Viadrus
Insufficient DHW Heating
Furnace runs but domestic hot water from the indirect cylinder is not hot enough or runs out quickly (on Viadrus systems with DHW cylinder).
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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
Faulty DHW NTC sensor, 3‑way diverter valve stuck in heating position, Scaled DHW coil in cylinder, Incorrect DHW temperature setting on Viadrus controller
How to Fix / Troubleshooting
Safety: Turn off power before working on valves or sensors.
- Check DHW setpoint: On the Viadrus controller, verify that the DHW temperature setpoint is high enough (e.g., 50–60°C).
- Test DHW sensor: Measure the resistance of the DHW NTC sensor and compare to the Viadrus chart. Replace if faulty.
- Inspect diverter valve: If a motorized 3‑way valve directs heat between heating and DHW, check that it moves when DHW is called. If stuck, replace the actuator or valve body.
- Descale coil: In hard water areas, the DHW coil in the cylinder may be scaled. A plumber can chemically descale the coil or replace the cylinder if necessary.
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Repair Difficulty
Medium
3/5
Required Part
3‑Way Diverter Valve Actuator
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