Display shows LOC and boiler will not respond to thermostat calls or button presses.

Safety first: This is a control lock condition, not a combustion fault. You do not need to shut off gas, but if you will remove the front panel, switch off power at the service switch or breaker.

• Try unlocking the control: On many Laars boilers (e.g., Mascot, NeoTherm), press and hold the Up and Down arrow keys together for 5–10 seconds until LOC disappears. Check the user manual for the exact key combination.
• Check for stuck buttons: If LOC will not clear, gently press each keypad button several times. If a button feels stuck or does not click, the membrane keypad may be damaged.
• Power cycle the boiler: Turn off power for 30 seconds, then restore. If LOC clears temporarily and returns, a configuration or control board issue is likely.
• Installer lockout: Some Laars controls allow an installer lock. If the standard unlock sequence fails, contact the installer or a Laars-trained technician to access the installer menu and remove the lock.

When to call a professional: If the keypad is unresponsive, or LOC cannot be cleared with the documented sequence, the user interface or main control board may need replacement and should be handled by a qualified technician.