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JK in-ground UFH Troubleshoot quick guide [pump not active]

Underfloor heating does not work (cold floor)

  1. Is the green LED (around the red dial) on the Wilo pump lit? If not, then go to step 2
  2. Ensure there is power supplied to the pump (check 2a, 2b);
    1. e.g. Is the wiring centre displaying a green or red light (manufacturer dependent)
    2. Is the pump powered directly into wall socket and have you checked for any problems with the fuse-board?
  3. Do you have water supply to manifold?
    1. Check that the left-hand pipe going into the manifold at the top is hot (CAUTION AS THIS IS VERY HOT. Do not grip the pipe firmly)
    2. Does the temperature gauge under the Wilo pump on the bottom leg (left) of the manifold indicate a temperature above 40°C?
    3. Is the return pipe on the manifold (top right) hot?
  4. Check actuators (if fitted)
    1. Ensure the actuators are all open (e.g. check that the red or black dot in the middle of each actuator is lifted approximately 3mm from the top)

Conclusion; IF ALL OF THE ABOVE IS CONFIRMED > the overheating protection is active, and the circulation pump cannot be activated. This is to prevent the floor from overheating or possibly causing damage to the floor finish.

To resolve this situation, follow these steps;

  1. Switch the heating system (boiler) completely off (at least 30 minutes, and check below)
  2. Check if the flow pipe to the manifold is cold (top left pipe above TRV)
  3. Check if the return pipe to the manifold is cold (top right pipe)
  4. Check if the temperature gauge (bottom left) indicates a temperature < 35°C
  5. Reduce TRV setting to 40°C maximum (or lower) and increase slowly (5°C in two days) once the system is in operation (see Step 3, page 3 JK’s Quick Start Manual)

Restart boiler/heating system, and demand heating for the underfloor heating zones. The green LED on the pump should switch on instantly

Picture above shows flow (left-hand side pipe – red) coming into the manifold (warm water) – blue, is the cold return water to the heat-source (e.g. combi boiler). The white unit attached to the flow pipe is an electronic zone-valve (two-way), this valve opens and closes the moment when the pump is being activated. The Green LED on the pump is not on (red arrow). See next picture.

The manifold above shows the green LED illuminated to indicate power. The red dots in the centre of the actuators are raised and the bottom temperature meter indicates 40°C. The bottom UFH pipes are warm, the top ones (blue lines) are cold. The return to the manifold is around 30 – 40°C, the flow is around 70°C.

The default situation can be caused by multiple aspects and are likely to be found outside of the underfloor heating system. Most common causes are;

  • Zone-valve not incorporated, and/or upstairs and downstairs heating is not separated in plumbing design, therefore hot water is supplied in all cases to the manifold the moment the boiler is activated and even when there is no demand for the underfloor heating system. (e.g. upstairs radiator or radiator zone demanding heat)
  • By-pass valve not incorporated in plumbing design. A mechanical by-pass valve can be incorporated into the boiler already. However, it is more likely that somewhere closer to the manifold a relief valve is incorporated. This allows the system to circulate and to release pressure – dissipate heat at all times - caused by supply (boiler) and (lower) demand by the manifold.
  • Return valve(s) on manifold are not completely open (see Quick Start Manual JK floorheating, Step 2, page 2)
  • TRV is not fitted correctly (no movement allowed, tightly fitted with spanner)
  • Overcapacity of the boiler. Reduce flow temperature to 60°C
Temperature dial bottom left manifold showing 34C
Green LED, pump setting no3 (right-hand-side)
Return valve completely open Setting TRV 35C on manifold (hex key no5)
Setting TRV 35C

Contact details

JK floorheating Ltd.

Unit 23, The Bell Centre, Newton Road

Crawley, West Sussex, RH10 9FZ

Company registration number: 10062935
VAT number: 237671390


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