Thelia 623NC - Central heating boiler SAUNIER DUVAL - Free user manual and instructions
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| Product Type | Central heating boiler (condensing) |
| Brand | Saunier Duval |
| Model | Thelia 623NC |
| Fuel | Natural gas (G20) / Propane (G31) |
| Nominal Output | 23 kW |
| Efficiency | Up to 93% (condensing mode) |
| Dimensions (H x W x D) | 700 x 400 x 300 mm |
| Weight | 30 kg |
| Energy Class | A |
| Flue Type | Room sealed (balanced flue) |
| Maximum Flow Temperature | 80 °C |
| Minimum Flow Temperature | 30 °C |
| Gas Consumption (max) | 2.7 m³/h (G20) |
| Electrical Supply | 230 V / 50 Hz |
| Water Pressure Range | 1.0 - 2.0 bar |
| Noise Level | 50 dB(A) |
| Safety Devices | Overheat protection, frost protection, gas pressure switch |
| Maintenance | Annual service required |
| Warranty | 2 years |
| Country of Origin | France |
Frequently Asked Questions - Thelia 623NC SAUNIER DUVAL
How do I reset the Saunier Duval Thelia 623NC boiler after a fault?
Press and hold the reset button (usually a red or orange button on the front panel) for 3-5 seconds until the green light reappears. If the fault persists, contact a qualified technician.
What does error code E01 mean on my Thelia 623NC?
Error code E01 indicates a flame detection failure. Check that the gas supply is on and the isolation valve is open. If the problem continues, the ignition electrode or gas valve may need servicing.
How often should I service my Thelia 623NC boiler?
Saunier Duval recommends an annual service by a Gas Safe registered engineer to ensure efficiency and safety. This includes cleaning the heat exchanger and checking combustion.
Can I use the boiler with propane instead of natural gas?
Yes, the Thelia 623NC is compatible with propane (G31), but it requires conversion by a qualified professional. The gas type must be set via the parameters or a conversion kit.
How do I adjust the heating water temperature?
Use the control knob or digital interface on the boiler to set the desired flow temperature (typically between 30°C and 80°C). Refer to the manual for precise instructions.
Why is my boiler losing water pressure?
Low pressure (below 1.0 bar) may indicate a leak in the system or need for repressurisation. Check for visible leaks and use the filling loop to add water until pressure is between 1.0 and 2.0 bar.
How do I bleed the radiators with this boiler?
Turn the heating on and wait for the system to warm up. Using a radiator key, open the bleed valve on each radiator until water escapes, then close. Check boiler pressure afterwards.
What is the expected lifespan of the Thelia 623NC?
With proper annual maintenance, the boiler typically lasts between 10 and 15 years. Components like the fan or pump may require replacement during that time.
Is the Thelia 623NC suitable for underfloor heating?
Yes, it can be used with underfloor heating if the flow temperature is set low (e.g., 35-45°C). A mixing valve or weather compensator may be needed to avoid overheating.
How do I turn off the boiler for summer?
Switch the boiler to summer mode (if available) or turn off the heating function while leaving hot water mode active. Alternatively, shut off the power supply but leave gas on for safety.
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