E5
Protherm
Boiler Flow Temperature Protection Error (via eBUS)
E5 error and thermostat indicates that minimum flow temperature or boiler protection limit has been violated.
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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
Incorrect minimum flow temperature configured, Faulty boiler flow sensor, Incompatible boiler parameter settings, Communication mismatch between thermostat and boiler
How to Fix / Troubleshooting
Safety: Boiler parameter changes should be performed by qualified personnel. Risk of scalding and equipment damage.
- Step 1 – Check thermostat heating curve / limits:
- In installer menu, review Heating curve and Min/Max flow temperature settings.
- Set within Protherm boiler’s recommended range.
- Step 2 – Verify boiler sensor status:
- Check boiler display for any flow temperature sensor errors.
- Resolve boiler-side sensor faults first.
- Step 3 – Synchronize parameters:
- Ensure both boiler and thermostat are configured for the same system type (radiators, underfloor, etc.).
- Step 4 – Reset both devices:
- Power cycle boiler and thermostat.
- Check if E5 clears.
- Step 5 – Professional service:
- If E5 persists, a Protherm technician should check boiler sensors and eBUS parameter mapping.
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Repair Difficulty
Hard
4/5
Required Part
Protherm Boiler Flow Temperature Sensor (interaction with thermostat)
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