Raypak ILO: Ignition Lockout
ILO means the heater has stopped trying to light on its own and is waiting for a manual reset before it will attempt ignition again.
If IGN already flashed once earlier and now the display reads ILO instead, that's the same underlying problem taking one more step: the heater has fully given up on lighting the burner and locked itself out until someone at the panel clears it. ILO tends to show up more on propane-fired Raypak units, where a lighter fuel supply or pilot-system quirk can make the ignition sequence fail more consistently than on natural gas.
Medium severityApplies to: Raypak Digital ASME and low-profile residential gas pool/spa heaters, particularly propane-fired units
What it means
Ignition Lockout — the heater has given up trying to light after repeated failed attempts and needs a manual reset. It's less a distinct fault type on its own and more the heater's way of saying "I already told you ignition wasn't working, and I'm not going to keep trying automatically" — the real problem is almost always whatever kept the burner from lighting in the first place.
Likely causes
- Underlying ignition failure (gas supply, igniter, or flame sensor) that hasn't been resolved
- Pilot/ignition assembly wear on propane-fired units
- Control board fault
What you can check yourself
- Clear the lockout at the front panel and allow one retry
- Confirm the gas supply and tank level before retrying
If ILO returns again after a single reset, don't keep cycling the reset — that just repeats a failed gas-ignition attempt. Have a licensed technician diagnose the underlying ignition fault.
Sources
Related
- All Raypak error codes
- Raypak IGN — the ignition failure that usually precedes an ILO lockout
- Hayward IF — Hayward's ignition-failure lockout on its gas heaters
- Pentair ERR IGN — Pentair's ignition control fault and lockout
- Pool Heater Won't Ignite — the cross-brand guide to burner ignition problems