Unitech Combustion

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

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.

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.

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.

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

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.

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.

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

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.

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.

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.

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

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.

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.

Solenoid coils power the dual solenoid shutoff valves (V1 and V2) within the valve block, regulating staged fuel delivery: first-stage (low-fire) via V1, and second-stage (high-fire) via V2.

They operate on a 2-step voltage profile: high voltage (~29–30 V DC) during ignition to ensure rapid valve actuation, then a low holding voltage (~3 V DC) during steady operation to maintain the open position with minimal power consumption.

During ignition, the control box (RMO or equivalent) delivers the high voltage to swiftly open the valve, then reduces to a low holding voltage to sustain open status with minimal energy.

One commonly-used coil part number is 3002279 (~1 500 Ω), used across several G-series burners.

Another OEM coil for the PRESS G range is 3006714, listed as a solenoid coil oil burner coil used on GW/1G/2G/3G/4G models.

Mounting: Installed on the valve block assembly; ensure clean mounting surfaces and intact O‑rings/gaskets.

Wiring: Connected to the control box via dedicated terminals (e.g., “V1” and “V2”). Check for firm connections and good insulation.

Troubleshooting:

• If the coil is energized but oil flow does not begin, ensure high-voltage pulse is present during start—coils may stick if the initial voltage is missing.

• Measure resistance to confirm coil integrity (compare to ~1 500 Ω). Use a multimeter on DC current to verify high/low voltage switching during start and running phases.