Display shows E05; heater will not fire and may indicate rollout or flame safeguard issue.

Critical Safety Warning: Flame rollout indicates combustion gases may be escaping into the equipment area. Turn OFF power and gas immediately. Do not attempt to repeatedly reset the heater.

Visual checks (no disassembly of gas train):

• Inspect around burner compartment: Look for signs of scorching, melted wiring, or soot around the burner opening and front panel. If present, stop and call a technician.
• Check venting: From the outside, verify that the vent cap and flue outlet are not blocked by debris, nests, or snow. For sidewall-vented units, check both intake and exhaust terminations.
• Rollout switch reset: Some rollout switches are manual reset with a small button. After the unit is cool and the cause of rollout is addressed, you may press the reset. If it trips again, do not continue resetting.

Because rollout is a serious combustion fault, detailed inspection of the heat exchanger, burners, and vent system should be performed by a qualified Lochinvar service technician.