Boiler frequently goes into lockout during very cold weather but runs normally at milder temperatures.

Safety: Do not use open flames to thaw any lines. Turn off power if you suspect frozen components.

• Check outside terminations: Clear snow, ice, and frost from intake and exhaust. Ensure terminations are not buried.
• Inspect condensate line: Look for frozen sections, especially where the line runs outdoors or through unheated spaces. Thaw gently with warm towels or a hair dryer, then insulate and re-route if needed.
• Gas supply: If other gas appliances also struggle in cold weather, contact your gas supplier to check pressure.

If lockouts continue, a technician should evaluate venting, condensate routing, and gas supply sizing.