Ruud Boilers Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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E0
Boiler display shows E0 and the unit will not fire; the control is unresponsive or intermittently resets.
Control Board Communication / Internal Fault
E1
Boiler shows E1 and will not ignite; the burner never lights, and you may hear only a brief click.
Ignition Failure / Ignition Lockout
E10
Boiler displays E10 and shuts down; may be associated with condensate in the venting
Condensate Drain / Trap Fault
E11
Boiler shows E11 and will not fire; fan may not start
Inducer Fan / Combustion Blower Fault
E12
Boiler displays E12; may occur during operation with strong wind or venting issues
Flue Gas / Draft Fault
E13
Boiler shows E13 and locks out; may be associated with outdoor reset operation
Outdoor Temperature Sensor Fault
E14
Boiler displays E14; may not respond correctly to domestic hot water demand (on combi models)
DHW Temperature Sensor Fault
E15
Boiler shows E15 and will not fire; may occur after thermostat wiring changes
Thermostat / Call for Heat Input Fault
E16
Boiler displays E16; the pump may not run or may run continuously.
Circulator Pump Control Fault
E17
Boiler shows E17 and may short-cycle or fail to modulate correctly.
Flow Sensor / Flow Switch Fault (Combi or Modulating Models)
E18
Boiler displays E18; it may be associated with gas valve operation.
Gas Valve Control Fault
E19
Boiler shows E19 and may not modulate; the flame may be unstable.
Gas Valve Modulation / Fan Speed Coordination Fault
E2
Boiler displays E2 and shuts down shortly after starting; the burner may light briefly then go out.
Flame Loss / Flame Signal Fault
E20
Boiler displays E20; it may be associated with internal communication between modules.
Internal Communication Fault (e.g., Display to Main PCB)
E3
Boiler shows E3 and will not start; the fan may run briefly then stop.
Pressure Switch / Air Proving Fault
E4
Boiler displays E4 and shuts down; this may occur after running for a short period.
High Limit / Overheat Lockout
E5
Boiler shows E5 and will not fire; this may occur immediately on a call for heat.
Low Water Pressure / Low Water Cutoff Fault
E6
Boiler displays E6; unit may run erratically or not at all
Supply Temperature Sensor Fault (NTC Open/Short)
E7
Boiler shows E7; may not respond correctly to return water temperature
Return Temperature Sensor Fault (NTC Open/Short)
E8
Boiler displays E8 and shuts down; may be accompanied by gurgling sounds in the heat exchanger
Outlet Over‑Temperature / Heat Exchanger Overheat
E9
Boiler shows E9 and will not operate; may occur after a power event or wiring work
Internal Control Error / Configuration Fault
Symptom
Boiler display is blank or unreadable, but the unit may still operate.
Display / User Interface Failure
Symptom
Boiler emits unusual odors (burning, metallic, or exhaust smell) during operation.
Combustion / Venting Issue
Symptom
Boiler fan runs but the burner never lights; no error code is displayed.
Ignition Sequence Interruption
Symptom
Boiler frequently locks out and must be manually reset at the control.
Repeated Safety Lockouts
Symptom
Boiler frequently loses pressure and needs to be topped up with water.
Chronic Pressure Loss / System Leak
Symptom
Boiler ignites but shuts down after a few seconds; it may retry several times.
Flame Proving / Flame Stability Issue
Symptom
Boiler is excessively noisy (rumbling, whistling, or vibrating) during operation.
Mechanical Vibration / Combustion Noise
Symptom
Boiler pressure rises excessively during heating, and the relief valve discharges water.
Expansion Control / Over‑Pressurization
Symptom
Boiler produces no domestic hot water on a combi model, but space heating works.
DHW Production Failure (Combi Boiler)
Symptom
Boiler runs continuously and overshoots the thermostat setting; the house becomes too warm.
Control / Thermostat Runaway
Symptom
The boiler does not respond to thermostat call; the thermostat appears to work, but the boiler stays off.
No Call for Heat Recognition
Symptom
The boiler frequently goes into warm-weather shutdown even when heat is still needed.
Outdoor Reset / Warm Weather Shutdown Misconfiguration
Symptom
The boiler makes loud banging or knocking noises (kettling) during operation.
Kettling / Boiling in Heat Exchanger
Symptom
The boiler or nearby piping is leaking water onto the floor.
System Water Leak
Symptom
The boiler runs but does not heat the house adequately; radiators or baseboards are lukewarm.
Insufficient System Flow / Under-Circulation
Symptom
The boiler short-cycles (turns on and off frequently) without maintaining a steady temperature.
Short Cycling / Control or Sizing Issue
Symptom
The boiler starts normally but shuts down when multiple zones call for heat.
Flow / Load Imbalance Under Multi-Zone Demand
Symptom
The boiler will not start at all; there are no lights or display, it is completely dead.
