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Steps to Safety: Restarting Boilers After Summer Shutdown

Sept. 9, 2022
NBBI expert says entire system must be carefully checked and operating procedures reviewed before any boiler can be safely placed back into operation for fall and winter.

By ROBERT FERRELL, Senior Staff Engineer, National Board of Boiler and Pressure Vessel Inspectors (NBBI)

It’s that time of year when heating boilers should be prepared for the heating season.

Before moving the boiler power switch to the 'ON' position, survey the scene. I’ve taken that command from my first aid training. It means, “Before rushing in to help a victim, ensure you’re not the second victim.” Survey for potential hazards created by an improperly operating boiler or improperly stored material in the boiler room.

Your survey should ask the following questions: “What is the condition of the boiler system,” and “Has any work been performed on or near the boiler during the summer shutdown?”

If work has been done on or near the boiler, perform a system inspection tracing fuel lines, feed lines, steam and blow off piping, stack, and regulator vent lines. Check controls and control panels for evidence of damage and changes or loose connections. Inspect mechanical assemblies such as burner linkage and safety valve springs for paint, dirt, and rust accumulation which wouldn’t allow easy movement. Check all ventilation and combustion air openings are clean and free from debris.

Review the Manufacturer's Operation, Maintenance, and Instruction Manual for operation instructions. Become familiar with the timing sequence of the automatic controls. Then do a start-up check:

  • Verify water level in the boiler, and test the low water fuel cutoff; 
  • Verify the fuel train valve position;
  • Clean the flame scanner;
  • Verify peep sights on the burner and boiler are clean;
  • For steam boilers, verify operation of the feed/condensate system;
  • For water boilers, verify there is air in the expansion tank and make up water is available;
  • Verify electrical power is available to both the blower (power burners and induced draft) and control circuit.

Start the boiler by moving the power switch to ON. Reset all manual reset switches, low-water fuel cutoff (LWFC), fuel pressure switches, and pressure or temperature limits switches. Observe the start-up sequence. It may be necessary to isolate the boiler from the system to warm it up slowly.

Verify the flame conditions in the combustion chamber.

On gas fired non-condensing boilers, a cold start may produce condensate leaking from the gas pass covers and casing. Once the boiler water temperature exceeds 150° F, the condensate should stop.

Once the unit has warmed, turn power switch to 'OFF'. Verify the shut down cycle. Then restart. Let it come up to full firing rate and open isolation/ stop valves to put it into the system. Monitor it throughout the day, looking at the flame, stack outlet, controls, and linkage. Verify gasket tightness for both water side and fire side.

If any abnormal condition occurs during start-up, turn the power switch to 'OFF'. Investigate cause before restarting the boiler.


Based in Columbus OH, the author has more than 35 years of industry experience and a degree in mechanical engineering technology. He joined NBBI in 1999, where he serves as a senior staff engineer in its training department. This article was first published by NBBI in 2010 and has since been updated as needed.