Choosing the correct motorized valve actuator for a boiler isn’t just about picking the first part that looks right. The actuator controls the flow of water in response to heating demands — and the wrong choice can lead to inefficient heating, noise, premature wear or even system faults. This guide breaks down the key things to consider when selecting a motorized valve actuator so you get reliable operation and a good return on investment.
Whether you’re a Gas Safe engineer, a heating professional, a landlord with multiple properties, or a confident DIY homeowner, these practical tips will help you make the right choice.
What Is a Motorized Valve Actuator and Why It Matters
A motorized valve actuator is the component that moves the valve to open, close or modulate flow in your central heating system. It works with zone valves, diverter valves or midposition valves to control heating circuits and hot water demand. When the thermostat calls for heat, the actuator drives the valve to the correct position — and when the signal stops, it returns the valve to rest.
Without a correctly specified actuator, valves may not move at the right time or to the right position, leading to:
- Poor temperature control
- Uneven heating
- Boiler lockouts or fault codes
- Increased energy usage
Motorized actuators are small but essential — and selecting the right one can improve system performance and minimise costly callbacks.
Key Factors When Selecting a Motorized Valve Actuator
- Match the Actuator to the Valve Type
Not all actuators fit all valves. Valves come in different configurations:
- Twoport (on/off) valves — open or close fully
- Threeport / midposition valves — modulate flow between circuits
Ensure the actuator is designed for the specific valve type you’re fitting. A threeport actuator on a twoport valve (or viceversa) will not perform correctly.
- Check Voltage and Electrical Compatibility
Motorized valve actuators are available in different voltage ratings — commonly 230 V AC or 24 V for typical UK installations.
Always check:
- The boiler’s electrical supply
- The control signal voltage from the thermostat or controller
- Whether the actuator needs 230 V or lowvoltage control
Using the wrong voltage can damage the actuator or cause intermittent operation.
- Consider Actuator Speed and Torque
Not all actuators operate at the same speed or torque (turning force):
- Faster actuators can respond more quickly to thermostat calls
- Higher torque helps move valves that may be stiff or subject to debris
If a system has older valves that tend to stick, opting for an actuator with more torque can reduce stress and improve reliability.
- Look for Compatible Wiring and Connections
Actuator wiring should align with your control system:
- Common (C), Call for Heat (CH), Hot Water (HW) terminals
- Endswitches (if used for boiler interlock or pump control)
- Colourcoded or labelled connectors make installation easier
Check the boiler wiring diagram and the actuator’s wiring schematic before purchase.
- Choose Quality Parts – New or Remanufactured
Actuators endure frequent cycling as heating demands change. Lowquality actuators may fail early, leading to unnecessary callouts and unhappy customers.
At National Boiler Spares, we stock both new and remanufactured motorized valve actuators that:
- Are tested for reliable operation
- Meet relevant performance standards
- Offer a costeffective alternative with warranties
- Support environmental sustainability by extending part life
Refurbished actuators from reputable suppliers can be just as dependable as new units — provided they’ve been remanufactured to standard.
- Match Actuator Life Expectancy to Application
Consider the expected lifespan and duty cycle of the actuator:
- Commercial or highduty applications may require actuators rated for frequent cycles
- Smaller domestic systems with light usage can often use standard duty actuators
Thinking about expected usage prevents premature failures and reduces maintenance costs.
FAQs
Q: Can I fit any actuator to any valve?
A: No. Actuators must be compatible with the valve design (twoport vs midposition), voltage, and control wiring.
Q: What happens if the actuator is underspecified?
A: An underpowered actuator may fail to open fully, stick, or cause the valve to hunt (open/close repeatedly) — resulting in uneven heating and boiler errors.
Q: Are remanufactured actuators reliable?
A: Yes — when supplied by a trusted specialist like NBS, remanufactured actuators are rigorously tested and offer reliable performance at a lower cost.
Q: Should I replace the valve and actuator together?
A: It’s often good practice. If the valve body is worn or has debris, fitting a new actuator alone may not resolve underlying issues.
Q: Can I install an actuator myself?
A: Basic tasks like wiring and fitting should only be done by competent engineers or DIYers confident with electrical isolation and heating controls. When in doubt, consult a Gas Safe engineer.
Call to Action
Selecting the right motorized valve actuator can make all the difference to boiler performance and heating comfort. Visit our motorized valve actuators range at:
https://nationalboilerspares.co.uk/product-category/actuator-motors/
Our technical team can help you match the correct actuator to your valve and boiler model — including options for new or remanufactured parts that balance performance, cost and sustainability.
Contact us today for expert advice and fast delivery.
