Viessmann 7825487 Fixed High Limit

The Viessmann 7825487 is a fixed high limit thermostat rated at 210°F / 99°C, produced for the WB2 appliance family. It acts as a non-adjustable safety cut-out, breaking the burner circuit when the sensed temperature reaches its fixed set point so the appliance cannot continue to run in an overheat condition. Because the limit is fixed rather than adjustable, the device is a direct safety component rather than a control thermostat.

• The appliance locks out or shuts down once it reaches temperature, with the fault recurring after every reset.
• Overheat or high limit fault codes appear on the control panel and cannot be cleared.
• The burner cuts out earlier than expected, before the appliance reaches its normal operating temperature.
• Continuity testing across the limit shows an open circuit when the sensor is cold.
• The limit trips repeatedly after the appliance has been running for a short period.

• Confirm the part number 7825487 against the label on the existing component or the appliance wiring diagram.
• Check the temperature rating on the failed part matches 210°F / 99°C, as limits for other appliance families are not interchangeable.
• Note the appliance model and serial number from the data plate so the correct variant can be verified.
• Inspect the mounting and any sealing washers on removal, as these may need to be replaced at the same time.