Product detailed description

ATTACK Three-Way Valve FUGAS Complete 3/4" for Connecting an External DHW Tank

A complete assembly of a three-way diverter valve made by FUGAS, with a 3/4" connection thread and a motorized actuator, designed to switch the flow of heating water between the heating circuit and the charging circuit of an external domestic hot water (DHW) tank in ATTACK boilers with low to medium output.

Function of the Three-Way Diverter Valve in a System with an External Tank

If a boiler does not have its own built-in instantaneous water heater and hot water is prepared in a separate (external) storage tank, the boiler's control electronics need a way to switch the flow of heating water between two branches – the radiator/underfloor circuit and the charging circuit of the heat exchanger in the tank. This task is performed by a motor-driven three-way valve.

The switching signal comes directly from the boiler board based on the temperature sensor in the DHW tank – when the temperature drops below the set value, the valve turns to the "tank charging" position, and once the target temperature is reached, it returns to the "heating" position. Thanks to adjustable priority (usually DHW before heating), fast availability of hot water is ensured without unnecessarily interrupting heating for a longer period.

Operating Principle of the Diverter Three-Way Valve

Inside the valve body there is a rotary control element that, depending on its position, connects the inlet port to either the first or the second outlet port. The servo actuator mounted on top of the valve body converts the electrical control signal from the boiler board into mechanical rotation of this element between the two end positions.

Unlike mixing valves, which combine two input flows into a single output in any variable ratio (typically in mixing heating circuits), this type of valve operates purely as a diverting valve – at any given moment it directs the entire flow either into the heating circuit or into the DHW tank charging circuit, never simultaneously into both in a partial ratio.

Why FUGAS Complete 3/4" and Not the 1" Size

This valve is supplied in the smaller 3/4" size, suitable for boilers with low to medium heating output or for installations where the flow rate between the boiler and the DHW tank does not need to be as high as with the 1" version (see OT02). FUGAS is a proven Italian brand of control and switching technology, commonly used as an alternative to Honeywell in smaller sizes.

As with the larger variant, the term "complete" in the name means that the delivery includes the entire assembly – both the valve body and the motorized actuator, ready for immediate connection to the ATTACK boiler control electronics.

Technical Parameters

• Connection thread: 3/4" (internal)
• Type: three-way diverter valve with motorized actuator, complete assembly
• Brand: FUGAS
• Actuator power supply: 230 V, controlled directly from the ATTACK boiler board
• Maximum operating temperature of the medium: up to 110 °C
• Maximum operating pressure: PN 10
• Body material: brass
• Switching time (position change): approx. 4–8 seconds

Where the Valve Is Located in the System

In a typical hydraulic scheme, the three-way diverter valve is placed right after the boiler outlet, before the split into individual heating branches or before the manifold. One outlet leads to the heating distribution, the other to the charging circuit of the DHW tank heat exchanger.

The actuator's electrical connection leads directly to the boiler control board, to the terminal block designated by the manufacturer for the DHW three-way valve – the exact terminal designation can be found in the wiring diagram supplied with the ATTACK boiler. Switching control is automatic, based on the signal from the temperature sensor in the tank.

Which ATTACK Boilers This Part Is Intended For

This part is intended for service ranges of ATTACK boilers with an external DHW tank that use the corresponding valve connection size from the factory. Since the specific size and type of diverter valve may change across production series, we recommend verifying compatibility according to your boiler's serial number with our customer service before ordering.

