Safety stops, holds and lockouts

What happens, in order

1. ILK string (internal low water cutoff and external limit on LIM) opens: Hold / Lockout 67
2. Outlet temperature at the high limit Hold / Lockout 79; installers can set the response to recycle and hold so the boiler does not lock out
3. Excess temperature rise or delta T across the boiler (usually low flow): Hold / Lockout 81 and 88
4. Flue temperature at the stack limit Lockout 82
5. Water going through the boiler backwards Hold / Lockout 85
6. Sensor open or shorted Hold 91 inlet, 92 outlet, 95 stack
7. Flame problems ignition failure Hold 110 or Lockout 109, flame circuit timeout Lockout 113, flame too low Lockout 138
8. Safety relay feedback wrong Lockout 174; reset power and replace the control if it comes back
9. After fixing the cause, clear the lockout from the display or cycle power
10. Check the lockout and alert history for what happened before the stop

Timings and thresholds

Codes you may see during this

Hold / Lockout 67, Hold / Lockout 79, Hold / Lockout 81, Lockout 82, Hold / Lockout 85, Hold / Lockout 88, Hold 91, Hold 92, Hold 95, Lockout 109, Hold 110, Lockout 113, Lockout 138, Lockout 174

Models

More NTI boiler sequences

• Combustion checking procedure · Startup
• Power-on and mode sequence · Startup
• Power-up and what lets the boiler start a call · Startup
• Failed ignition and lockout · Ignition
• First ignition start-up · Ignition
• Light-off sequence and retries · Ignition
• Central heat call (CH1) from call to satisfied · Heating
• Indirect tank (DHW) call · Domestic hot water