Product detailed description

ATTACK Heating Circulation Pump PR 25/6, 180 mm, Class A

Universal electronic circulation pump of class A with a construction length of 180 mm, designed for domestic and smaller commercial heating circuits with a circulation pump in the main distribution, in a mixing circuit, or directly at the boiler. Thanks to its standard construction length and 1½" connection thread, it is suitable as a replacement for most common circulation pumps with the same axial connection spacing, including installations with ATTACK boilers.

The pump is primarily intended for new installers and service technicians who need a reliable and energy-efficient solution for a mixing or main heating circuit without being tied to a specific boiler brand – thanks to its universal connection, it can be used with most common boilers, heat exchanger stations, and heating manifolds.

Why does energy class A matter?

The circulation pump is one of the few devices in a heating system that runs practically continuously throughout the entire heating season during normal operation – in practice this can be as much as 4,000 to 5,000 hours per year. That's why its efficiency has a much greater impact on annual electricity costs than might seem obvious at first glance. Older pumps without electronic regulation (so-called "three-speed" wet-rotor pumps) always run at full or fixed power regardless of the actual heat demand at a given moment, and their energy efficiency index (EEI) typically ranges around 0.6 – 0.8 or is not declared at all.

This pump belongs to energy class A, the highest commonly available class for small circulation pumps in domestic heating circuits, with a corresponding EEI ≤ 0.20. In practice, this means that the electronically controlled rotor with permanent magnets automatically adjusts speed and flow rate to the current needs of the heating circuit – under partial load (for example on transitional autumn or spring days), the pump significantly reduces power consumption instead of constantly running at full power. When replacing an old unregulated pump with this model, real electricity savings for circulating heating water can range from 50 to 80%, depending on the original pump type and the nature of the heating system.

Lower electricity consumption of the pump is also noticeable outside the heating season if the circulation pump is also used for run-on or temperature maintenance in systems with a storage tank. With year-round operation, the savings become even more significant, and the investment in a quality class A pump typically pays for itself within a few heating seasons through electricity savings alone, not to mention quieter and more reliable operation.

Construction length 130 mm vs. 180 mm – why it matters

Circulation pumps for domestic heating circuits are not manufactured in a single universal length – you will commonly encounter two most widespread axial distances between the connection threads (the so-called construction length, "Baulänge" in German): 130 mm and 180 mm. This dimension must exactly match the distance between the inlet and outlet ports in the boiler body or in the piping to which the pump is being fitted – a pump of shorter or longer construction length simply will not fit between the existing connections without modifying the piping.

How to determine which length you need:

• When replacing the original pump, measure the distance directly between the centers of both flange/thread connections of the original pump (from the center of one thread to the center of the other).
• Check the type label of the original pump – the construction length is usually part of the type designation (e.g. "25/6-130" or "25/6-180").
• For ATTACK boilers, you can find the recommended pump type and size in the service documentation or the boiler's hydraulic wiring diagram, or contact our customer service with the boiler's serial number.
• Never install a pump of the wrong construction length with the intention of "compensating" using the union nuts over the gasket – this risks leaks, stress on the piping, and thread damage.

The connection thread on the pump body is generally 1½" in both versions (internal, for a union nut with gasket), so the connection to the piping itself is the same for both lengths – only the distance between the connections differs, not the thread type.

Universal use across a wide range of installations

Unlike original OEM replacement parts, which are structurally and software-adapted to a specific boiler type, this PR 25/6 pump is designed as a universal solution suitable for:

• the main heating circuit downstream of the boiler (direct circuit without mixing),
• a mixing circuit with a three-way or four-way valve (e.g. in combination with DPP series products or OT02/OT44 three-way valves),
• underfloor or radiator heating manifolds with higher hydraulic resistance,
• replacement for an older, unregulated, or faulty pump of another brand with the same construction length of 180 mm and 1½" thread.

The 180 mm construction length is one of the two most common construction lengths on the market (along with 130 mm) and corresponds to the connection spacing historically used in several ATTACK boiler models and many other heating equipment brands sold on the Slovak and Czech markets. Before ordering, we therefore always recommend verifying the actual connection spacing on your equipment according to the procedure described below.

