Boiler shows E9 and shuts down, often with high temperature reading

Safety first: Do not reset an overheated boiler until it has cooled. Overheating can cause pressure buildup and scalding.

• Allow cooling: Turn off power and let the boiler cool to below 100°F before working on it.
• Check system flow: Verify that the circulator pump runs when there is a call for heat. Listen for operation and feel the piping for temperature change.
• Bleed air: Open air vents on radiators and near the boiler to remove trapped air that can stop circulation.
• Inspect strainers and valves: Clean any system strainers and confirm all isolation valves are open.
• Reset safety thermostat: Some Pennco boilers have a manual reset high-limit or safety thermostat on the boiler jacket. Press the reset button once the boiler is cool. If it trips again, do not continue resetting—have the cause diagnosed.