Underfloor heating faults usually trace back to one of a handful of causes, and which one depends heavily on whether your system is electric, hydronic (wet), or infrared. The good news: many issues are fixable rather than needing a full replacement.

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Common problems by system type

Electric underfloor heating

• Leaks, valve, or expansion vessel issues causing low pressure

• Cut or damaged heating cables preventing adequate heat

• A faulty valve actuator, often from a sticky pin

• Faulty wiring or a tripped circuit breaker

• A faulty thermostat causing incorrect readings or constant heating

• Trapped air reducing heat output and causing uneven heating

• Cables crossing or touching, which can cause damage and overheating; always keep cables at least 50mm apart

Infrared underfloor heating

• Circuit breaker issues cutting power

• Inconsistent wire spacing or floor levelling causing uneven heat

• Inadequate insulation wasting energy downwards instead of into the room

• Furniture blocking infrared radiation, reducing effectiveness

• Oddly shaped rooms sometimes needing the wattage split across two zones

Hydronic (wet) underfloor heating

• Trapped air blocking water flow, causing uneven or absent heating

• Pump or motor failure preventing proper circulation

• Debris or sediment blocking pipes, causing cold spots

• Leaks reducing pressure and heat output; watch for damp patches or a pressure drop

• Faulty pressure valves disrupting circulation

• A boiler not heating water properly (low pressure, thermostat issues) can affect the whole system; listen for unusual noises or inconsistent water temperature

If your underfloor heating works but running costs feel high, our guide on underfloor heating running costs explains what's normal for electric vs wet systems.

Quick checks to run yourself

• Is the thermostat working? Check batteries on wireless models

• Is it set to the correct temperature?

• Is the system getting power? Check for a tripped circuit breaker

• Any visible damage: leaks, exposed wires, damaged cables?

• Is the whole room cold, or just patches? This tells you if it's a zone-specific or system-wide issue

• Is the pump (wet systems) making unusual noises?

For electric systems specifically, you can also use a multimeter to test cable resistance and check for faults in the temperature sensor.

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Underfloor heating won't turn off

Usually a thermostat or control system issue:

1. Stuck relays in the control box

2. Wiring issues affecting the thermostat

3. Faults in actuators or zone valves

4. Incorrect thermostat settings; try resetting it, checking your manual for the exact steps

The first three point to electrical issues, so a heating engineer or electrician testing the circuits is the safest route.

Underfloor heating actuator problems

Actuators can fail in hydronic systems, causing inconsistent zone heating:

• A stuck actuator pin

• A failed actuator motor

• Stuck or blocked valves

• Wiring issues linked to the actuator

• The actuator not fully opening or closing

If a pin's stuck, try dislodging it gently with silicone spray or long-nose pliers. Beyond that, get a certified electrician or heating engineer to check the wiring and thermostat.

Underfloor heating pump not working

The circulator pump keeps hot water moving around a wet system. Common issues:

• Pump motor failure

• Air trapped in the pipes

• A clogged or blocked pump

• Incorrect pump speed settings

Try turning the pump off and checking whether pressure changes, which can point to a leak or blockage. Flushing the pipes or bleeding the system is worth trying too, or bring in a heating engineer.

Underfloor heating not working in one room

Usually a zone-specific issue:

• Trapped air in that zone's pipes

• A faulty actuator in that zone

• A blockage or leak specific to that area

• A thermostat issue in that room

To troubleshoot: check your boiler for common faults, check for a stuck valve actuator pin, check the thermostat (faults, battery, settings), try bleeding the system to clear trapped air, check for pressure issues in the filling loop and pipework, check wiring and connections, and check for leaks by re-pressurising zones one at a time.

Circulating pump installation cost guide

Got a faulty circulating pump making your heat and water tepid, at best? Find out the average cost to install a new recirculating pump here.

Learn more

Only attempt these checks if you feel genuinely comfortable doing so.

Before you call an engineer

• Note whether it's the whole system, one room, or won't turn off

• Check the thermostat: battery, settings, and basic function

• Check for a tripped breaker at the consumer unit

• For wet systems, check for pressure drops or unusual pump noise

• Avoid opening up wiring or actuators yourself if you're not confident

FAQs

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