| Pilot Outage | Defective Thermocouple | Replace |
| Heavy Draft Blowing across Pilot | Redirect Air Movement or Eliminate |
| Plugged Pilot Orifice | Replace Orifice |
| No Gas | Check Manual Pilot Valve Check Main Gas Shut-Off Valve Check Manual Meter Valve Consult Gas Company |
| Defective Thermopilot Switch | Replace |
| Defective Ignition Control |
| Main Gas Valve Will Not Open (Spark Ignited Pilot) | No Power | Check Power Source with Meter Check Fuses |
| Defective Gas Valve | Replace |
| Low Water Level in Boiler or System Causing Low Water Cut-off to Function | Check for Leaks Check Feeder (if Supplied) |
| Defective Ignition Control | Replace |
| High Gas Pressure Switch Open (if Provided) | Check Switch Setting Check Manifold Gas Pressure |
| Low Gas Pressure Switch Open (if Provided) |
| Main Gas Valve Will Not Open (Standing Pilot) | No Power | Check Power Source with Meter Check Fuses |
| Defective Gas Valve | Replace |
| Pilot Out | Relight Pilot (May have defective pilot valve or relay) |
| Low Water in Boiler or System Causing Low Water Cut-off to Function | Check for Leaks Check Feeder (if Supplied) |
| Defective Thermopilot Switch | Replace |
| Defective Thermocouple |
| High Gas Pressure Switch Open (if Provided) | Check Switch Setting |
| Check Manifold Gas Pressure |
| Low Gas Pressure Switch Open (if Provided) | Check Switch Setting |
| Check Inlet Gas Pressure |
| Burner(s) Burning with Yellow Flame | Air Adjustment Screws Turned in Too Far | Adjust Screws Out |
| Low Gas Pressure in Manifold (Insufficient Air Injection) | Adjust Main Gas Pressure Regulator or Check Line Pressure |
| Burner Ports Partially Closed (Rust, Dirt, Lint, etc) | Replace Burners or Clean Ports |
| Insufficient Air for Combustion | Check Size of Combustion Air Openings to Room If Undersized, Correct as Required Check for Negative Pressure in Boiler Room |
| Oversized Burner Orifice | Install Correct Orifice |
| High Gas Pressure in Manifold | Adjust Main Gas Pressure Regulator |
| Gas Spillage from Draft Hood Relief Opening | Insufficient Draft - Chimney Too Low | Increase Height or Add Induced Draft Fan |
| Insufficient Draft - Chimney Too Small | Replace Chimney or Add Induced Draft Fan |
| Insufficient Draft - Blockage in Chimney or Vent | Repair Chimney or Vent |
| Insufficient Draft - Downdraft Caused by Chimney Location with Respect to Other Buildings, Roofs, etc. | Install Chimney Cap |
| Negative Pressure in Boiler Room (Due to Exhaust Fan or Duct System) | Remove Exhaust Fan or Isolate Fan From Boiler Room |
| Insufficient Combustion Air Openings | Provide Correctly Sized Combustion and Ventilation Air Openings |
| Main Gas Valve Opens But No Gas Flows | Manual Valve Closed at Gas Train | Open Valve |
| Manual Valve Closed at Meter |
| Test Firing Valve Closed (if Provided) |
| Water Hammer On Start-Up | Sags in Steam Piping or not enough Pitch | Correct Piping Condition |
| Concentric reducers causing condensate pooling | Correct Piping |
| Drip trap failed closed | Replace Trap or Trap Element |
| Dry returns wetted due to new boiler water line higher than old boiler | Correct Piping or Install Feed System and Traps |
| No drip line on the back side of a back-pitched motorized valve | Install Drip Line and Trap |
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| Water Hammer During Mid-Cycle | Clogged returns on gravity system | Clean or Re-Pipe Return Line(s) |
| Incorrect near-boiler piping causing wet steam to system | Correct Piping per Manual |
| Trap failed open, allowing steam to enter returns | Replace Trap or Trap Element |
| {Radiator Hammer} Large radiator may be vented too quickly | Use smaller Air Vent or Use Two Small Vents in Place of One Large Vent, One Mounted Higher than the Other |
| Long nipple at Hartford Loop | Replace with Close Nipple |
| Water leg or back slope in return line to receiver tank, causing water pocketing | Correct Piping |
| Trap installed at receiver tank, causing water trapping in return | Remove Trap at Tank, Install Drip Traps and Radiator Traps where Required |
| Boiler feed pump or condensate pump feed rate too fast, causing spraying into equalizer | Throttle Flow Rate |
| No drip on the inlet side of a forward pitched motorized valve | Add Drip Line and Trap |
| Uninsulated steam piping, causing excessive condensate loads | Insulate Steam Pipes |
| Water Hammer on Shut-Down | Close nipple on Hartford Loop too high | Repipe 2" to 4“ (5cm to 10cm) Below Water Line |
| Uninsulated steam piping in boiler room, but system piping insulated, causing vacuum condition on shut-down | Insulate Steam Pipes |
| Hammering in the Boiler | Poor circulation in the boiler due to sludge accumulation | Clean and Blowdown the Boiler |
| No Heat or Poor Heat Distribution in the Building | Main vents not working | Replace Main Vents, Repiping away from End of Lines if Needed |
| Drip Traps failed closed | Replace Traps or Trap Elements |
| Radiator traps failed open, allowing pressurization of the returns |
| Water legs or back slope in return lines to receiver tank, preventing air from venting out receiver vent | Correct Piping |
| Boiler pressure too high, causing air vents to lock up or blowing water loop seals | Reduce Operating Pressure |
| System or Boiler Overfilling or Flooding | New boiler water content smaller than old boiler | Install Boiler Feed System with Receiver Tank Large enough for Condensate |
| Boiler water feed rate or pump rate too fast causing water level to collapse (due to collapse of steam bubbles in boiler water) | Reduce Feed Rate |
| Foaming, priming or surging due to poor water quality | Clean the Boiler |
| Excessive Water Level Bounce | Poor water quality, causing foaming and surging |
| Incorrect near-boiler piping, such as undersized or incorrectly placed risers | Pipe per Manual |
| Boiler water feed rate or pump rate too fast | Reduce Feed Rate |
| Rapid Cycling | Air vents or traps not venting air, preventing steam from getting to radiation and pressurizing the air pocket | Replace Vents or Traps |
| Pressure differential on pressure control too close | Adjust Control Differential |
| Nuisance outages of water level control due to boiler water level bounce | See Excessive Water Level Bounce Above |