Potterton Safety Thermostat Inc. Cap COM17006955

The Potterton COM17006955 is a safety limit thermostat supplied with a capillary, listed as a TG400 cap with a 0.2 m capillary length. It forms part of the overheat protection circuit on Potterton gas boilers, cutting the burner when the sensed temperature exceeds the safe limit. It is used across the Osprey, Osprey 2 and Derwent Prestige PLUS appliance families.

• The boiler repeatedly locks out or trips on overheat during normal running.
• The burner fires and then shuts down before the system reaches temperature.
• No heating or hot water because the limit thermostat has latched out and will not reset.
• The capillary is kinked, crushed or corroded, giving inaccurate temperature sensing.
• The thermostat contacts no longer open or close correctly when tested.

• Confirm your boiler model against the fitment list above, as the same thermostat is used across several Osprey variants.
• Check the capillary length and routing on your appliance matches the 0.2 m capillary supplied.
• Compare the part number on the existing thermostat with COM17006955 before ordering.
• Inspect the mounting and phial pocket on the boiler for damage that may also need attention.