My boiler starts and then shuts off. Boilers are a vessel that heats up water to180 degrees if it’s a water boiler and approximately 912 degrees above 212 degrees if your boiler is a steam boiler.

My boiler starts then shuts off. Now many of the common boilers have 2 ignition systems.  Standing pilot ignition, (you should have a qualified boiler contractor to trouble shoot these issues).  However, this ignition is where you see a pilot in your boiler.  It’s located in the burner compartment usually attached to the burners with a bracket in the center of the burner compartment.

The standing pilot also uses a thermocouple that keeps the pilot-stat of the gas valve open constantly so when the thermostat calls for heat.  The gas valve opens allowing the natural gas to flow into the burners which ignites then heats up the boiler sections thus making the water in the boiler to get hot.

On the standing pilot system If my boiler starts and then shuts off the usual causes are a defective or shorting gas valve. A defective or weak burner or roll out limit, a bad thermostat if it’s the old round Honeywell t-87 f with the mercury actuated switch.

Sometimes the mercury bounces back and forth causing the burners to my boiler starts then shuts off symptoms.  Weak batteries in a digital thermostat can cause this occurrence as-well. If you have a standing pilot boiler more than likely it uses a Honeywell or White Rodgers relay control.  This control also can cause my boiler starts then shuts off symptom. In this instance you should have a qualified boiler repair expert to have a look see.

Grounding can be a possible issue with the boiler starting then shutting off. In this instance you would have a spark ignition system. You can verify your boiler ignition control by locating a black box on the outside panel down low near the gas valve.  Or in the burner compartment in the center of the panel.  The ignition control box colors are either black with a sticker with wording and numbers or the box may be grey with wording and numbers.

So, if your boiler starts and immediately shuts down then more than likely your boiler has a grounding issue.  However, a defective vent damper can cause this symptom due to the end switch failing or the end switch not stopping the vent motor.  These are a few causes why my boiler starts then shuts off. For assistance, please call us at 312-243-9896.