraulic calculation of your system and with verifying the installation length of the existing pump. If you are unsure, the product page of each model on atria.sk contains complete technical data sheets with Q-H curves, exact dimensions, and other parameters that will help you make the right decision.
Do you have a question about this topic?
Can't decide or are you dealing with a specific situation in your household? Write to us - we'll be happy to help.