Symptom Directory
Banging or Gurgling Pipes (Kettling / Air)
Noisy operation in pipes or boiler. Banging (water hammer or kettling from scale) or gurgling (trapped air in loop).
Read symptom guide → Professional Assessment Required (Call a Pro)Boiler Losing Water Pressure
System pressure gauge drops below 10–12 psi repeatedly. Causes include expansion tank diaphragm failure, relief valve discharge, hidden piping leak, or automatic fill valve failure.
Read symptom guide → Professional Assessment Required (Call a Pro)Boiler No Heat at All
Complete loss of heating across all zones. Causes include power loss, thermostat call failures, low water pressure lockout, gas supply interruption, or safety limit trips.
Read symptom guide → Professional Assessment Required (Call a Pro)Boiler Short-Cycling
Boiler turns on and off rapidly (cycles every few minutes) without satisfying space heat call. Causes include oversized boiler, insufficient buffer tank, low flow, or bad differential settings.
Read symptom guide → Safe for Homeowner ChecksOne Room or Zone is Cold
Specific zone or room fails to heat while others operate normally. Causes include stuck zone valves, failed zone circulators, thermostat wiring faults, or air trapped in loop.
Read symptom guide → Professional Assessment Required (Call a Pro)Ignition & Flame Failure Lockout (E-Codes / EA / F004 / 110)
Boiler attempts ignition but fails to detect flame, resulting in hard lockout. Causes include gas supply shutoff, dirty flame sensor electrode, vent blockage, or gas valve failure.
Read symptom guide → Professional Assessment Required (Call a Pro)Boiler Overheat & High-Limit Trip
Primary heat exchanger temperature exceeds high safety limit. Causes include zero fluid flow, air-bound primary loop, closed valves, failed circulator, or scaled heat exchanger.
Read symptom guide → Professional Assessment Required (Call a Pro)Temperature Sensor & NTC Faults
Boiler control detects open or short circuit on supply, return, or outdoor reset thermistors.
Read symptom guide → Professional Assessment Required (Call a Pro)Snowmelt System Not Melting
Driveway or walkway snowmelt fails to melt snow. Causes include sensor fault (slab moisture/temp sensor), low supply temp, glycol degradation, or insufficient BTU capacity.
Read symptom guide → Safe for Homeowner ChecksRadiant Floor Heats Unevenly
Cold spots or hot spots across radiant floor loops. Causes include unbalanced manifold flow, air pockets in loops, loop length imbalance, or wrong water temperature.
Read symptom guide →Safety Protocol & Guidance
Conservative Safety Classification
Hydronic boilers involve fuel gas combustion, high-voltage electrical circuits, high temperature water, and pressurized vessels. In accordance with Hydronic Authority safety standards, DIY homeowner checks are strictly limited to non-invasive tasks (such as checking thermostat batteries, visually checking pressure gauges, or adjusting radiator valves). Whenever a symptom involves combustion, gas pressure, internal electrical testing, or pressure vessel relief valves, homeowner checks are prohibited and professional technician service is required.