No Heat at All
Complete diagnostic guide for underfloor heating systems producing no heat. Identify the cause and get your floor warm again.
Symptoms to Look For
Floor completely cold to touch
No warmth detected anywhere on the floor surface, even after extended runtime.
Thermostat shows heating mode but no response
Display indicates the system should be active, but nothing happens.
Boiler not firing when UFH calls for heat
The boiler doesn't ignite or respond to heating demand from underfloor system.
No power to UFH controller or wiring centre
Complete electrical failure with no lights or displays on control equipment.
Actuators not opening on manifold
Visual inspection shows actuators remain closed, preventing water flow.
Common Causes & Solutions
Tripped RCD or Blown Fuse
The most common cause. UFH systems draw significant current and can trip circuit protection.
Solution: Check consumer unit for tripped breakers. Reset if tripped. If it trips again immediately, call an electrician.
Thermostat Failure
Thermostats can fail electronically or lose communication with the wiring centre.
Solution: Check batteries on wireless stats. Try resetting the thermostat. If display is blank or showing errors, replacement may be needed.
Wiring Fault
Loose connections, damaged cables, or incorrect wiring can prevent the system from operating.
Solution: Visual inspection of wiring centre connections. Look for burnt terminals or disconnected wires. Professional diagnosis recommended.
Actuator Stuck Closed
Thermal or motorised actuators can seize in the closed position, blocking water flow to loops.
Solution: Check actuator LEDs/indicators. Try removing and refitting. Replace if faulty.
Boiler Interlock Issue
The UFH system may not be correctly calling the boiler for heat due to wiring or relay problems.
Solution: Check boiler responds to direct thermostat demand. Verify UFH wiring centre is correctly connected to boiler.
Failed Pump (Wet Systems)
Circulation pump may have failed or seized, especially after summer when not used.
Solution: Listen for pump noise. Check pump LED. Try freeing seized pump with screwdriver on impeller.
Step-by-Step Diagnosis
Check Power Supply
Verify the UFH system has power. Check RCD hasn't tripped and fuses are intact.
Inspect Thermostat
Ensure thermostat is set above room temperature and in heating mode. Check batteries if wireless.
Examine Wiring Centre
Look for LED indicators. Check all connections are secure. Note any error codes.
Check Actuators
Verify actuators are receiving power and opening. They should feel warm when active.
Verify Boiler Operation
Confirm boiler fires when UFH demands heat. Check interlock wiring.
Check Pump (Wet Systems)
Listen for pump operation. Feel manifold pipes for temperature difference.
Frequently Asked Questions
Related Faults
Need an engineer?
If this guide points to a fault you would rather not tackle yourself, our REFCOM-registered, F-Gas certified engineers cover London and the M25 with 24/7 emergency callout. Engineer time is £120 + VAT per hour with a written quote before any chargeable parts are fitted. Start with the relevant service below, or contact us for a site survey.