Installation and Connection

1. Shutting off the circuit by closing the shut-off valves and draining the relevant section before removing the original part or installing the new one.
2. Checking the flow direction – the three-way valve has precisely defined inlet and two outlet ports (or two inlet and one outlet port, depending on the connection) marked on the body; incorrect port connection will cause non-functional or incorrect switching between circuits.
3. Mechanical installation of the valve body onto the thread, with new gaskets on both sides.
4. Fitting and securing the actuator (in complete assemblies OT02/OT44) onto the valve body according to the instructions, usually by simply sliding it on and securing it with a retaining clip or screw.
5. Electrical connection of the actuator to the boiler control board according to the wiring diagram supplied with the boiler – this step must be carried out by a qualified person (electrician or boiler service technician).
6. Filling, venting and functional test – after starting the boiler, test the valve switching by forcing a DHW heating demand (e.g. by lowering the set tank temperature and then raising it again) and observe whether the valve visibly switches and the system starts heating the tank.

When It's Time to Replace the Three-Way Valve

• Insufficient or slow DHW heating despite the boiler working correctly and the priority set properly – the valve may not be switching reliably into the tank-charging position.
• Simultaneous heating of both circuits at once (radiators and tank both lukewarm/insufficiently hot) – indicates a leaking or mechanically stuck valve body that does not switch fully into the end position.
• Audible clicking or buzzing of the actuator without visible movement of the valve – usually indicates a worn actuator gearbox.
• Boiler error message relating to the diverter valve or DHW circuit on the control unit display.
• Visible leakage at the joint between the valve body and the piping after years of operation.

Diagnosing Typical Faults

• Valve not switching – first check the supply voltage and the signal wire between the actuator and the boiler control board; if these are fine, the cause is usually a mechanical fault inside the actuator itself.
• Incomplete switching to the end position – manifests as simultaneous, though weaker, heating of both circuits; usually indicates wear of the sealing element inside the valve body.
• Increased noise during switching – slight clicking is normal; more pronounced and increasing noise should be addressed with a preventive replacement before the function fails completely.
• Leakage at the pipe joint – check the condition of the gaskets at the union nuts; after years of operation it is advisable to replace them during any service intervention.

Safety Notices

Always carry out service work after disconnecting the boiler from the electrical mains and letting the circuit cool to a safe temperature. Entrust the electrical connection of the actuator to the boiler control board exclusively to a qualified person – incorrect wiring can damage the boiler's electronics or cause incorrect, potentially unsafe switching between circuits.

How to Choose and Order the Right Part – Checklist

• Verify the connection size of the original valve (1" or 3/4") by directly measuring the thread or checking the ATTACK boiler's rating plate.
• Decide between a complete assembly and a standalone body – if the original actuator is still working and only the body is damaged, it is enough to order the body without the actuator (type VC); if the actuator is also damaged or you cannot verify its condition, order the complete assembly.
• Have the boiler's serial number ready before contacting customer service, as this speeds up verification of correct compatibility.
• Plan a shutdown of heating/DHW for the duration of installation – the service intervention usually takes up to one hour, but requires briefly draining the relevant section of the circuit.
• Consider a preventive replacement of gaskets at surrounding joints as well, if they show visible wear, to avoid a repeat service call in the near future.

Is Repair Worthwhile, or Is Replacement with a New Part Better?

In the event of a three-way valve failure, the question of repair versus replacement is usually clear-cut in practice – neither the body nor the actuator is normally repairable (they are not serviceable components with available internal spare parts), so the entire damaged component is replaced when it fails. The price of a complete new assembly with an actuator is generally a more favourable choice compared to the technician's labour and the risk of a recurring fault in an older part, than repeated partial repairs.

The exception is a situation where only the valve body itself is damaged and the actuator is demonstrably still working – in that case it is worth ordering just the standalone body without the actuator (see OT46) instead of the entire complete assembly, saving a significant part of the cost without any compromise in functionality.

Disposal of the Old Part

A replaced old valve or actuator is an electrical/metal component that does not belong in ordinary household waste. Hand it in at a collection yard or an electronic waste take-back point in your municipality, or ask your service technician about the option of handing it over directly during the replacement. Proper disposal contributes to the recycling of used metal and electronic materials.

