Underfloor heating (UFH) has become an increasingly popular choice in London homes, thanks to its sleek, space-saving design and energy efficiency. Whether installed in new builds or retrofitted into Victorian terraces, UFH can offer consistent warmth and improved comfort. However, as with any heating system, it can sometimes fail to operate as expected. One of the most frustrating issues for homeowners is when the underfloor heating simply doesn’t turn on.
In this article, we explore the most common reasons why underfloor heating systems may not activate, with a particular focus on homes in London. From simple user errors to more complex mechanical faults, we’ll help you identify the root of the problem and provide guidance on what steps to take next.
Types of Underfloor Heating Systems
Before diving into the issues, it’s important to know which type of underfloor heating system you have. There are two main types:
- Electric Underfloor Heating: Uses heating cables or mats laid under the floor surface. These are usually controlled by a dedicated thermostat.
- Water-Based (Hydronic) Systems: Circulate warm water through a network of pipes, connected to a boiler or heat pump, and often controlled via a manifold and zone system.
Understanding your system type is key to diagnosing any problems correctly.
Common Causes for Electric UFH Not Turning On
Thermostat Issues
The thermostat is often the first place to check. If the screen is blank, the batteries may be dead, or there may be a fault in the unit. Incorrect programming or settings can also prevent the system from turning on. Double-check that the thermostat is set to the correct mode and temperature.
Tripped Circuit Breaker
Electric underfloor heating is typically connected to a dedicated circuit. If this circuit trips due to a fault or overload, the system will stop working. Check your consumer unit (fuse box) to see if any breakers have tripped.
Wiring Problems
Wiring can become loose or damaged, particularly in homes where renovations or electrical work have recently taken place. Faulty wiring may require an electrician to inspect and repair the connections.
Damaged Heating Mats or Cables
Flooring work or heavy furniture may damage heating elements over time. This can result in cold spots or a complete system failure. If damage is suspected, a professional may use thermal imaging or resistance testing to pinpoint the issue.
Floor Sensor Failures
Some systems use floor sensors to regulate temperature. A faulty or disconnected sensor can prevent the heating from activating. Replacing the sensor or thermostat may resolve the issue.
Common Causes for Water-Based UFH Not Turning On
Boiler Issues
If the boiler isn’t firing up, the UFH won’t receive warm water. Check if the boiler is functioning normally and that it’s set to the right temperature. Also, check for error codes that might indicate a pressure or ignition problem.
Pump Malfunction
The circulation pump is essential for moving hot water through the system. If the pump is seized or silent, it may need to be reset or replaced. A buzzing or clicking sound may also indicate a pump fault.
Zone Valve Failure
Water-based systems often use zone valves to control different areas of the home. If a valve fails to open, water won’t flow to that zone. A failed actuator or motor can cause this.
Manifold Problems
Manifolds control the distribution of water across the heating loops. Blocked flow meters or stuck actuator heads can prevent heating from reaching certain zones.
Air in the System
Trapped air can cause the system to become unbalanced or prevent water from circulating. Bleeding the system (releasing air) can often restore normal function.
Faulty Thermostat or Controller
As with electric systems, the thermostat could be to blame. Ensure it’s communicating with the manifold and boiler correctly.
Factors Specific to London Homes
London’s housing stock is a unique mix of modern apartments and historical buildings. Each presents its own set of challenges:
- Older Homes: Victorian and Edwardian properties may have poor insulation or dated electrical systems that affect heating performance.
- Space Limitations: Compact properties may require tight installations, leaving little room for maintenance or inspection.
- Renovation Impact: Retrofitting UFH in existing buildings can lead to complications with subfloor conditions, pipework routing, and electrical supply.
These factors make professional installation and servicing particularly important in London.
Troubleshooting Tips Before Calling a Professional
Before picking up the phone, try these checks:
- Check the thermostat settings: Make sure it’s turned on, set to the right mode, and programmed correctly.
- Inspect the fuse box: Look for any tripped breakers or blown fuses.
- Test boiler operation: Ensure the boiler is heating water and showing no error messages.
- Feel the floor: Are there any warm spots? If not, the system may not be active.
- Look at the manifold: Are any indicators showing zero flow? Are actuators warm to the touch?
If after these checks the issue remains unresolved, it’s time to call in a heating engineer.
When to Call a Professional
If the problem involves electrical wiring, a malfunctioning boiler, or inaccessible components under the floor, a qualified professional is essential. In London, ensure they are registered with Gas Safe (for gas boilers) or NICEIC (for electrical work). Professionals have diagnostic tools like multimeters, thermal cameras, and system flush kits to resolve issues more efficiently.
Typical call-out charges in London can range from £80 to £150, but resolving the issue early can prevent more costly repairs down the line.
Preventative Maintenance Tips
To keep your UFH running smoothly:
- Schedule annual servicing for your boiler and UFH system.
- Regularly check thermostat functionality and settings.
- Monitor system pressure (for hydronic systems) and top up if necessary.
- Avoid placing heavy furniture directly over electric UFH mats.
- Keep records of your system layout for easy troubleshooting.
Related Questions
Why isn’t my underfloor heating system turning on?
Several factors can prevent your underfloor heating from activating. Common causes include a faulty thermostat, issues with the power supply, or problems with the heating elements or pipework. It’s essential to check that the thermostat is set correctly and that there are no tripped circuit breakers. If these components are functioning properly, the issue might lie within the heating system itself, such as airlocks in hydronic systems or damaged heating cables in electric systems.
What should I do if my underfloor heating isn’t producing heat?
First, ensure that your thermostat is operational and set to the desired temperature. For electric systems, verify that the heating cables are intact and receiving power. In hydronic systems, check for airlocks or blockages in the pipework, as these can impede water flow and heat distribution. If you’re unable to identify or resolve the issue, it’s advisable to consult a qualified heating engineer for a thorough inspection.
Can a faulty thermostat prevent my underfloor heating from working?
Yes, a malfunctioning thermostat can disrupt the operation of your underfloor heating system. If the thermostat fails to communicate with the heating elements or misreads the ambient temperature, it may not activate the system as needed. Replacing or repairing the thermostat often resolves such issues.
Conclusion
When your underfloor heating fails to turn on, it can feel like a major inconvenience, especially during cold London winters. Fortunately, many issues stem from common causes like thermostat errors, tripped circuits, or boiler faults. By understanding your system and performing a few simple checks, you can often identify the problem yourself.
For more complex issues, don’t hesitate to seek professional help. With the right maintenance and occasional servicing, underfloor heating remains one of the most efficient and comfortable ways to heat your home.
By staying proactive and informed, London homeowners can keep their UFH systems running effectively for years to come.