Klimosz Low Load / Flow Temperature Control Issue

Boiler cycles on and off rapidly when only a small underfloor heating zone is calling.

Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

No hydraulic separator between Klimosz boiler and UFH, Boiler minimum output too high, Incorrect mixing valve settings, Insufficient water volume in UFH loop

How to Fix / Troubleshooting

Safety: Hydraulic changes should be planned by a heating professional.

Check UFH mixing set: Ensure the underfloor heating mixing valve and pump are correctly set and that flow is adequate.
Adjust boiler output: Reduce the minimum and maximum heating output in the Klimosz controller within allowed limits.
Add buffer or separator: Consider installing a small buffer tank or hydraulic separator to decouple the boiler from the low-load UFH circuit.
Zone control: Group small zones or adjust control strategy to avoid very small active loads.

Repair Difficulty

Hard 4/5

Required Part

Hydraulic Separator / Buffer Tank

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