common faults of servomotors and their causes

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Actuators and valves form the heart of every modern heating system, yet their mechanical and electronic complexity is often the cause of unplanned outages. This article focuses on identifying the most common faults observed in practical applications on installation sites and offers specific solutions based on real maintenance intentions.

Incorrect valve size and actuator overload

One of the most common errors during installation is the mismatch between the system flow and the valve's kVS value, which causes the actuator to exert excessive effort to move the disc against the water pressure. If, for example, you choose a valve EUROMIX F4 3/4" kvs=6 for a system with high flow, the motor will try to open the valve, but the hydraulic resistance will stop it, causing the motor to overheat and eventually burn out the coil.

This phenomenon is often accompanied by noise during attempts to close or open and by the actuator quickly turning off after a few seconds of operation. Choosing the correct kVS value according to the hydraulic calculation is therefore the first step that prevents not only the actuator failure, but also the entire valve failure.

Coil burnout and electrical faults

Actuator coils are sensitive to voltage spikes and unstable power sources, which is a common problem with older control systems or with low-quality sockets without grounding. When connected for a long time to an incorrect voltage, for example 24V AC instead of 230V AC, it causes immediate overheating of the copper winding and its burning, which results in the complete failure of the actuator with no possibility of repair.

Another common cause is a broken phase or neutral wire due to a loose terminal, which causes the LED indication to flicker and the valve to move randomly. In such cases, it is always necessary to check the supply voltage with a multimeter and verify the tightness of the contacts in the box where the ROTODIVERT DN20 or another control valve is located.

Valve jamming and loss of sealing

Mechanical valve jamming is often caused by deposits in the system, corrosion of the disc, or drying of the lubricant in the threads, which prevents smooth movement under the pressure of the actuator. If the valve is not used regularly, for example during the summer months, it can lead to the sealing surfaces sticking together and the disc being unable to move even after a signal is given.

The solution to this problem is to manually release the valve using an Allen key at the end of the actuator, which removes the deposits and restores the seal. For long-term functionality, it is advisable to choose high-quality valves such as EUROMIX F4 1" kvs=10, which have more durable materials and better seals, or to implement regular maintenance.

Manually release the valve through the Allen key hole at the end of the actuator.
Clean the disc and seat from dirt and deposits.
Replace the seals and lubricate the threads with special lubricant.
Check the correct direction of water flow in the system.

Incorrect setting of positions and limits

A very common, yet easily fixable error is the incorrect setting of end positions, when the valve does not close completely or fails to reach the maximum opening, which affects temperature regulation. Actuators have internal potentiometers or sensors that must be calibrated to match the physical position of the valve from closed to open state.

Incorrect calibration is evident when the valve stops before reaching the desired state or, conversely, continues to move even after exceeding the mechanical stop, which leads to damage to the gear. The calibration process is simple and involves pressing the calibration button and waiting for a signal, while it is necessary to follow the time intervals specified in the manual.

Effect of humidity and corrosion on electronics

The electronics of actuators are very sensitive to humidity, which can get inside through leaky covers or through cabling, leading to oxidation of connections and short circuits. This is a common problem in areas with high humidity, such as bathrooms or basements, where there is insufficient ventilation.

Corrosive processes can affect not only the contacts, but also the metal parts of the actuator, which leads to reduced lifespan and increased risk of failure. Therefore, it is important to choose valves with protective covers and to ensure that all connections are in a protected environment, or alternatively use ROTODIVERT DN25 with higher resistance to the environment.

Tighten all covers and seals thoroughly before installation.
Use waterproof connectors and cable insulation.
Avoid installation in areas with direct water access.
Regularly check the condition of covers and seals.

Connection and Communication Errors

Communication problems between the control system and the actuator are often caused by incorrect phase conductor wiring or missing grounding, which leads to random movements or complete shutdown of the actuator. If phase is connected instead of neutral, or vice versa, the actuator may not respond to any signal and will remain in a safe mode.

Another common error is the use of an incorrect type of actuator for a given type of valve, for example, a 2-way valve with a 3-way actuator, which results in the inability to achieve the correct position. It is therefore critically important to follow the wiring diagram and verify the actuator type before installation to avoid unnecessary replacements and repairs.

Hydraulic imbalances and pressure spikes

In a system with an unbalanced hydraulic system, sudden pressure increases can occur that exceed the mechanical strength of the actuator gear. This phenomenon often occurs when the pump is started or when another valve in the network is suddenly closed, creating a pressure wave capable of damaging the plastic gears.

Frequently asked questions

How to determine whether the problem is in the motor or the coil?

By measuring the coil resistance, you can determine whether the circuit is broken (infinite resistance) or short-circuited (zero resistance), which indicates a burnt coil. If the coil has the correct resistance, but the valve does not move, the problem is likely in the mechanical transmission or in the motor itself.

Can I use a universal actuator on any valve?

No, each valve has a specific torque and rotation range, so it is necessary to select an actuator with the appropriate torque and type of connection to avoid damaging the valve or the actuator.

Why does the valve return to its original position after opening?

This phenomenon is caused by incorrect setting of the end positions or damage to the spring in the mechanism, which is supposed to keep the valve in the open position. Repair requires recalibration or replacement of the spring.

Profile diagnostics and timely reaction to these symptoms will help you avoid more expensive repairs and ensure smooth operation of your heating system. Regular inspection and correct installation are key factors that determine the lifespan of your equipment.

Do you have a question on this topic?

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