Saunier Duval Safety Limit Thermostat STY 300
If you notice that your boiler is not regulating the temperature properly or is blocking due to a false pressure drop, you may need a Saunier Duval STY 300 Safety Limit Thermostat. This part measures and controls the pressure and temperature of the circuit, ensuring adequate performance. The failure of this part results in incorrect readings that can affect the operation of your boiler. It is compatible with several models from the Security range, such as the STY 150, STY 170, STY 220, STY 400, STY 600, and STY 800, among others. You should replace it when you observe these symptoms of malfunction.
VAT included
Consult via WhatsAppCompatible Saunier Duval boilers
Manometer. Seven confirmed compatibilities: STY 150 and STY 170.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval STY 150 | Security | Contrasted |
| Saunier Duval STY 170 | Security | Contrasted |
| Saunier Duval STY 220 | Security | Contrasted |
| Saunier Duval STY 300 | Security | Contrasted |
| Saunier Duval STY 400 | Security | Contrasted |
| Saunier Duval STY 600 | Security | Contrasted |
| Saunier Duval STY 800 | Security | Contrasted |
Can't see your model or have questions? The printed reference takes precedence. How to check it · Send us a photo via WhatsApp.
How to check if it is the part for your boiler
What determines it is not the boiler model, but the reference printed on the part you already have installed.
- Find the reference printed on the installed part and check whether it matches the catalogue reference —. If it is not visible, do not identify the part by its shape alone.
- Check the full boiler model on its data plate and look for it in the model associations on this page.
- Compare the connections and physical body with the original part before installation.
- If anything is unclear, send us a photo of the marking via WhatsApp before placing your order.
Symptoms and faults that the manometer resolves
The manometer shows the pressure of the boiler circuit. These are the typical symptoms and what to do:
Common symptoms and faults
- 01
The boiler stops and needs to be reset by pressing a button for it to work again.
Cause: The safety limiter cuts the circuit when it detects a high temperature to prevent further damage.
Measure the water temperature with a thermometer: there may be a circulation problem and not an issue with the limiter.
- 02
The overtemperature cut-off triggers very frequently, even during normal use.
Cause: A misadjusted limiter or one with the bulb poorly attached to the pipe can trigger prematurely even if the boiler is not actually overheating.
Make sure that the bulb or sensor of the thermostat is securely attached and in firm contact with the pipe before considering it faulty.
- 03
The limiter trips without any apparent cause of overheating.
Cause: A damaged internal contact can open the circuit without the actual temperature justifying it.
Check that the circulation pump is working properly: if the water does not circulate, the area where the limiter is located may overheat.
These symptoms can have more than one cause. If your boiler displays a fault code, send it to us via WhatsApp along with a photo of the labeling, and we'll tell you if this is the part.
Saunier Duval pressure gauge datasheet
- Brand
- Saunier Duval
- Type of part
- Pressure gauges & aquastats
- Units in stock
- 3 units
- Status
- Refurbished
- Warranty
- 1 year
- Shipping
- Delivery time shown at checkout
- Return
- 14 days
Manuals and technical documentation
Official documentation of the boiler, useful for locating the part and cross-referencing the fault codes.
- Saunier Duval STY 220 Manual (PDF)Document © Saunier Duval, provided as a technical reference.
Frequently asked questions about the pressure gauge
Is this limit thermostat suitable for a Saunier Duval Security STY 300?
What fault causes the Security STY 600 to turn off due to this thermostat?
Spare parts related to Saunier Duval Security