No Power / Line Voltage Supply Failure
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| E0 |
Boiler display shows E0 and the unit will not fire; the control is unresponsive or intermittently resets.
|
Control Board Communication / Internal Fault | View Details |
| E1 |
Boiler shows E1 and will not ignite; the burner never lights, and you may hear only a brief click.
|
Ignition Failure / Ignition Lockout | View Details |
| E10 |
Boiler displays E10 and shuts down; may be associated with condensate in the venting
|
Condensate Drain / Trap Fault | View Details |
| E11 |
Boiler shows E11 and will not fire; fan may not start
|
Inducer Fan / Combustion Blower Fault | View Details |
| E12 |
Boiler displays E12; may occur during operation with strong wind or venting issues
|
Flue Gas / Draft Fault | View Details |
| E13 |
Boiler shows E13 and locks out; may be associated with outdoor reset operation
|
Outdoor Temperature Sensor Fault | View Details |
| E14 |
Boiler displays E14; may not respond correctly to domestic hot water demand (on combi models)
|
DHW Temperature Sensor Fault | View Details |
| E15 |
Boiler shows E15 and will not fire; may occur after thermostat wiring changes
|
Thermostat / Call for Heat Input Fault | View Details |
| E16 |
Boiler displays E16; the pump may not run or may run continuously.
|
Circulator Pump Control Fault | View Details |
| E17 |
Boiler shows E17 and may short-cycle or fail to modulate correctly.
|
Flow Sensor / Flow Switch Fault (Combi or Modulating Models) | View Details |
| E18 |
Boiler displays E18; it may be associated with gas valve operation.
|
Gas Valve Control Fault | View Details |
| E19 |
Boiler shows E19 and may not modulate; the flame may be unstable.
|
Gas Valve Modulation / Fan Speed Coordination Fault | View Details |
| E2 |
Boiler displays E2 and shuts down shortly after starting; the burner may light briefly then go out.
|
Flame Loss / Flame Signal Fault | View Details |
| E20 |
Boiler displays E20; it may be associated with internal communication between modules.
|
Internal Communication Fault (e.g., Display to Main PCB) | View Details |
| E3 |
Boiler shows E3 and will not start; the fan may run briefly then stop.
|
Pressure Switch / Air Proving Fault | View Details |
| E4 |
Boiler displays E4 and shuts down; this may occur after running for a short period.
|
High Limit / Overheat Lockout | View Details |
| E5 |
Boiler shows E5 and will not fire; this may occur immediately on a call for heat.
|
Low Water Pressure / Low Water Cutoff Fault | View Details |
| E6 |
Boiler displays E6; unit may run erratically or not at all
|
Supply Temperature Sensor Fault (NTC Open/Short) | View Details |
| E7 |
Boiler shows E7; may not respond correctly to return water temperature
|
Return Temperature Sensor Fault (NTC Open/Short) | View Details |
| E8 |
Boiler displays E8 and shuts down; may be accompanied by gurgling sounds in the heat exchanger
|
Outlet Over‑Temperature / Heat Exchanger Overheat | View Details |
| E9 |
Boiler shows E9 and will not operate; may occur after a power event or wiring work
|
Internal Control Error / Configuration Fault | View Details |
| – |
Boiler display is blank or unreadable, but the unit may still operate.
|
Display / User Interface Failure | View Details |
| – |
Boiler emits unusual odors (burning, metallic, or exhaust smell) during operation.
|
Combustion / Venting Issue | View Details |
| – |
Boiler fan runs but the burner never lights; no error code is displayed.
|
Ignition Sequence Interruption | View Details |
| – |
Boiler frequently locks out and must be manually reset at the control.
|
Repeated Safety Lockouts | View Details |
| – |
Boiler frequently loses pressure and needs to be topped up with water.
|
Chronic Pressure Loss / System Leak | View Details |
| – |
Boiler ignites but shuts down after a few seconds; it may retry several times.
|
Flame Proving / Flame Stability Issue | View Details |
| – |
Boiler is excessively noisy (rumbling, whistling, or vibrating) during operation.
|
Mechanical Vibration / Combustion Noise | View Details |
| – |
Boiler pressure rises excessively during heating, and the relief valve discharges water.
|
Expansion Control / Over‑Pressurization | View Details |
| – |
Boiler produces no domestic hot water on a combi model, but space heating works.
|
DHW Production Failure (Combi Boiler) | View Details |
| – |
Boiler runs continuously and overshoots the thermostat setting; the house becomes too warm.
|
Control / Thermostat Runaway | View Details |
| – |
The boiler does not respond to thermostat call; the thermostat appears to work, but the boiler stays off.
|
No Call for Heat Recognition | View Details |
| – |
The boiler frequently goes into warm-weather shutdown even when heat is still needed.
|
Outdoor Reset / Warm Weather Shutdown Misconfiguration | View Details |
| – |
The boiler makes loud banging or knocking noises (kettling) during operation.
|
Kettling / Boiling in Heat Exchanger | View Details |
| – |
The boiler or nearby piping is leaking water onto the floor.
|
System Water Leak | View Details |
| – |
The boiler runs but does not heat the house adequately; radiators or baseboards are lukewarm.
|
Insufficient System Flow / Under-Circulation | View Details |
| – |
The boiler short-cycles (turns on and off frequently) without maintaining a steady temperature.
|
Short Cycling / Control or Sizing Issue | View Details |
| – |
The boiler starts normally but shuts down when multiple zones call for heat.
|
Flow / Load Imbalance Under Multi-Zone Demand | View Details |
| – |
The boiler will not start at all; there are no lights or display, it is completely dead.
|
No Power / Line Voltage Supply Failure | View Details |
No matching codes found
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