Saunier Duval Safety Limit Thermostat STY 300
Refurbished Saunier Duval Pressure gauges & aquastats

Saunier Duval Safety Limit Thermostat STY 300

If you notice that your boiler does not regulate the temperature properly or gets blocked due to a false lack of pressure, a technical diagnosis should confirm whether you 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. A technician should confirm through diagnosis whether it needs to be replaced when you observe these symptoms of malfunction.

Type of part
Pressure gauges & aquastats
Status
Refurbished
internal SKU
TLSSTY300
Warranty
1 year
VAT included Stock · 3 units
Compatibility

Compatible Saunier Duval boilers

Manometer. Seven confirmed compatibilities: STY 150 and STY 170.

Verified compatibility

Boiler modelFamilyVerification
Saunier Duval STY 150SecurityVerified
Saunier Duval STY 170SecurityVerified
Saunier Duval STY 220SecurityVerified
Saunier Duval STY 300SecurityVerified
Saunier Duval STY 400SecurityVerified
Saunier Duval STY 600SecurityVerified
Saunier Duval STY 800SecurityVerified

Can't see your model or have questions? The printed reference takes precedence. How to check it ·

Guide

How to check if it is the part for your boiler

The part reference, model, and equipment revision must be verified against the manufacturer's documentation.

  1. 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.
  2. Check the full boiler model on its data plate and look for it in the model associations on this page.
  3. Compare the connections and physical body with the original part before installation.
  4. If anything is unclear, send us a photo of the marking via WhatsApp before placing your order.
Diagnosis and fault codes

Symptoms that require diagnosis on the manometer

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.

Technical data

Saunier Duval pressure gauge datasheet

Uniclima internal SKU
TLSSTY300
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
Documentation

Manuals and technical documentation

Official documentation of the boiler, useful for locating the part and cross-referencing the fault codes.

Frequently asked questions

Frequently asked questions about the pressure gauge

Is this limit thermostat suitable for a Saunier Duval Security STY 300?
Yes, the Security STY 300 is on the list of compatible boilers, along with the rest of the STY range from 150 to 800.
What fault causes the Security STY 600 to turn off due to this thermostat?
The thermostat cuts off the supply when the temperature exceeds the safety limit, which causes the boiler to lock out.

Spare parts related to Saunier Duval Security

Delivery calculated by destination Delivery time shown at checkout
1-year warranty inspected and tested
14-day return uninstalled parts
Technical support we verify your model
Saunier Duval Safety Limit Thermostat STY 300