Vaillant vSMART Crossed Heating/DHW Control

Radiators heat up when only hot water is scheduled, or hot water heats when only heating is scheduled.

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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.

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Possible Causes

Miswired zone valves or diverter valve, incorrect assignment of vSMART outputs to heating and DHW, stuck diverter valve in boiler, configuration error in system type

How to Fix / Troubleshooting

Safety warning: Valve and boiler wiring should be handled by a qualified heating engineer.

Steps to narrow down:

  • Isolate schedules: Run a test with only heating scheduled, then only hot water scheduled, and observe which circuits heat.
  • Check configuration: In the app, verify that the system is configured correctly for combi or system boiler with cylinder, and that outputs are assigned properly.
  • Valve operation: A technician should check the motorized valves or internal diverter valve for correct operation and replace or rewire as needed.

Once wiring and valve control are corrected, vSMART will be able to control heating and hot water independently as intended.

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Repair Difficulty

Hard 4/5

Required Part

Diverter Valve / Motorized Zone Valves
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