Related Control and Pump Technology

The three-way valve is just one component of the hydraulic system around the boiler. For a more comprehensive service intervention or boiler room modernization, we also recommend checking the condition of other key components around the boiler – especially the circulation pump of the main heating circuit. Our range includes energy-efficient class A circulation pumps (EEI ≤ 0.20) in 130 mm and 180 mm installation lengths, including original OEM WILO Yonos PARA parts specifically for ATTACK boilers – replacing an old unregulated pump together with servicing the diverter valve is an efficient way to reduce electricity running costs during a single technician visit.

If your installation also uses a separate DHW tank, we recommend checking the condition of the tank's thermal insulation at the same time, as well as the priority setting between heating and DHW heating in the boiler's control unit – a correctly set priority ensures fast availability of hot water without unnecessarily limiting heating comfort.

Frequently Asked Questions

Is the actuator included in the price, or just the valve body?
Yes, this is a complete assembly including the motorized actuator, ready to be connected to the boiler control board.

Which ATTACK boilers is this part intended for?
For ATTACK boiler models and service ranges with low to medium output that use an external DHW tank and a 3/4" connection size.

What is the difference compared to OT02 (1")?
OT44 is the smaller 3/4" size for low to medium output, while OT02 is the larger 1" size for higher flow rates. The function is identical.

Is the FUGAS brand as good quality as Honeywell?
Yes, FUGAS is a proven brand of control technology commonly used as a fully equivalent alternative in smaller sizes of diverter valves.

Is the part supplied with mounting material?
Yes, the package includes union nuts and gaskets needed for standard installation on the 3/4" thread.

How do I test the function after replacement?
By forcing a DHW heating demand (e.g. by temporarily lowering and then raising the set tank temperature) and observing whether the valve visibly switches and the system starts heating the tank.

Is the part also suitable for smaller boilers with an output below 15 kW?
Yes, the 3/4" size is suitable precisely for the low to medium output range of boilers with an external DHW tank, including smaller models below 15 kW.

What if I'm not sure which size (OT02 vs. OT44) to order?
The most reliable way is to measure the connection thread of the original valve, or contact us with your boiler's serial number – we will gladly verify the correct size.

Are connection gaskets included in the package?
Yes, the complete assembly includes the gaskets needed for standard installation on the 3/4" thread.

Is the actuator of this valve as noisy as the larger OT02 size?
Yes, the operating principle and noise level of the actuator are comparable in both sizes, as it is the same type of motorized actuator adapted only to a different valve body size.

Can this valve be used with boilers without an external DHW tank?
No, this part only makes sense in installations with an external (separate) DHW tank requiring switching between the heating and charging circuits – it is not used with boilers that have their own instantaneous water heating.

Can the part be ordered with delivery to a construction site or directly to a service technician?
Yes, simply provide the required delivery address when ordering; we deliver anywhere in Slovakia using standard courier companies.

What is the procedure in the case of a claim?
Contact our customer service with proof of purchase and a description of the fault; we will be happy to advise on the next steps, including sending the part in for assessment if necessary.

Is the price shown including VAT?
Yes, all prices in our online store are shown including 23% VAT.

Can the part be ordered by phone or email, not just through the online store?
Yes, our customer service is also available by phone and email, and we are happy to help you choose the right part before ordering through the online store.

Do you also offer installation of this part, or only sales?
We do not carry out installation directly, as we are an online retailer. However, we are happy to recommend verified installation partners in your region.

Related Products

Also check out the larger size ATTACK Three-Way Valve HONEYWELL Complete 1" for higher output, or the standalone body without an actuator ATTACK Three-Way Valve Honeywell 3/4" type VC.

Summary

The ATTACK Three-Way Valve FUGAS Complete 3/4" is an affordable and reliable solution for switching between the heating circuit and an external DHW tank for boilers with low to medium output.

Warranty and Support

We provide a 24-month warranty from the date of dispatch from the warehouse for this product. When ordering a replacement, we recommend providing the serial number of your ATTACK boiler so that we can clearly verify the compatibility of the valve size and type with your specific model.