: If you have an external pump or a specialized ventilation system linked to your boiler, check if they are powered on and functioning. A tripped circuit breaker for an external pump often causes a D6 code. Inspect the Display Viessmann Fault Code Checker
For a heat pump compressor to run safely, a minimum volumetric flow of water must constantly circulate through the secondary condenser circuit. If the flow rate drops below the built-in threshold, the internal paddle switch or flow sensor opens. The heat pump throws a D6 fault to prevent the refrigerant loop from overheating or freezing the heat exchanger. Common Causes of the Boiler D6 Fault (EA1 Module Input DE1)
Several interconnected components can trigger a ventilation fault. The most common culprits include:
Verify fan and air supply
If resetting the boiler does not clear the D6 error, you must hire a Gas Safe registered engineer (or your local certified equivalent). Here is the diagnostic process they will follow:
Whether the fan makes any when you reset it.
Go outside and look at where your boiler flue exits the building.
If the reset does not work or if the D6 error appears frequently, you should contact a . A qualified technician will need to:
Over time, debris, sludge, and magnetite can accumulate in the system, clogging crucial components.
Before opening any casing on the boiler, ensure the power is isolated. If you are uncomfortable with electrical wiring, contact a Gas Safe registered engineer.
: If you have an external pump or a specialized ventilation system linked to your boiler, check if they are powered on and functioning. A tripped circuit breaker for an external pump often causes a D6 code. Inspect the Display Viessmann Fault Code Checker
For a heat pump compressor to run safely, a minimum volumetric flow of water must constantly circulate through the secondary condenser circuit. If the flow rate drops below the built-in threshold, the internal paddle switch or flow sensor opens. The heat pump throws a D6 fault to prevent the refrigerant loop from overheating or freezing the heat exchanger. Common Causes of the Boiler D6 Fault (EA1 Module Input DE1)
Several interconnected components can trigger a ventilation fault. The most common culprits include: viessmann d6 error
Verify fan and air supply
If resetting the boiler does not clear the D6 error, you must hire a Gas Safe registered engineer (or your local certified equivalent). Here is the diagnostic process they will follow: : If you have an external pump or
Whether the fan makes any when you reset it.
Go outside and look at where your boiler flue exits the building. If the flow rate drops below the built-in
If the reset does not work or if the D6 error appears frequently, you should contact a . A qualified technician will need to:
Over time, debris, sludge, and magnetite can accumulate in the system, clogging crucial components.
Before opening any casing on the boiler, ensure the power is isolated. If you are uncomfortable with electrical wiring, contact a Gas Safe registered engineer.