Technical parameters

• Construction (installation) length: 180 mm
• Energy class: A (EEI ≤ 0.20)
• Electrical power input: 3 – 45 W, continuously regulated
• Maximum head: 6 m
• Maximum flow rate: up to 3.5 m³/h
• Connection: 1½" internal thread, union nut
• Medium temperature range: 2 – 110 °C
• Power supply: 230 V / 50 Hz, IP44 protection

How to read the circulation pump's type label

The type label is affixed directly to the body of the pump's electronic head and contains all the information needed for clear identification when ordering a replacement. In addition to the manufacturer's type designation (e.g. RS 25/6, Yonos PARA RS25/6), you will also find the construction length there (often directly in the number after the slash or in a note below the type), the supply voltage range, maximum power input, IP protection rating, and the serial/production number of the specific unit.

If the label is no longer legible (for example after years of operation in the humid environment of a boiler room), the most reliable method is to directly measure the construction length with a caliper or to contact our customer service with the serial number of the ATTACK boiler itself – from this we can look up which pump was factory-fitted to that particular boiler.

When it's time to replace a circulation pump

A circulation pump is one of the components that usually doesn't fail suddenly, but its performance and reliability gradually deteriorate with years of operation. Here are a few symptoms to watch for:

• Uneven heating – some radiators or circuits are noticeably colder than others even with thermostatic heads fully open, which may indicate insufficient pump flow capacity.
• Increased noise – humming, squeaking, or knocking during operation that doesn't disappear even after thorough bleeding of the circuit usually indicates worn bearings.
• Frequent thermal cutoff tripping or outages – may indicate mechanical seizure of the rotor or an electrical fault in the motor winding.
• Visible leakage at the joints or in the shaft area – the seal or gasket may wear out after years of operation.
• High electricity consumption compared to declared values – an older unregulated pump without class A rating may consume several times more energy than a modern electronically controlled solution.

If any of these symptoms occur, we recommend replacing the pump before it fails completely, which could cause the boiler to overheat or heating to fail at the most inopportune moment of the heating season.

Installation and assembly – practical procedure

Replacing or installing a circulation pump itself is not complicated, but it requires following a few principles that affect the pump's service life as well as the trouble-free operation of the entire heating circuit:

1. Shutting down and draining the circuit. Before removing the old pump or installing a new one, close the ball/shut-off valves on both sides of the pump (if fitted) and drain the water from the relevant section of the circuit to minimize medium leakage and contamination of the boiler room.
2. Checking the flow direction. The pump body has an arrow indicating the flow direction – the pump must be installed exactly in the direction of the heating water flow, otherwise it will not work efficiently or at all.
3. Orientation of the motor head. The pump's electronic head (terminal box and control panel) must be oriented horizontally after installation, never facing downward – this prevents condensate or any water leakage from entering the electronics. On horizontal piping, the head is usually rotated to a side position.
4. New gaskets. Use new flat gaskets under the union nuts with every pump replacement – worn original gaskets are the most common cause of microscopic leaks after servicing.
5. Filling and bleeding. After screwing in and tightening the connections, slowly fill the circuit with water with the shut-off valves open, and bleed the system through the bleed valves at the highest points of the system as well as through any bleed screw on the front of the pump rotor (if included in the design).
6. Checking tightness and function. After starting the boiler and the pump running up, check the tightness of both connections, the absence of unusual noise (humming may indicate air in the pump), and correct function of the automatic power regulation when the heat load changes.

Electrical connection should always be left to a person with appropriate qualifications (electrician or service technician) – the pump is connected to a 230 V mains voltage, and in boiler applications it may be powered directly from the boiler's control electronics.

Maintenance and extending pump life

Electronically controlled circulation pumps of this category are practically maintenance-free – they contain no lubrication points or parts requiring regular servicing beyond routine inspection. Nevertheless, a few simple habits will significantly extend their service life and maintain the declared energy class A throughout their operating life:

• Quality of heating water. Excessive sludge, rust, or air in the heating circuit is the most common cause of premature wear of the impeller and bearings of the wet-rotor motor. For older or recently plumbed systems, we recommend considering fitting a dirt filter or sludge separator before the pump.
• Regular visual inspection. Once per heating season, check the tightness of the connections, the absence of corrosion marks on the pump body, and unusual noises (humming, knocking) that may indicate air in the system or a developing bearing fault.
• Short-term shutdown out of season. If the pump is not operating for a long period (e.g. outside the heating season in systems without year-round circulation), it is recommended to run it briefly from time to time to prevent the rotor from "seizing" due to deposits after prolonged inactivity – most modern pumps handle this automatically with a built-in periodic self-test.
• Frost protection. In unheated spaces (e.g. decommissioned cottages, technical rooms without heating), if there is a risk of frost, you must either ensure the circuit is drained or use an antifreeze mixture with declared compatibility with the pump materials.

