Potterton 404512 & Myson Ranco LO7-P1021 Overheat Thermostat

The Potterton 404512 is an overheat thermostat supplied as a boiler spare. It is a safety device that monitors temperature at its sensing point and breaks the circuit to the burner when the set limit is exceeded, preventing the appliance from running on past a safe operating temperature. It is listed under Potterton boiler spares and is identified by manufacturer code 404512.

• The boiler locks out or shuts down repeatedly once it has reached operating temperature.
• The appliance fires, runs briefly, then cuts out with a lockout that clears only after the boiler has cooled.
• A fault code relating to overheat or high limit is stored on the boiler controls.
• The boiler will not restart until it has been left to cool, then repeats the same cycle.
• The thermostat shows signs of heat damage, a distorted body or a loose or corroded connection.

• Check the appliance data badge and confirm the model and GC number against the compatibility list for this part number.
• Compare the part number on the existing thermostat with 404512 before removing it, as several thermostats are used across the Potterton range.
• Inspect any seal, gasket or retaining clip on removal and replace it if it is compressed, hardened or damaged.