• The photocell is a flame-detection safety device, also known as a flame sensor, responsible for verifying flame presence during ignition and stable operation.
• If no flame is detected within the defined safety window, it triggers the burner’s RMO control box to enter lockout, preventing unsafe operation

2. Photocell Type & Construction

• RBL (Reflex Burner Light) photocells typically use a prismatic reflex glass sensor, detecting the flame via reflected infrared/visible light from the combustion chamber .
• Integrated into the combustion head, it fits in a dedicated housing, sealed and aligned to view the flame front.

3. Part Numbers & Compatibility

• While Riello’s manuals list photocells generically, OEM replacements (across 1G–4G models) typically use the same RBL-type unit.
• Aftermarket suppliers (e.g., Burner Bazaar) offer compatible models designed for Riello G-series (G5/G10/G20) and by extension, PRESS G burners. These operate at 230 V, 50 Hz, matching RMO control box sine output.

4. Electrical & Connection Specs

• Supply/Signal Voltage: Standard 230 V AC supply, 50 Hz, matching burner control.
• Control Interface: Wired to the RMO control box via the designated “FR” (Flame Relay) terminal. When the photocell detects flame, it closes the FR circuit, signaling “flame OK.”
• Typical resistance check: Sensor should show continuity (<1 kΩ); open circuit or reading >100 Ω typically indicates failure.

5. Installation & Maintenance Mounting

• Mounted on the combustion head in a sealed housing. Proper alignment and sealing prevent leakage and ensure accurate detection.

Cleaning & Inspection

• Must be kept clean and soot-free. Use non-abrasive cloth or cotton swab.
• Inspect the reflex glass for cracks or clouding; seal gasket integrity is critical.

Replacement Procedure

1. Power off and ensure cold burner.
2. Disconnect wiring at “FR” terminal.
3. Unscrew sensor assembly, replace with new RBL photocell.
4. Reinstall, align, and tight–fit gasket.
5. Reconnect wiring and restore power.
6. Perform full burner start-up cycle (pre-purge → ignition → flame monitoring → stable fire) to verify RMO sees flame and no premature lockout occurs.

Troubleshooting

• Remote ignition failure despite actual flame? Check photocell alignment, window clarity, or FR circuit continuity.
• Test tip: Temporarily disconnect photocell; if flame sustains longer than safety time (~12 seconds) before lockout, the photocell is likely faulty.

Summary Table