Safety warnings

Before any intervention on the pump, always disconnect the 230 V power supply and wait until the pump body has cooled sufficiently – heating water can reach a temperature close to 90 °C, and there is a risk of burns. Electrical connection may only be carried out by a person with appropriate electrical qualification in accordance with applicable standards (STN 33 2000 and related). The pump is not intended for operation outside the declared temperature and pressure range of the medium stated in the technical parameters – exceeding these limits may damage the pump and endanger operational safety.

Frequently asked questions

Is this pump suitable for direct use in an ATTACK boiler?
Yes, provided the connection spacing in your boiler is 180 mm and the connection thread is 1½". For ATTACK boilers, we recommend verifying the specific type using the serial number, as some boiler series also use a 130 mm variant (see OT01C).

What is the difference compared to the OEM replacement part WILO Yonos PARA (OT180A)?
Both types are functionally very close in parameters (class A, head, flow rate, dimensions). The OT180A OEM part is an original component identical to the one factory-fitted in specific ATTACK boiler series, while this PR 25/6 pump is a universal solution suitable for a wider range of installations, including other brands.

Can the pump be installed in vertical piping as well?
Yes, the pump can be installed in both horizontal and vertical piping sections; however, the orientation of the terminal box/electronic head must always be horizontal (never facing downward), and the flow direction indicated by the arrow on the body must be respected.

How can I tell that the pump is operating in energy-saving mode?
The electronic regulation continuously adjusts the impeller speed according to the current needs of the circuit – this is not always visually noticeable, but it manifests mainly in lower power consumption (measurable e.g. with a wattmeter in the socket) and quieter operation compared to an older unregulated pump.

Do I need shut-off valves before and after the pump?
They are not mandatory for the pump's function, but we strongly recommend them – they will significantly simplify future replacement or servicing without having to drain the entire heating circuit.

Are gaskets and union nuts included in the package?
Yes, the pump is supplied complete with the union nuts and gaskets needed for standard installation on a 1½" thread.

Can the pump be used in a circuit with a glycol-based antifreeze mixture?
Wet-rotor pumps of this type generally tolerate water-glycol mixtures up to a concentration of around 20–30%, but we always recommend verifying the specific resistance according to the manufacturer's instructions and the type of glycol used.

Is the pump noisy when starting up after a long shutdown?
Brief humming during the first start-up is normal and is usually related to air trapped in the pump body – this noise disappears after properly bleeding the circuit. Persistent noise may indicate the need for further bleeding or a bearing check.

Can the pump's output be limited if the circuit is small and the pump seems oversized?
Yes, thanks to electronic regulation and selectable operating modes, the pump's operating point can be reduced directly on the control panel, allowing it to adapt to smaller or hydraulically simpler circuits without having to replace the entire pump.

Summary

The ATTACK PR 25/6, 180 mm is a reliable choice for anyone who needs an energy-efficient and quiet class A circulation pump for the main or mixing heating circuit, without being limited to a single boiler brand. When replacing the original pump, always remember to verify that the construction length of 180 mm and the 1½" thread match.

Warranty and support

We provide a 24-month warranty from the date of dispatch from the warehouse for this product. The warranty covers manufacturing and material defects provided the installation and operating conditions stated in the enclosed manufacturer's manual are observed. If you have any questions about selecting, compatibility, or installing the pump, please do not hesitate to contact our customer service – we will be happy to help identify the correct type based on the serial number of your ATTACK boiler or the parameters of your heating circuit.

We recommend keeping your proof of purchase, and in the event of a service intervention on an ATTACK boiler, also stating the boiler's type designation and serial number – this will speed up any warranty claim process as well as future identification of replacement parts.